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Background: In the prehospital triage of patients presenting with symptoms suggestive of acute myocardial ischemia, reliable myocardial ischemia detection in the electrocardiogram (ECG) is pivotal. Due to large interindividual variability and overlap between ischemic and nonischemic ECG-patterns, incorporation of a previous elective (reference) ECG may improve accuracy. The aim of the current study was to explore the potential value of serial ECG analysis using subtraction electrocardiography., Methods: SUBTRACT is a multicenter retrospective observational study, including patients who were prehospitally evaluated for acute myocardial ischemia. For each patient, an elective previously recorded reference ECG was subtracted from the ambulance ECG. Patients were classified as myocardial ischemia cases or controls, based on the in-hospital diagnosis. The diagnostic performance of subtraction electrocardiography was tested using logistic regression of 28 variables describing the differences between the reference and ambulance ECGs. The Uni-G ECG Analysis Program was used for state-of-the-art single-ECG interpretation of the ambulance ECG., Results: In 1,229 patients, the mean area-under-the-curve of subtraction electrocardiography was 0.80 (95%CI: 0.77-0.82). The performance of our new method was comparable to single-ECG analysis using the Uni-G algorithm: sensitivities were 66% versus 67% (p-value > .05), respectively; specificities were 80% versus 81% (p-value > .05), respectively., Conclusions: In our initial exploration, the diagnostic performance of subtraction electrocardiography for the detection of acute myocardial ischemia proved equal to that of state-of-the-art automated single-ECG analysis by the Uni-G algorithm. Possibly, refinement of both algorithms, or even integration of the two, could surpass current electrocardiographic myocardial ischemia detection., (© 2019 The Authors. Annals of Noninvasive Electrocardiology published by Wiley Periodicals, LLC.)

Objectives: This study sought to evaluate the relation between 12-lead ventricular tachycardia (VT) electrocardiography (ECG) and VT-related anatomical isthmuses (AIs) in repaired tetralogy of Fallot (rTOF)., Background: Slow-conducting AIs are the dominant VT substrate in rTOF. Whether an AI is considered critical relies on pace mapping (PM) guided by the VT ECG., Methods: VT ECGs, electroanatomical mapping data and PM results were analyzed in 25 rTOF patients (group 1) (age 57 ± 13 years). Selection of PM and ablation sites was guided by VT ECG. In 7 patients (group 2) (age 33 ± 14 years), PM was systematically performed within all AIs, irrespective of the VT ECG., Results: In group 1, all 35 induced VTs (median VT cycle length 270 [interquartile range: 240 to 310] ms) were AI related. All 11 right bundle branch block (RBBB) VTs were related to AI3 (right ventricular septum if positive concordant [7 of 7]), coronary cusp if V2 transition break [3 of 4]). Left bundle branch block (LBBB) VTs with transition 

Objectives: This study sought to evaluate the influence of slow conducting anatomic isthmuses (SCAI) as dominant ventricular tachycardia (VT) substrate on QRS duration., Background: QRS prolongation has been associated with VT in repaired tetralogy of Fallot., Methods: Seventy-eight repaired tetralogy of Fallot patients (age 37 ± 15 years, 52 male, QRS duration 153 ± 29 ms, 67 right bundle branch blocks [RBBB]) underwent programmed stimulation and electroanatomic activation mapping during sinus rhythm. Right ventricular (RV) surface, RV activation pattern, RV activation time, conduction velocity at AI, and remote RV sites were determined., Results: Twenty-four patients were inducible for VT (VT+); SCAI was present in 22 of 24 VT+ but only in 2 of 54 patients without inducible VT (VT-). Conduction velocity through AI was slower in VT+ patients (median of 0.3 [0.3 to 0.4] vs. 0.7 [0.6 to 0.9] m/s; p < 0.01) but conduction velocity in the remote RV did not differ between groups. In non-RBBB, QRS duration was similar in VT+ patients (n = 6) and VT- patients (n = 5), but RV activation within SCAI exceeded QRS offset in VT+ patients (37 ± 20 ms vs. -5 ± 9 ms, p < 0.01). In RBBB, both QRS duration and RV activation time were longer in VT+ patients (n = 18, 17 of 18 QRS > 150 ms) compared with VT- patients (n = 49, 27 of 49 QRS > 150 ms) (173 ± 22 ms vs. 156 ± 20 ms; p < 0.01; 141 ± 22 ms vs. 129 ± 21 ms; p = 0.04). In VT+ patients, QRS prolongation >150 ms (n = 17) was due to SCAI or blocked isthmus in 15 patients (88%) and 1 (6%). In contrast, in VT- patients, QRS prolongation >150 ms (n = 27) was due to enlarged RV or blocked isthmus in 10 patients (37%) and 8 (30%), but due to SCAI in only 1 (4%). After exclusion of a severely enlarged RV, a QRS duration >150 ms was highly predictive for SCAI/blocked AI (OR: 17; 95% CI: 3.3 to 84; p < 0.01)., Conclusions: A narrow QRS interval does not exclude VT-related SCAI. In the presence of RBBB, SCAI further prolongs QRS duration. QRS duration >150 ms is highly suspicious for SCAI or isthmus block distinguishable by electroanatomic mapping., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Recently published randomised clinical trials indicate that prolonged electrocardiom (ECG) monitoring might enhance the detection of paroxysmal atrial fibrillation (AF) in cryptogenic stroke or transient ischaemic attack (TIA) patients. A device that might be suitable for prolonged ECG monitoring is a smartphone-compatible ECG device (Kardia Mobile, Alivecor, San Francisco, CA, USA) that allows the patient to record a single-lead ECG without the presence of trained health care staff. The MOBILE-AF trial will investigate the effectiveness of the ECG device for AF detection in patients with cryptogenic stroke or TIA. In this paper, the rationale and design of the MOBILE-AF trial is presented., Methods: For this international, multicentre trial, 200 patients with cryptogenic stroke or TIA will be randomised. One hundred patients will receive the ECG device and will be asked to record their ECG twice daily during a period of 1 year. One hundred patients will receive a 7-day Holter monitor., Discussion: The primary outcome of this study is the percentage of patients in which AF is detected in the first year after the index ischaemic stroke or TIA. Secondary outcomes include markers for AF prediction, orally administered anticoagulation therapy changes, as well as the incidence of recurrent stroke and major bleeds. First results can be expected in mid-2019., Trial Registration: ClinicalTrials.gov, ID: NCT02507986 . Registered on 15 July 2015.

Aging is associated with changes in left atrial (LA) structure and function. The present study aimed at describing the effect of aging on LA properties in a large cohort of subjects without structural heart disease. We divided 386 subjects (mean age 58 years [range 16 to 91]; 188 men [49%]) clinically referred for echocardiography according to age groups. The P-wave dispersion (PWD), reflecting total atrial conduction time, was measured on a 12-lead surface electrocardiogram as the difference between maximum and minimum P-wave duration. The PA-TDI duration reflecting the total atrial conduction time was measured on tissue Doppler imaging (TDI) as the time between onset of P wave on surface electrocardiogram to peak A'-wave velocity. Two-dimensional speckle-tracking echocardiography was used to assess LA reservoir function, reflecting LA compliance. In the overall population, mean PWD, PA-TDI, and LA reservoir strain were 43 ± 12 ms, 129 ± 27 ms, and 36 ± 13%, respectively. Increasing age was independently associated with prolonged PWD (β = 0.161; p <0.001), PA-TDI (β = 0.476; p <0.001), and reduced LA reservoir strain (β = -0.259; <0.001), suggesting age-related fibrotic changes of the LA myocardium. The association between age and LA reservoir strain was modulated by body mass index (β = -0.582; p <0.001) and LA volume index (β = -0.117; p = 0.014). In conclusion, aging is associated with longer PWD and PA-TDI duration along with a decrease in LA reservoir function. Obesity and larger LA volumes are independently associated with reduced LA compliance., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: The aim was to assess the diagnostic value of the Inverse Dower (INVD)-derived vectorcardiogram (VCG) and the Kors-derived VCG to detect elevated systolic pulmonary artery pressure (SPAP) in suspected pulmonary hypertension (PH)., Methods: In 132 patients, morphologic variables were evaluated by comparing the VCG parameters synthesized by INVD and Kors matrix. Comparison of the diagnostic accuracy of detecting SPAP ≥50mmHg between the matrices was performed by ROC curve analysis and logistic regression analysis., Results: Most VCG parameters differed significantly between INVD and Kors. ROC analysis for detection of SPAP ≥50mmHg by VG projected on the X-axis demonstrated no difference (p=0.99) between INVD (AUC=0.80) and Kors (AUC=0.80). Both the INVD- and Kors-derived VCG provided significant diagnostic information on the presence of SPAP ≥50mmHg (INVD, OR 1.05, 95%CI 1.03-1.07; P<0.001; Kors, OR 1.05, 95%CI 1.03-1.08; P<0.001)., Conclusion: Although there were significant differences in measures of vector morphology, both INVD- and Kors-derived VCG demonstrated equal clinical performance in case of elevated SPAP., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: There is no consensus about the time instant relative to the J point where ST deviation has to be measured for detection of acute ischemia in the ECG., Methods: We analyzed 53 ECGs, recorded preceding emergency catheterization of acute coronary syndrome patients with a completely occluded culprit artery (cases), and 88 control ECGs recorded in the cardiology outpatient clinic. ECG-amplitude measurements were made every 10 ms, between 20 ms before till 80 ms after the J point. STEMI-detection algorithms varied from the traditional STEMI criterion (elevations in at least two adjacent ECG leads), via the STEMI equivalent criterion (depressions in V2 and V3), to the most liberal STEMI-detection algorithm in which elevations as well as depressions in two adjacent leads were considered as signs of ischemia., Results: Diagnostic accuracy was highest (93.6%) for the most liberal STEMI-detection algorithm at 10 ms after the J point; sensitivity was 94.3% and specificity was 93.2%., Conclusion: The results of our study suggest that STEMI detection close to the J point is optimal., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The Seattle Heart Failure Model (SHFM) provides accurate estimates of survival in heart failure (HF) patients. The model is, however, not developed for HF patients with cardiac resynchronization therapy (CRT). The aim of this study was to assess the prognostic value of SHFM combined with QRS morphology and CRT-related change in QRS duration in implantable cardioverter defibrillator (ICD) and CRT defibrillator (CRT-D) recipients., Methods: All patients who underwent prophylactic ICD implantation at the Leiden University Medical Center since 1996 were included. Baseline SHFM, QRS morphology, and duration before and after device implantation were determined. The regression coefficients of the QRS characteristics derived from a Cox regression analysis were implemented in the SHFM. SHFM-estimated survival was compared with Kaplan-Meier observed survival., Results: The current study includes 1,834 defibrillator recipients (63 ± 11 years; 79% male; 53% CRT-D). In 585 (60%) CRT-D recipients a left bundle branch block was present, the mean QRS duration was 147 ± 31 ms before and 151 ± 27 ms after device implantation. After a median follow-up of 4.4 years (25(th) -75(th) percentile 2.7-6.4 years), 285 (29%) CRT-D recipients had died. CRT-related decrease in QRS duration adjusted for QRS morphology was associated with improved survival (hazard ratio 1.05/10 ms; 95% confidence interval [CI]: 1.01-1.09; P = 0.02). The estimated 5-year survival of CRT-D recipients after implementation of the QRS characteristic was 70%, and comparable with the observed 5-year survival of 68% (95% CI: 65-72)., Conclusion: Implementation of native QRS morphology and change in QRS duration due to CRT in the SHFM improves the prognostic value of this model in HF patients with CRT-D., (©2016 Wiley Periodicals, Inc.)

Background: When triaging a patient with acute chest pain at first medical contact, an electrocardiogram (ECG) is routinely made and inspected for signs of myocardial ischemia. The guidelines recommend comparison of the acute and an earlier-made ECG, when available. No concrete recommendations for this comparison exist, neither is known how to handle J-point identification difficulties. Here we present a J-point independent method for such a comparison., Methods: After conversion to vectorcardiograms, baseline and acute ischemic ECGs after 3minutes of balloon occlusion during elective PCI were compared in 81 patients of the STAFF III ECG database. Baseline vectorcardiograms were subtracted from ischemic vectorcardiograms using either the QRS onsets or the J points as synchronization instants, yielding vector magnitude difference signals, ΔH. Output variables for the J-point synchronized differences were ΔH at the actual J point and at 20, 40, 60 and 80ms thereafter. Output variables for the onset-QRS synchronized differences were the ΔH at 80, 100, 120, 140 and 160ms after onset QRS. Finally, linear regressions of all combinations of ΔHJ+… versus ΔHQRS+… were made, and the best combination was identified., Results: The highest correlation, 0.93 (p<0.01), was found between ΔH 40ms after the J point and 160ms after the onset of the QRS complex. With a ΔH ischemia threshold of 0.05mV, 66/81 (J-point synchronized differences) and 68/81 (onset-QRS synchronized differences) subjects were above the ischemia threshold, corresponding to sensitivities of 81% and 84%, respectively., Conclusion: Our current study opens an alternative way to detect cardiac ischemia without the need for human expertise for determination of the J point by measuring the difference vector magnitude at 160ms after the onset of the QRS complex., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Progressive activation delay after premature stimulation has been associated with ventricular fibrillation in nonischemic cardiomyopathy (NICM)., Objectives: The objectives of this study were (1) to investigate prolongation of the paced QRS duration (QRSd) after premature stimulation as a marker of activation delay in NICM, (2) to assess its relation to induced ventricular arrhythmias, and (3) to analyze its underlying substrate by late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR) and endomyocardial biopsy., Methods: Patients with NICM were prospectively enrolled in the Leiden Nonischemic Cardiomyopathy Study and underwent a comprehensive evaluation including LGE-CMR, electrophysiology study, and endomyocardial biopsy. Patients without structural heart disease served as controls for electrophysiology study., Results: Forty patients with NICM were included (mean age 57 ± 14 years; 33 men [83%]; left ventricular ejection fraction 30% ± 13%). After the 400-ms drive train and progressively premature stimulation, the maximum increase in QRSd was larger in patients with NICM than in controls (35 ± 18 ms vs. 23 ± 12 ms; P = .005) and the coupling interval window with QRSd prolongation was wider (47 ± 23 ms vs. 31 ± 14 ms; P = .005). The maximum paced QRSd exceeded the ventricular effective refractory period, allowing for pacing before the offset of the QRS complex in 20 of 39 patients with NICM vs. 1 of 20 controls (P < .001). In patients with NICM, QRSd prolongation was associated with the inducibility of polymorphic ventricular tachycardia (16 of 39 patients) and was related to long, thick strands of fibrosis in biopsies, but not to focal enhancement on LGE-CMR., Conclusion: QRSd is a simple parameter used to quantify activation delay after premature stimulation, and its prolongation is associated with the inducibility of polymorphic ventricular tachycardia and with the pattern of myocardial fibrosis in biopsies., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The guidelines advocate, in patients with chest pain, comparison of the acute ECG with a previously made, non-ischemic ECG that serves as a reference, to corroborate the working diagnosis of acute coronary syndrome (ACS). Our approach of this serial comparison is to compute the differences between the ST vectors at the J point and 60 ms thereafter (∆ST(J+0), ∆ST(J+60)) and between the ventricular gradient (VG) vectors (∆VG). In the current study, we investigate if reference ECGs remain valid in time., Methods: We studied 6 elective non-ischemic ECGs (ECG0, ECG1, …, ECG5), 5 years apart, in 88 patients. Within each patient, serial comparisons were done 1) between all successive ECGs, and 2) between each of ECG1, ECG2, …, ECG5 and ECG0, computing, in addition to ∆ST(J+0), ∆ST(J+60) and ∆VG, the difference in heart rates, ∆HR. Additionally, relevant clinical events and the diagnoses associated with each ECG were collected. Linear regression was used to assess trends in ∆ST(J+0), ∆ST(J+60) and ∆VG; multiple linear regression was used to assess the influence of the clinical events and diagnoses on ∆ST(J+0), ∆ST(J+60) and ∆VG., Results: There were no trends in the differences between successive ECGs. Positive trends were seen with increasing time lapses between ECGs: ∆ST(J+0), ∆ST(J+60) and ∆VG increased per year by 0.65 μV, 1.45 μV and 3.69 mV∙ms, respectively. Extrapolation to a time lapse of 0 yielded 50.92 μV, 36.63 μV and 20.91 mV∙ms for the short-term reproducibility of ∆ST(J+0), ∆ST(J+60) and ∆VG, respectively. Multiple linear regression revealed that clinical variables could explain only 10%, 17% and 13% of the variability in ∆ST(J+0), ∆ST(J+60) and ∆VG, respectively., Conclusion: With a view on ischemia detection thresholds in the order of magnitude of 58 μV for ∆ST and 26 mV·ms for ∆VG, our study suggests that it is important to have a recent ECG available for the detection of myocardial ischemia, as an "aged" ECG may have lost its validity as a reference., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Introduction: Serial analysis could improve ECG diagnosis of myocardial ischemia caused by acute coronary occlusion., Methods: We analyzed ECG pairs of 84 cases and 398 controls. In case-patients, who underwent elective percutaneous coronary intervention, ischemic ECGs during balloon occlusion were compared with preceding non-ischemic ECGs. In control-patients, two elective non-ischemic ECGs were compared. In each ECG the ST vector at the J point and the ventricular gradient (VG) vector was computed, after which difference vectors ΔST and ΔVG were computed within patients. Finally, receiver operating characteristic analysis was done., Results: Areas under the curve were 0.906 (P<0.001; CI 0.862-0.949; SE 0.022) for ΔST and 0.880 (P<0.001; CI 0.833-0.926; SE 0.024) for ΔVG. Sensitivity and specificity of conventional ST-elevation myocardial infarction (STEMI) criteria were 70.2% and 89.1%, respectively. At matched serial analysis specificity and STEMI specificity, serial analysis sensitivity was 78.6% for ΔST and 71.4% for ΔVG (not significantly different from STEMI sensitivity). At matched serial analysis sensitivity and STEMI sensitivity, serial analysis specificity was 96.5% for ΔST and 89.3% for ΔVG; ΔST and STEMI specificities differed significantly (P<0.001)., Conclusion: Detection of acute myocardial ischemia by serial ECG analysis of ST and VG vectors has equal or even superior performance than the STEMI criteria. This concept should be further evaluated in triage ECGs of patients suspected from having acute myocardial ischemia., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Right ventricular (RV) function after ST-segment elevation myocardial infarction (STEMI) has important prognostic implications. However, the changes in RV function over time after STEMI and the incidence of RV remodeling remain unknown. The present study evaluated changes in RV dimensions and function in contemporary patients with first STEMI and assessed the independent determinants of RV dysfunction at follow-up. Patients with first STEMI (n = 940, 60 ± 11 years, 77% men) treated with primary percutaneous coronary intervention underwent echocardiography at baseline and 6- and 12-month follow-up. The prevalence of RV dysfunction (tricuspid annular plane systolic excursion [TAPSE] ≤15 mm) decreased significantly at 6 months follow-up (from 15% to 8%, p <0.001) and the incidence of RV remodeling (increase in RV end-diastolic area [RVEDA] ≥20%) was observed in 200 patients (25%). Absolute changes in RVEDA were independently associated with absolute changes in wall motion score index and left ventricular (LV) remodeling (p <0.001 for both parameters), whereas absolute changes in TAPSE were independently related with absolute changes in wall motion score index and mitral regurgitation grade (p <0.001 for both parameters). Independent correlates of RV dysfunction at 6 months follow-up were multivessel coronary disease (odds ratio [OR] 2.13), peak cardiac troponin T (OR 1.05), angiotensin-converting enzyme inhibitors and/or angiotensin receptor blockers use (OR 0.27), baseline LV ejection fraction (OR 0.96) and baseline TAPSE (OR 0.88). In conclusion, despite the non-negligible incidence of RV remodeling in patients with first STEMI, RV function improves early after STEMI. Multivessel coronary disease, infarct size, baseline LV ejection fraction and TAPSE and the nonuse of angiotensin-converting enzyme inhibitors and/or angiotensin receptor blockers are independent determinants of RV dysfunction., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: Specific 12-lead ECG criteria have been reported to predict an epicardial site of origin (SoO) of induced ventricular tachycardias (VTs) in left ventricular nonischemic cardiomyopathy., Objective: The purpose of this study was to (1) determine the value of ECG criteria to predict an epicardial SoO of clinically documented VTs, (2) analyze the effect of VT cycle length (CL) and antiarrhythmic drugs on the accuracy of ECG criteria, and (3) assess interobserver variability., Methods: In 36 consecutive patients with nonischemic left ventricular cardiomyopathy (age 58 ± 16 years, 75% male) who underwent combined endocardial/epicardial VT ablation, all clinically documented and induced right bundle branch block VTs were analyzed for previously reported ECG criteria to determine the SoO, as defined by ≥11/12 pace-map, concealed entrainment, and/or VT termination during ablation., Results: In 21 patients with clinically documented (25 mm/s) right bundle branch block VT, none of the ECG criteria differentiated between patients with and those without an epicardial SoO. In induced VTs (100 mm/s), 2 of 4 interval criteria differentiated between an endocardial and epicardial SoO for slow VTs (CL >350 ms) and 2 of 4 criteria in patients on amiodarone, but none for fast VTs (CL ≤350 ms) or patients off amiodarone. The Q wave in lead I was the most accurate criterion for an epicardial SoO (sensitivity 88%, specificity 80%). In both clinically documented and induced VTs, interobserver agreement was poor for pseudodelta wave and moderate for other criteria., Conclusion: When applied to clinically documented VTs, no ECG criterion could differentiate between patients with and those without an epicardial SoO. Published interval-based ECG criteria do not apply to fast VTs and patients off amiodarone., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Elderly patients constitute a growing part of the population presenting with ST-elevation myocardial infarction (STEMI). The use of primary percutaneous coronary intervention (PCI) in this high-risk population remains poorly investigated., Methods: Using the Swedish Coronary Angiography and Angioplasty Registry (SCAAR), we identified consecutive patients with STEMI 80 years or older undergoing primary PCI during a 10-year period. Temporal trends in care and 1-year prognosis were investigated, and long-term outcome was compared with a reference group of patients with STEMI aged 70 to 79 years. Relative survival was calculated by dividing the observed survival rate with the expected survival rate of the general population. Adjusted end points were calculated using Cox regression., Results: In total, 4,876 elderly patients with STEMI were included. During the study period, average age and presence of comorbidity increased, as well as the use of antithrombotic therapy. Procedural success remained constant. One-year mortality was exclusively reduced between the most recent vs the earliest cohort, whereas the risk of reinfarction, heart failure, stroke, and bleeding remained similar. The risk of death was higher for elderly patients early after PCI, after which the prognosis was slightly better compared with the general population. Long-term risk of adverse events increased markedly with age., Conclusions: The prognosis of patients older than 80 years treated with primary PCI for STEMI was relatively unchanged during the 10-year inclusion period, despite changes in patient characteristics and treatment. Advanced age increased the risk of adverse events, but survivors of the early phase after PCI had a slightly improved prognosis compared with the general population., (Copyright © 2014 Mosby, Inc. All rights reserved.)

Background: Biventricular (BV) electrical wavefront fusion can induce improvement in left ventricular (LV) size and function during cardiac resynchronization therapy (CRT). Changes in BV wave propagation sequence and duration register in the QRS complex on the standard electrocardiogram. We developed a wave interference method for the characterization of BV fusion to predict LV reverse remodeling., Objective: To develop a simple electrocardiographic method for predicting reverse remodeling during CRT., Methods: QRS complexes during left bundle branch block (LBBB) and CRT were analyzed in 375 patients with ejection fraction ≤35% and New York Heart Association class III-IV (Leiden study: n = 226) as well as in patients with ejection fraction ≤40% and New York Heart Association class I-II (REVERSE trial: n = 149) for predictors of ≥10% reduction in left ventricular end-systolic volume at 6 months. CRT-induced changes in ventricular activation (QRS fusion contour), electrical asynchrony (QRS difference = BV-paced QRS - LBBB QRS, in milliseconds), and LBBB substrate (LV activation time and QRS score for LV scar) were quantified., Results: Multivariable predictors of reverse remodeling were as follows: (1) either of 2 BV fusion patterns: QRS normalization in leads V1 and V2 (n = 66 [18%]; odds ratio [OR] 3.71; 95% confidence interval [CI] 1.26-10.94) or a new or an increased R wave in leads V1-V2 (n = 267 [71%]; OR 1.55; 95% CI 0.65-3.65); (2) QRS difference ≤ -25 ms (OR 2.35; 95% CI 1.12-4.91); and (3) good substrate (low to moderate QRS score and LV activation time ≥110 ms; OR 2.94; 95% CI 1.68-5.14). Remodeling rates were 40% for poor substrate and persistent LBBB QRS complex (absent BV fusion; QRS type 3: n = 42 [11%]) and 97% for the best BV QRS fusion pattern and greater reduction in electrical asynchrony (larger QRS difference)., Conclusion: Easily determined QRS complex attributes before and after CRT predict LV reverse remodeling., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: In acute coronary syndrome (ACS), ST-segment elevation (STE), often associated with a completely occluded culprit artery, is an important ECG criterion for primary percutaneous coronary intervention (PCI). However, several studies showed that in ACS a completely occluded culprit artery can also occur with a non-ST-elevation (NSTE) ECG. In order to elucidate reasons for this discrepancy we examined ST injury vector orientation and magnitude in ACS patients with and without STE, all admitted for primary PCI and having a completely occluded culprit artery., Methods: We studied the ECGs of 300 ACS patients (214/86 STE/NSTE; 228/72 single/multivessel disease) who had a completely occluded culprit artery during angiography prior to primary PCI. The J+60 injury vector orientation and magnitude were computed from Frank XYZ leads derived from the 10-s standard 12-lead ECG., Results: Demographic and anthropomorphic characteristics of the STE and NSTE patients did not differ. STE patients had a higher rate of right coronary artery occlusions, and a lower rate of left circumflex occlusions than NSTE patients (43 vs. 31%, and 13 vs. 22%, respectively; P<0.05). Injury vector elevation and magnitude were larger in STE than in NSTE patients (32° ± 37° vs. 6° ± 39°, and 304 ± 145 μV vs. 134 ± 72 μV, respectively; P<0.0001)., Conclusion: STE criteria favor certain injury vector directions and larger injury vector magnitudes. Obviously, several ACS patients with complete culprit artery occlusions requiring primary PCI do not fulfill these criteria. Our study suggests that STE-NSTE-based ACS stratification needs further enhancement., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Advances in antithrombotic therapy for ST elevation myocardial infarction (STEMI) enhance the risk of bleeding. Therefore, the incidence, determinants, and prognostic implications of in-hospital major bleeding after primary percutaneous coronary intervention for STEMI were investigated. In 963 consecutive patients, the incidence of bleeding was evaluated according to commonly used classifications including Can Rapid risk stratification of Unstable angina patients Suppress Adverse outcomes with Early implementation of the ACC/AHA guidelines, Thrombolysis In Myocardial Infarction, Global Use of Strategies To Open coronary arteries, and Bleeding Academic Research Consortium. Multivariate regression analyses investigated determinants of bleeding and the relation between bleeding and 1-year all-cause mortality. Large variability in incidence existed depending on classification (1.3% to 21%). Female gender, heart rate, creatinine, multivessel disease, cardiogenic shock, and procedural failure were independently associated with bleeding. One-year mortality reached 10.2% in bleeders versus 2.0% in nonbleeders (p <0.001). Bleeding was independently associated with an increased risk of 1-year mortality (hazard ratio [HR] 2.41, p <0.017). Assessment of individual classifications confirmed the increased risk of mortality for Bleeding Academic Research Consortium (HR 2.27, p = 0.048), but not for Can Rapid risk stratification of Unstable angina patients Suppress Adverse outcomes with Early implementation of the ACC/AHA guidelines, Thrombolysis In Myocardial Infarction, and Global Use of Strategies To Open coronary arteries bleeding. Thrombotic events occurred more frequently in bleeders (5.8% vs 1.5%, p <0.001); however, bleeding remained independently related to mortality with a negligible reduction in HR (2.25, p = 0.028) after adjustment. In conclusion, in-hospital major bleeding was frequently observed after STEMI, but a widespread variation in incidence existed depending on the applied definition. Patient and procedural characteristics were related to bleeding, allowing identification of high-risk patients. In-hospital major bleeding was independently associated with 1-year all-cause mortality; however, not all bleeding classifications proved equally relevant to prognosis. The relation between bleeding and mortality was shown not to be driven by the higher rate of thrombotic events among bleeders., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The clinical use of advanced imaging modalities for early determination of infarct size and prognosis is limited. As a specific indicator of myocardial necrosis, cardiac troponin T (cTnT) can be used as a surrogate measure for this purpose. The present study sought to investigate the use of peak and serial 6-hour fixed-time high-sensitive (hs) cTnT for estimation of infarct size, left ventricular (LV) function, and prognosis in consecutive patients with ST-segment elevation myocardial infarction. The infarct size was expressed as the 48-hour cumulative creatine kinase release. LV function at 3 months was assessed using the echocardiographic wall motion score index and LV ejection fraction using radionuclide ventriculography. Adverse outcomes, comprising all-cause death, implantable cardioverter-defibrillator implantation, or hospitalization for heart failure, were recorded at 1 year of follow-up. In 188 patients, the peak and all fixed-time values correlated significantly with the 48-hour cumulative creatine kinase release, wall motion score index, and LV ejection fraction. The hs-cTnT value at 24 hours demonstrated the greatest correlation (r = 0.86, r = 0.47, and r = -0.59, respectively; p <0.001 for all). In the multivariate regression models adjusted for the clinical parameters, almost all were independently associated with the 48-hour cumulative creatine kinase release, wall motion score index, and LV ejection fraction, with the hs-cTnT value at 24 hours having the largest effect. Moreover, all cTnT values independently predicted adverse outcomes, again, with the hs-cTnT value at 24 hours showing the largest influence (hazard ratio 3.77, 95% confidence interval 2.12 to 6.73, p <0.001). In conclusion, not only peak, but all fixed-time hs-cTnT values were associated with infarct size, LV function at 3 months, and adverse outcomes 1 year after ST-segment elevation myocardial infarction. The value 24 hours after the onset of symptoms had the closest associations with all outcomes. Therefore, serial sampling for a peak value might be redundant., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Aims: In order to improve the abysmal outcome of dialysis patients, it is critical to identify patients with a high mortality risk. The spatial QRS-T angle, which can be easily calculated from the 12 lead electrocardiogram (ECG), might be useful in the prognostication in dialysis patients. The objective of this study was to establish the prognostic value of the spatial QRS-T angle., Methods and Results: All patients who initiated dialysis therapy between 2002 and 2009 in the hospitals of Leiden (LUMC) and Amsterdam (AMC) at least 3 months on dialysis were included. The spatial QRS-T angle was calculated, from a routinely acquired ECG, and its relationship with mortality was assessed. An abnormal spatial QRS-T angle was defined as ≥ 130° in men and ≥ 116° in women. In total, 277 consecutive patients (172 male, mean age 56.3 ± 17.0) were included. An abnormal spatial QRS-T angle was associated with a higher risk of death from all causes [hazard ratio (HR) 2.33; 95% confidence interval (CI) 1.46-3.70] and especially a higher risk of sudden cardiac death (HR 2.99; 95% CI 1.04-8.60). Furthermore, an abnormal spatial QRS-T angle was of incremental prognostic value, when added to a risk model consisting of known risk factors., Conclusion: In chronic dialysis patients the spatial QRS-T angle is a significant and independent predictor of all-cause and especially sudden cardiac death. It implies that this parameter can be used to identify high risk patients.

Previous studies investigating the influence of gender on ST-segment elevation myocardial infarction have reported conflicting results. The aim of this study was to assess the influence of gender on ischemic times and outcomes after ST-segment elevation myocardial infarction in patients treated with primary percutaneous coronary intervention in modern practice. The present multicenter registry included consecutive patients with ST-segment elevation myocardial infarctions treated with primary percutaneous coronary intervention at 3 hospitals. Adjusted mortality rates were calculated using Cox proportional-hazards analyses. In total, 3,483 patients were included, of whom 868 were women (25%). Women were older, had a higher risk factor burden, and more frequently had histories of malignancy. Men more often had cardiac histories and peripheral vascular disease. Ischemic times were longer in women (median 192 minutes [interquartile range 141 to 286] vs 175 minutes [interquartile range 128 to 279] in men, p = 0.002). However, multivariate linear regression showed that this was due to age and co-morbidity. All-cause mortality was higher at 7 days (6.0% in women vs 3.0% in men, p <0.001) and at 1 year (9.9% in women vs 6.6% in men, p = 0.001). After adjustment, female gender predicted 7 day all-cause mortality (hazard ratio 1.61, 95% confidence interval 1.06 to 2.46) and cardiac mortality (hazard ratio 1.58, 95% confidence interval 1.03 to 2.42) but not 1-year mortality. Moreover, gender was an independent effect modifier for cardiogenic shock, leading to substantially worse outcomes in women. In conclusion, ischemic times remain longer in women because of age and co-morbidity. Female gender independently predicted early all-cause and cardiac mortality after primary percutaneous coronary intervention, and a strong interaction between gender and cardiogenic shock was observed., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Purpose: The aim of this study was to investigate the use of the electrocardiogram-derived ventricular gradient, projected on the x-axis (VGx), for detection of pulmonary hypertension (PH) and for prediction of all-cause mortality in PH patients., Methods: In patients referred for PH screening (n = 216), the VGx was calculated semiautomatically from the electrocardiogram and was defined as abnormal when less than 24 mV · ms. The VGx of PH patients was compared with the VGx of patients without PH. The association between a reduced VGx and mortality was investigated in PH patients., Results: Patients with PH (n = 117) had a significantly reduced VGx: 14 ± 27 vs 45 ± 23 mV · ms, P < .001. Furthermore, a severely reduced VGx (<0 mV · ms) was associated with increased mortality in PH patients: hazard ratio, 1.025 (95% confidence interval, 1.006-1.045; P = .012) per mV·ms VGx decrease., Conclusion: Reduced VGx is associated with the presence of PH and, more importantly, within PH patients, a severely reduced VGx predicts mortality., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The risk scores developed for the prediction of an adverse outcome in patients after ST-segment elevation myocardial infarction (STEMI) have mostly addressed patients treated with thrombolysis and evaluated solely all-cause mortality as the primary end point. Primary percutaneous coronary intervention in patients with STEMI has improved the outcome significantly and might have changed the relative contribution of different risk factors. Our patient population included 1,484 consecutive patients admitted with STEMI who had undergone primary percutaneous coronary intervention. The clinical, angiographic, and echocardiographic data obtained during hospitalization were used to derive a risk score for the prediction of short-term (30-day) and long-term (1- and 4-year) cardiovascular mortality and hospitalization for heart failure. During a median follow-up of 30 months, 87 patients (6%) died from cardiovascular mortality or were hospitalized for heart failure. Multivariate Cox regression analyses identified age ≥70 years, Killip class ≥2, diabetes, left anterior descending coronary artery as the culprit vessel, 3-vessel disease, peak cardiac troponin T level ≥3.5 μg/L, left ventricular ejection fraction ≤40%, and heart rate at discharge ≥70 beats/min as relevant factors for the construction of the risk score. The discriminatory power of the model as assessed using the areas under the receiver operating characteristic curves was good (0.84, 0.83, and 0.81 at 30 days and 1 and 4 years, respectively), and the patients could be allocated to low-, intermediate-, or high-risk categories with an event rate of 1%, 6%, and 24%, respectively. In conclusion, the current risk model demonstrates for the first time that 8 parameters readily available during the hospitalization of patients with STEMI treated with primary percutaneous coronary intervention can accurately stratify patients at long-term follow-up (≤4 years after the index infarction) into low-, intermediate-, and high-risk categories., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Left atrial (LA) size has been associated with adverse outcome in patients after acute myocardial infarction. However, data about the occurrence of late LA enlargement and changes in LA function during follow-up are scarce. The purpose of the current study was to evaluate changes in LA size and function during 1-year follow-up., Methods: The study population comprised 407 patients with acute myocardial infarction who were treated with primary percutaneous coronary intervention. At baseline and 12 months, two-dimensional echocardiography was performed to assess LA volumes and function using speckle-tracking strain and strain rate., Results: The mean age was 60 ± 11 years, and most patients were men (78%). LA maximal volume increased from 25 ± 8 to 28 ± 8 mL/m(2) (P < .001) from baseline to 1 year. Echocardiographic assessment at 1-year follow-up showed that 92 patients (25%) had developed LA remodeling (defined as an increase of ≥8 mL/m(2) in LA maximal volume). On multivariate analysis, only LA maximal volume at baseline (odds ratio, 0.95; 95% confidence interval, 0.91-0.98; P = .003) and LA strain at baseline (odds ratio, 0.94; 95% confidence interval, 0.92-0.97; P < .001) were independent predictors of LA remodeling during follow-up. Interestingly in patients without LA remodeling, no changes were observed in LA function during follow-up. However, in patients with LA remodeling, LA function significantly worsened during follow-up. In line, LA strain and strain rate were significantly lower at 12 months compared with baseline (24 ± 7% vs 27 ± 6%, P < .001, and 1.8 ± 0.5 vs 2.4 ± 0.7 sec(-1), P < .001, respectively)., Conclusions: LA remodeling occurred in 22% of patients after acute myocardial infarction. In patients without LA remodeling, no changes in LA function were observed, but in patients with LA remodeling, LA function deteriorated significantly.

Background: A left bundle-branch block (LBBB)-like pattern with a dominant S-wave in V(1) is common in idiopathic ventricular arrhythmias (VA). Discrimination between idiopathic and scar-related LBBB pattern VA has important clinical implications. We hypothesized that the VA QRS morphology is influenced by the presence of ventricular scar, allowing ECG discrimination of VA arising from structurally normal versus scarred myocardium., Methods and Results: Twelve-lead ECGs of 297 LBBB pattern monomorphic VA were recorded during catheter ablation procedures. QRS morphology characteristics associated with scar-related VA were identified in retrospective analysis of 118 LBBB pattern VA (95 scar-related, 23 idiopathic) to develop a stepwise algorithm that was prospectively tested in 179 LBBB pattern VA (120 scar-related, 59 idiopathic). The diagnosis of scar was based on sinus rhythm surface ECG, cardiovascular imaging, and electroanatomic catheter mapping. A precordial transition beyond V₄, notching of the S-wave downstroke in lead V₁ or V₂, and a duration from the onset of QRS to the S-nadir in V₁ >90 ms were independent predictors for scar-related VA. The proposed algorithm classified a VA as scar-related if any of these criteria was met. If none of the criteria was present, a VA was classified as idiopathic. In prospective validation, the algorithm was highly sensitive (96%) and specific (83%) for the identification of scar-related LBBB pattern VA., Conclusions: The QRS morphology of VA is different between scar-related and idiopathic VA. A simple ECG algorithm is sensitive for identifying scar-related LBBB VA, which could be helpful in guiding further evaluation of these patients.

Background and Purpose: Several studies have demonstrated that the spatial mean QRS-T angle (SA) predicts cardiac events and mortality. Spatial mean QRS-T angle is a vectorcardiographic variable. Because in clinical practice, 12-lead standard electrocardiograms (ECGs) are recorded rather than vectorcardiograms (VCGs) according to Frank, VCGs are commonly obtained by synthesizing them from 12-lead ECGs, by using a VCG synthesis matrix. Hence, the thus computed SA is an estimate of the real SA measured in the Frank VCG. Recent studies have shown that Kors VCG synthesis matrix yields better estimates of SA than the inverse Dower VCG synthesis matrix. Our current study aims to compare the predictive power of these SA variants for the occurrence of potentially lethal arrhythmias., Methods: The study group consisted of patients with ischemic heart disease and left ventricular systolic dysfunction who received an implantable cardioverter-defibrillator (ICD) for primary prevention. During follow-up, the occurrence of appropriate device therapy (occurrence of ventricular arrhythmia) was noted. Alternative SAs were computed in VCGs synthesized from standard 12-lead ECGs by using either the inverse Dower matrix (SA-Dower) or the Kors matrix (SA-Kors). Comparison of the predictive power of SA-Dower and SA- Kors was performed by receiver operating characteristic analysis, by Kaplan-Meier analysis, and by univariate and multivariate Cox regression analysis, using every 10th percentile of SA as a cutoff value., Results: The study group consisted of 412 patients (361 men; mean ± SD age 63 ± 11 years), in which 56 patients had appropriate ICD therapy during follow-up. Receiver operating characteristic analysis revealed that the area under the curve of SA-Kors was significantly larger than area under the curve of SA-Dower (0.646 vs 0.607, P = .043). The discriminative power of SA-Kors for the absence/presence of appropriate ICD therapy in patients during follow-up was generally superior to SA-Dower over a wide range of cutoff values in the Kaplan-Meier analysis and generally yielded stronger hazard ratios in the univariate and multivariate Cox regression analyses., Conclusion: If there is no specific reason to use the inverse Dower matrix, VCG synthesis from standard 12-lead ECGs should preferably be done by using the Kors matrix. It is likely to assume that already published studies in which the predictive value of SA-Dower was demonstrated would yield stronger results if the SA-Dower angles were substituted by SA-Kors angles., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Atrial fibrillation (AF) has been linked to the presence of underlying coronary artery disease (CAD). However, whether the higher burden of CAD observed in AF patients translates into higher burden of myocardial ischemia is unknown. In 87 patients (71% male, mean age 61 ± 10 years) with paroxysmal or persistent AF and without history of CAD, MSCT coronary angiography and stress testing (exercise ECG test or myocardial perfusion imaging) were performed. CAD was classified as obstructive (≥50% luminal narrowing) or not. Stress tests were classified as normal or abnormal. A population of 122 patients without history of AF, similar to the AF group as to age, gender, symptomatic status and pre-test likelihood, served as a control group. Based on MSCT, 17% of AF patients were classified as having no CAD, whereas 43% showed non-obstructive CAD and the remaining 40% had obstructive CAD. A positive stress test was observed in 49% of AF patients with obstructive CAD. Among non-AF patients, 34% were classified as having no CAD, while 41% showed non-obstructive CAD and 25% had obstructive CAD (P = 0.013 compared to AF patients). A positive stress test was observed in 48% of non-AF patients with obstructive CAD. In conclusion, the higher burden of CAD observed in AF patients is not associated to higher burden of myocardial ischemia.

Background and Purpose: Left ventricular ejection fraction lacks specificity to predict sudden cardiac death in heart failure. T-wave alternans (TWA; beat-to-beat T-wave instability, often measured during exercise) is deemed a promising noninvasive predictor of major cardiac arrhythmic event. Recently, it was demonstrated that TWA during recovery from exercise has additional predictive value. Another mechanism that potentially contributes to arrhythmogeneity is exercise-recovery hysteresis in action potential morphology distribution, which becomes apparent in the spatial ventricular gradient (SVG). In the current study, we investigated the performance of TWA amplitude (TWAA) during a complete exercise test and of exercise-recovery SVG hysteresis (SVGH) as predictors for lethal arrhythmias in a population of heart failure patients with cardioverter-defibrillators (ICDs) implanted for primary prevention., Methods: We performed a case-control study with 34 primary prevention ICD patients, wherein 17 patients (cases) and 17 patients (controls) had no ventricular arrhythmia during follow-up. We computed, in electrocardiograms recorded during exercise tests, TWAA (maximum over the complete test) and the exercise-recovery hysteresis in the SVG. Statistical analyses were done by using the Student t test, Spearman rank correlation analysis, receiver operating characteristics analysis, and Kaplan-Meier analysis. Significant level was set at 5%., Results: Both SVGH and TWAA differed significantly (P < .05) between cases (mean ± SD, SVGH: -18% ± 26%, TWAA: 80 ± 46 μV) and controls (SVGH: 5% ± 26%, TWAA: 49 ± 20 μV). Values of TWAA and SVGH showed no significant correlation in cases (r = -0.16, P = .56) and in controls (r = -0.28, P = .27). Receiver operating characteristics of SVGH (area under the curve = 0.734, P = .020) revealed that SVGH less than 14.8% discriminated cases and controls with 94.1% sensitivity and 41.2% specificity; hazard ratio was 3.34 (1.17-9.55). Receiver operating characteristics of TWA (area under the curve = 0.699, P = .048) revealed that TWAA greater than 32.5 μV discriminated cases and controls with 93.8% sensitivity and 23.5% specificity; hazard ratio was 2.07 (0.54-7.91)., Discussion and Conclusion: Spatial ventricular gradient hysteresis bears predictive potential for arrhythmias in heart failure patients with an ICD for primary prevention, whereas TWA analysis seems to have lesser predictive value in our pilot group. Spatial ventricular gradient hysteresis is relatively robust for noise, and, as it rests on different electrophysiologic properties than TWA, it may convey additional information. Hence, joint analysis of TWA and SVGH may, possibly, improve the noninvasive identification of high-risk patients. Further research, in a large group of patients, is required and currently carried out by our group., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Approximately 20% of patients with heart failure have left bundle branch block (LBBB) on surface electrocardiogram (ECG). In this group of patients, detection of right ventricular (RV) dilatation on standard ECG can be of clinical relevance because RV enlargement is an important prognostic marker. Consequently, the aim of this study was to evaluate diagnostic accuracy for several electrocardiographic criteria in determining significant RV dilatation in these patients. Standard 12-lead ECGs were obtained in 173 patients with heart failure and known LBBB. From the ECG, 3 criteria for RV dilatation were defined: presence of terminal positivity in lead aVR (late R wave in lead aVR), low voltage (<0.6 mV) in all extremity leads, and an R/S ratio <1 in lead V(5). In addition, all patients underwent comprehensive echocardiographic evaluation including assessment of RV dimensions. Measurements were performed blinded to electrocardiographic results. Significant RV dilatation was defined as an RV base-to-apex length ≥ 86 mm or an RV diastolic area ≥ 33 cm(2). Eighty-six patients (50%) had a late R wave in lead aVR, 36 patients (21%) had low voltage in extremity leads, and 67 patients (39%) had an R/S ratio <1 in lead V(5). An RV base-to-apex length ≥ 86 mm was present in 67 patients (39%), and 62 patients (36%) had an RV diastolic area ≥ 33 cm(2). Any combination of 2 to 3 positive criteria could predict an RV base-to-apex length ≥ 86 mm with a positive predictive value of 89% and a negative predictive value of 88%. Similarly, an RV diastolic area ≥ 33 cm(2) was predicted with a positive predictive value of 80% and a negative predictive value of 88%. In conclusion, combining 2 to 3 distinct electrocardiographic criteria allows for accurate detection of RV dilatation in patients with heart failure and LBBB., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background: Quantification of segmental left ventricular (LV) strain by speckle-tracking echocardiography can identify transmural infarcts in patients with chronic ischemic cardiomyopathy. The aim of the study was to explore the relationship between the LV longitudinal peak systolic strain (LPSS) of the infarct, periinfarct, and remote zones and monomorphic ventricular tachycardia (VT) inducibility on electrophysiologic (EP) study., Methods: A total of 134 patients with chronic ischemic cardiomyopathy scheduled for EP study were included. The protocol consisted of clinical, electrocardiographic, and echocardiographic evaluation, including LV longitudinal strain analysis using speckle-tracking echocardiography, immediately before EP study. An infarct segment was defined as a longitudinal strain value of greater than -5%, and a periinfarct segment was defined as immediately adjacent to an infarct segment., Results: The infarct zone had the most impaired longitudinal strain (-0.5% ± 3.0%), whereas the periinfarct and remote zones had more preserved longitudinal strain (-10.8% ± 1.9% and -14.5% ± 3.0%, respectively; analysis of variance, P < .001). Seventy-two (54%) patients had inducible monomorphic VT on EP study. There was no significant difference in LV ejection fraction (31% ± 9% vs 32% ± 11%, P = .29) between inducible and noninducible patients. Longitudinal peak systolic strain of the periinfarct zone was more impaired in inducible patients (-9.8% ± 1.5% vs -11.0% ± 2.1%, P = .001), but no differences in LPSS of the infarct (-0.5% ± 3.2% vs -0.4% ± 2.7%, P = .75) and remote (-14.6% ± 2.8% vs -14.5% ± 3.4%, P = .92) zones were observed. Only LPSS of the periinfarct zone (OR 1.43, 95% CI 1.15-1.78, P = .001) was independently related to monomorphic VT inducibility on multiple logistic regression., Conclusions: Longitudinal strain analysis may be a useful imaging tool to risk stratify ischemic patients for malignant ventricular arrhythmia., (Copyright © 2010 Mosby, Inc. All rights reserved.)

Background: Cardiac resynchronization therapy for heart failure with left bundle branch block reduces left ventricular (LV) conduction delay, contraction asynchrony, and LV end-systolic volume ("reverse remodeling"). Up to one third of patients do not improve, and the electric requirements for reverse remodeling are unclear. We hypothesized that reverse remodeling is predicted by the left bundle branch block ventricular activation sequence, the paced activation sequence, and interactions between these 2 conditions., Methods and Results: Twelve-lead ECGs during left bundle branch block and cardiac resynchronization therapy were analyzed in 202 consecutive patients (New York Heart Association class III to IV heart failure, ejection fraction < or =35%) for predictors of reverse remodeling (> or =10% reduction in end-systolic volume) at 6 months. Greater longest baseline LV activation time predicted increased odds of reverse remodeling (odds ratio [confidence interval]=1.30 [1.11, 1.52] per 10-ms increase), whereas higher QRS scores for LV scar predicted reduced reverse remodeling (odds ratio [confidence interval]=0.49 [0.27, 0.88] for each 1-point increase from 0 to 4; 0.92 [0.83, 1.01] for each 1-point increase >4). After cardiac resynchronization therapy, increasing R amplitudes in leads V(1) through V(2) (odds ratio [confidence interval]=2.76 [1.01, 7.51] for each 1x increase over [baseline Rx4.5]) and left-->right frontal axis shift (odds ratio [confidence interval]=2.00 [0.99, 4.02]), indicators of ventricular activation wavefront fusion, were positive predictors of reverse remodeling. Predicted probability of reverse remodeling ranged from <20% for patients with adverse predictors to 99% for those with positive predictors., Conclusions: Ventricular activation with the use of the ECG accurately predicts LV reverse remodeling during cardiac resynchronization therapy. Greater longest baseline LV activation time and smaller scar volume combined with wavefront fusion on the paced ECG, anticipate higher probability of reverse remodeling.

The impact of left ventricular (LV) dyssynchrony after acute myocardial infarction (AMI) on LV ejection fraction (EF) is unknown. One hundred twenty-nine patients with a first ST-elevation AMI (58 + or - 11 years, 78% men) and QRS duration <120 ms were included. All patients underwent primary percutaneous coronary intervention. Real-time 3-dimensional echocardiography and myocardial contrast echocardiography were performed to assess LV function, LV dyssynchrony, and infarct size. LV dyssynchrony was defined as the SD of the time to reach the minimum systolic volume for 16 LV segments, expressed in percent cardiac cycle (systolic dyssynchrony index [SDI]). Myocardial perfusion at myocardial contrast echocardiography was scored (1 = normal/homogenous; 2 = decreased/patchy; 3 = minimal/absent) using a 16-segment model; a myocardial perfusion index, expressing infarct size, was derived by summing segmental contrast scores and dividing by the number of segments. SDI in patients with AMI was 5.24 + or - 2.23% compared to 2.02 + or - 0.70% of controls (p <0.001). Patients with AMI and LVEF <45% had significantly higher SDI compared to patients with LVEF > or = 45% (4.29 + or - 1.44 vs 6.95 + or - 2.40, p <0.001). At multivariate analysis, SDI was independently related to LVEF; in addition, the impact of SDI on LV systolic function was incremental to infarct size and anterior location of AMI (F change 16.9, p <0.001). In conclusion, LV synchronicity is significantly impaired soon after AMI. LV dyssynchrony is related to LVEF and has an additional detrimental effect on LV function, beyond infarct size and the anterior location of AMI., (Copyright 2010 Elsevier Inc. All rights reserved.)

Background: In patients with primary prevention implantable cardioverter-defibrillators (ICDs), the incidence of life-threatening ventricular arrhythmias resulting in ICD therapy is relatively low, prompting for better risk stratification. The aim of this study was to assess the value of the QRS-T angle for prediction of ICD therapy and mortality in primary prevention patients with ischemic heart disease., Methods and Results: ICD patients (n=412, 361 men; age, 63+/-11 years) with ischemic heart disease and a left ventricular ejection fraction < or = 40% were included. After device implantation, the occurrence of appropriate ICD therapy and mortality was noted. A survival analysis was performed comparing patients with a planar QRS-T angle < or = 90 degrees (n=124, 30%) with patients with a planar QRS-T angle >90 degrees before device implantation. Furthermore, patients with a spatial QRS-T angle < or = 100 degrees (n=56, 14%) were compared with patients with a spatial QRS-T angle >100 degrees , before implantation. For patients with a planar QRS-T angle >90 degrees as compared with < or = 90 degrees , the adjusted hazard ratio for the occurrence of appropriate device therapy was 2.4 (95% CI, 1.1 to 5.2); a spatial QRS-T angle >100 degrees was associated with an adjusted hazard ratio of 7.3 (95% CI, 1.0 to 53.8). Furthermore, a spatial QRS-T angle < or = 100 degrees exhibited a positive predictive value of 98% (95% CI, 95 to 100) for the prediction of an appropriate therapy-free follow-up., Conclusions: A wide QRS-T angle is a strong predictor of appropriate device therapy in primary prevention ICD recipients with ischemic heart disease. Furthermore, a spatial QRS-T angle < or = 100 degrees might be of value in the identification of patients in whom, although currently indicated, ICD treatment should be reconsidered.

Introduction: Patients with established arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) based on task force (TF) criteria and ventricular tachycardia (VT) are at risk of VT recurrence and sudden death. Data on patients with VT due to right ventricular (RV) scar not fulfilling TF criteria are lacking. The purpose of this study was to assess the long-term arrhythmia recurrence rate and outcome in patients with scar-related right VT with and without a diagnosis of ARVC/D., Methods: Sixty-four patients (age 43.5 +/- 15 years, 49 males) presenting with nonischemic scar-related VT of RV origin were studied. Scar was identified by electroanatomical mapping, contrast echocardiography, and/or magnetic resonance imaging (MRI). Patients were evaluated and treated according to a standard institute protocol., Results: Twenty-nine (45%) patients were diagnosed with ARVC/D according to TF criteria (TF+) and 35 (55%) with RV scar of undetermined origin (TF-) at the end of follow-up (64 +/- 42 months). Patients were treated with antiarrhythmic drugs, radiofrequency catheter ablation, and/or implantable cardioverter-defibrillator (ICD) implantation. VT recurrence-free survival for TF+ and TF- was 76% versus 74% at 1 year and 45% versus 50% at 4 years (P = ns). Patients with fast index VT (cycle length [CL]< or = 250 ms, n = 31) were more likely to experience a fast VT during follow-up than patients with a slow index VT (CL > 250 ms, n = 33) (61% vs 3%, P < 0.001)., Conclusions: Scar-related RV VTs have a high recurrence rate in TF+ and TF- patients. Patients presenting with a fast index VT are at high risk for fast VT recurrence and may benefit most from ICD therapy.

Background: The potential use of the ECG for monitoring treatment effects in patients with pulmonary arterial hypertension (PAH) has not been investigated. We evaluated whether the ECG is useful for monitoring treatment response based on changes in pulmonary vascular resistance (PVR)., Methods: An ECG was recorded in 81 PAH patients at the time of diagnostic right heart catheterization and after 1 year of treatment. Patients were treated according to the guidelines. Patients were divided into two groups based on PVR (ie, < 500 or > 500 dyne x s x cm(-5)). A positive treatment response was defined as a > 25% decrease in PVR to an absolute PVR of < 500 dyne x s x cm(-5)., Results: At baseline, the 19 patients with a PVR of < 500 dyne x s x cm(-5) had a significantly lower P amplitude in lead II, a less rightward oriented QRS axis, and a more rightward T axis than the 62 patients with a PVR of > 500 dyne x s x cm(-5). Overall (n = 81), the mean (+/- SD) change in PVR was -143 +/- 360 dyne x s x cm(-5) after 1 year of treatment (p < 0.001). Twelve patients (19%) with a baseline PVR of > 500 dyne x s x cm(-5) were classified as responders. Receiver operating characteristic analysis determined that the P amplitude in lead II (area under the curve [AUC], 0.80; 95% confidence interval [CI], 0.67 to 0.94; p < 0.01), QRS axis (AUC, 0.70; 95% CI, 0.52 to 0.89; p = 0.03), and T axis (AUC, 0.90; 95% CI, 0.82 to 0.97; p < 0.001) were important determinants of treatment response. The presence of a P amplitude in lead II of < 0.175 mV and a T axis of >or= 25 degrees combined had a positive and negative predictive value for treatment response of 0.81 (95% CI, 0.37 to 0.96) and 0.94 (95% CI, 0.86 to 0.99), respectively., Conclusions: Routine ECG evaluation can be an important contribution in the assessment of treatment response in PAH patients.

Background and Purpose: Normal limits of the spatial QRS-T angle and spatial ventricular gradient (SVG) are only available from Frank vectorcardiograms (VCGs) of male subjects. We determined normal limits for these variables derived from standard 12-lead electrocardiograms (ECGs) of 660 male and female students aged 18 to 29 years., Methods: A computer algorithm was used that constructed approximated VCG leads by inverse Dower matrix transformation of the 12-lead ECG and subsequently calculated the spatial QRS-T angle, SVG magnitude, and orientation., Results: In female subjects, the QRS-T angle was more acute (females, 66 degrees +/- 23 degrees; normal, 20 degrees-116 degrees; males, 80 degrees +/- 24 degrees; normal, 30 degrees-130 degrees; P < .001), and the SVG magnitude was smaller (females, 81 +/- 23 mV x ms; normal, 39-143 mV x ms; males, 110 +/- 29 mV x ms; normal, 59-187 mV x ms; P < .001) than in male subjects. The male SVG magnitude in our study was larger than that computed in Frank VCGs (79 +/- 28 mV.ms; P < .001)., Conclusions: The spatial QRS-T angle and SVG depend strongly on sex. Furthermore, normal limits of SVG derived from Frank VCGs differ markedly from those derived from VCGs synthesized from the standard ECG. As nowadays, VCGs are usually synthesized from the 12-lead ECG; normal limits derived from the standard ECG should preferably be used.

The study aimed to assess whether the 12-lead ECG-derived ventricular gradient, a vectorial representation of ventricular action potential duration heterogeneity directed toward the area of shortest action potential duration, can improve ECG diagnosis of chronic right ventricular (RV) pressure load. ECGs from 72 pulmonary arterial hypertension patients recorded <30 days before onset of therapy were compared with ECGs from matched healthy control subjects (n = 144). Conventional ECG criteria for increased RV pressure load were compared with the ventricular gradient. In 38 patients a cardiac magnetic resonance (CMR) study had been performed within 24 h of the ECG. By multivariable analysis, combined use of conventional ECG parameters (rsr' or rsR' in V1, R/S > 1 with R > 0.5 mV in V1, and QRS axis >90 degrees ) had a sensitivity of 89% and a specificity of 93% for presence of chronic RV pressure load. However, the ventricular gradient not only had a higher diagnostic accuracy for chronic RV pressure load by receiver operating characteristic analysis [areas under the curve (AUC) = 0.993, SE 0.004 vs. AUC = 0.945, SE 0.021, P < 0.05], but also discriminated between mild-to-moderate and severe RV pressure load. CMR identified an inverse relation between the ventricular gradient and RV mass, and a trend toward a similar relation with RV volume. In conclusion, chronically increased RV pressure load is electrocardiographically reflected by an altered ventricular gradient associated with RV remodeling-related changes in ventricular action potential duration heterogeneity. The use of the ventricular gradient allows ECG detection of even mildly increased RV pressure load.

Electrocardiograms (ECGs) made with Mason-Likar electrode configuration (ML-ECGs) show well-known differences from standard 12-lead ECGs (Std-ECGs). We recorded, simultaneously, Std-ECGs and ML-ECGs in 180 subjects. Using these ECGs, 8 x 8 individual and general conversion matrices were created by linear regression, and standard ECGs were reconstructed from ML-ECGs using these matrices. The performance of the matrices was assessed by the root mean square differences between the original Std-ECGs and the reconstructed standard ECGs, by the differences in major ECG parameters, and by comparison of computer-generated diagnostic statements. As a result, we conclude that, based on the root mean square differences, reconstructions with 8 x 8 individual matrices perform significantly better than reconstructions with the group matrix and perform equally well with respect to the calculation of major electrocardiographic parameters, which gives an improved reliability of the QRS frontal axis and the maximal QRS and T amplitudes. Both types of matrices were able to reverse the underdiagnosis of inferior myocardial infarctions and the erroneous statements about the QRS frontal axis that arose in the ECGs that were made by using the Mason-Likar electrode positions.

Objectives: The purpose of this study was to evaluate the effects of cardiac resynchronization therapy (CRT) in heart failure patients with narrow QRS complex (<120 ms) and evidence of left ventricular (LV) dyssynchrony on tissue Doppler imaging (TDI)., Background: Cardiac resynchronization therapy is beneficial in selected heart failure patients with wide QRS complex (> or =120 ms). Patients with narrow QRS complex are currently not eligible for CRT, and the potential effects of CRT are not well studied., Methods: Thirty-three consecutive patients with narrow QRS complex and 33 consecutive patients with wide QRS complex (control group) were prospectively included. All patients needed to have LV dyssynchrony > or =65 ms on TDI, New York Heart Association (NYHA) functional class III/IV heart failure, and LV ejection fraction < or =35%., Results: Baseline characteristics, particularly LV dyssynchrony, were comparable between patients with narrow and wide QRS complex (110 +/- 8 ms vs. 175 +/- 22 ms; p = NS). No significant relationship was observed between baseline QRS duration and LV dyssynchrony (r = 0.21; p = NS). The improvement in clinical symptoms and LV reverse remodeling was comparable between patients with narrow and wide QRS complex (mean NYHA functional class reduction 0.9 +/- 0.6 vs. 1.1 +/- 0.6 [p = NS] and mean LV end-systolic volume reduction 39 +/- 34 ml vs. 44 +/- 46 ml [p = NS])., Conclusions: Cardiac resynchronization therapy appears to be beneficial in patients with narrow QRS complex and severe LV dyssynchrony on TDI, with similar improvement in symptoms and comparable LV reverse remodeling to patients with wide QRS complex. The current results need confirmation in larger patient cohorts.

Background: It has been shown that an implantable cardioverter defibrillator (ICD) may be beneficial when added to optimal drug treatment in patients with reduced left ventricular function who survive a myocardial infarction (MI). However, it is not known whether patients with increased risk of death after primary percutaneous coronary intervention (PCI) for ST-elevation MI also have benefit of prophylactic ICD therapy to reduce sudden cardiac death., Methods and Study Design: The DAPA trial is designed to evaluate the efficacy and safety of ICD in high-risk patients after primary PCI for ST-elevation MI. In this randomized multicenter controlled study, a total of 700 patients will be included. Enrolment started in October 2004. Inclusion criteria are thrombolysis in myocardial infarction flow less than 3 after primary PCI or left ventricular ejection fraction lower than 30% as measured short after admission for the index MI. Patients will be randomized between 30 and 60 days after their MI. The primary end point will be total death during the follow-up period of at least 3 years for each patient., Conclusions: This multicenter trial of patients at high risk of death after primary angioplasty for ST-elevation MI will evaluate prophylactic ICD therapy in addition to the current standard of care.

The ventricular gradient, a notion conceived by Wilson et al during the 1930s, has contributed considerably to a better understanding of the ECG manifestations of the cardiac repolarization process. The power of the ventricular gradient is its ability to assess the primary factors that contribute to the T wave (i.e., heterogeneity of action potential morphology throughout the ventricles) in the presence of secondary factors contributing to the T wave (i.e., heterogeneity in ventricular depolarization instants). Where T-wave morphology is an ECG expression of heterogeneity of the repolarization, the ventricular gradient discriminates between primary or secondary causes of such heterogeneity. Besides the spatial ventricular gradient (Burger's three-dimensional elaboration of Wilson's two-dimensional concept), body surface mapping of local components of the ventricular gradient has emerged as a technique for assessing local ventricular action potential duration heterogeneity. The latter is believed to contribute to localization of arrhythmogenic areas in the heart. The spatial ventricular gradient, which can be computed on the basis of a regular routine ECG and does not require body surface mapping, aims to assess the overall heterogeneity of ventricular action potential morphology. This review addresses the nature and diagnostic potential of the spatial ventricular gradient. The main focus is the role of the spatial ventricular gradient in ECG assessment of dispersion of repolarization, a key factor in arrhythmogeneity.

Electron beam computed tomographic studies have demonstrated that the extent of intracoronary calcium is related to risk of coronary events. This study was performed to gain further insight into the distribution of focal calcifications and their relation to the site of plaque rupture within the culprit artery in consecutive patients (n = 60) with acute myocardial infarction (AMI) using intravascular ultrasound imaging. Calcifications in the culprit lesion and adjacent segments were classified and counted according to their arc (< 45 degrees, 45 degrees to 90 degrees, 90 degrees to 180 degrees, > 180 degrees), length (< 1.5, 1.5 to 3.0, 3.0 to 6.0, > 6.0 mm), and dispersion (number of spots per millimeter). Calcifications at the edge of a visible rupture or ulceration were considered related to the AMI. Compared with adjacent proximal and distal segments, the culprit lesion contained more calcified spots per millimeter (0.14, 0.10, and 0.21, respectively, p < 0.05). Small calcified spots (arc < 45 degrees, length < 1.5 mm) were more common (p < 0.05). Plaque rupture or ulceration was manifest in 31 culprit lesions (52%), 14 (45%) of which contained focal calcifications. These calcified spots extended more often to 90 degrees to 180 degrees of the vessel circumference and were more often of moderate length (3 to 6 mm) compared with culprit lesions without visible plaque rupture (p < 0.05). In conclusion, culprit lesions in patients with AMI contain more and smaller calcifications compared with adjacent segments. Calcifications related to plaque rupture appear to be larger and extend over a wider arc compared with these calcified spots. Those larger calcified spots may play a role in plaque instability in a subgroup of lesions.

Introduction: Diagnosis of arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is based on a set of criteria proposed by the International Task Force (TF) for Cardiomyopathies in 1994. To fulfill these criteria, presence of both electrocardiographic and anatomical abnormalities must be assessed with ECG and imaging techniques, respectively. This may be difficult in patients with early/mild forms of the disease as detectable structural abnormalities may still be absent. We evaluated in which patients presenting with right ventricular tachycardia (VT) serial reevaluation for ARVD/C is indicated., Methods and Results: Sixty consecutive patients (41 men, mean age 40+/-15 years) were evaluated by the TF criteria for possible ARVD/C because of presentation with a left bundle branch block (LBBB) VT, representing 1 minor criterion. The presence on the ECG of a T-wave inversion beyond lead V2 (1 minor), right precordial QRS prolongation (1 major), or an epsilon wave (1 major) was assessed together with the visualization of severe regional/global right ventricle dysfunction (1 major) or mild segmental dilatation/regional hypokinesia (1 minor) by standard imaging techniques. Initially, 22 (37%) patients were diagnosed as having ARVD/C. After 47+/-39 (range 6-146) months, 23 initially TF-negative patients were reevaluated because of recurrent symptoms, with 12 (52%) additional patients now meeting the TF criteria. Eleven of these 12 (92%) patients presented initially with ECG abnormalities only, but developed structural abnormalities on imaging at follow-up., Conclusion: ECG abnormalities may precede structural abnormalities warranting serial reevaluation for ARVD/C in initially TF-negative patients presenting with LBBB VT with only ECG abnormalities.

Introduction: Repolarization heterogeneity (RH) is functionally linked to dispersion in refractoriness and to arrhythmogenicity. In the current study, we validate several proposed electrocardiogram (ECG) indices for RH: T-wave amplitude, -area, -complexity, and -symmetry ratio, QT dispersion, and the Tapex-end interval (the latter being an index of transmural dispersion of the repolarization (TDR))., Methods and Results: We used ECGSIM, a mathematical simulation model of ECG genesis in a human thorax, and varied global RH by increasing the standard deviation (SD) of the repolarization instants from 20 (default) to 70 msec in steps of 10 msec. T-wave amplitude, -area, -symmetry, and Tapex-end depended linearly on SD. T-wave amplitude increased from 275 +/- 173 to 881 +/- 456 muV, T-wave area from 34 x 10(3)+/- 21 x 10(3) to 141 x 10(3)+/- 58 x 10(3)muV msec, T-wave symmetry decreased from 1.55 +/- 0.11 to 1.06 +/- 0.23, and Tapex-end increased from 84 +/- 17 to 171 +/- 52 msec. T-wave complexity increased initially but saturated at SD = 50 msec. QT dispersion increased modestly until SD = 40 msec and more rapidly for higher values of SD. TDR increased linearly with SD. Tapex-end increased linearly with TDR, but overestimated it., Conclusion: T-wave complexity did not discriminate between differences in larger RH values. QT dispersion had low sensitivity in the transitional zone between normal and abnormal RH. In conclusion, T-wave amplitude, -area, -symmetry, and, with some limitations, Tapex-end and T-wave complexity reliably reflect changes in RH.

Background: Zones of slow conduction facilitate reentry, the major mechanism of ventricular tachycardia (VT) after myocardial infarction (MI). Identification of these zones during sinus rhythm (SR) is desirable for radiofrequency (RF) catheter ablation of VT. Local conduction velocity may correlate with electrogram duration., Objectives: The purpose of this study was to revise the definition of normal electrogram characteristics and to reevaluate the significance of low-amplitude, long-duration electrograms recorded during SR to select RF catheter ablation sites in patients with VT., Methods: Electroanatomic mapping was performed during SR in 10 control patients with normal left ventricles (LVs) and in 10 patients with stable VT after MI. From the controls, reference values for electrogram amplitude, duration (first peak to last peak distance), and fragmentation (positive deflection) were derived. In patients after MI, areas with signals exceeding these values were annotated and related to successful ablation sites., Results: Ninety-five percent of normal LV electrograms were > or =1.0 mV and < or =28 ms (range 5-39 ms) and all had < or =4 deflections. Based on these results, cutoff values were set at 1 mV, four deflections, and 40 ms. In infarcted hearts, 653 electrograms (44%) were <1.0 mV and of these, 303 were > or =40 ms with >4 deflections and restricted to circumscribed areas. Twenty-seven of 28 targeted VTs remained noninducible after RF catheter ablation within these areas, resulting in 86% sensitivity and 94% specificity for low-amplitude, long-duration electrograms predicting successful ablation sites., Conclusion: Identification of successful RF target areas during SR in patients with VT is feasible with high sensitivity and specificity using a mapping strategy based on voltage and duration criteria.

Cardiac resynchronization therapy (CRT) is considered a major advance in the treatment of patients with heart failure. The presence of left ventricular (LV) dyssynchrony seems mandatory for a positive response to CRT. Currently, only patients with wide QRS complexes are considered for CRT, although patients with narrow QRS complexes may also have LV dyssynchrony. In the present study, the incidence of LV dyssynchrony was prospectively evaluated in 64 patients with heart failure and narrow QRS complexes using tissue Doppler imaging.

Several electrocardiographic indices for repolarization heterogeneity have been proposed previously. The behavior of these indices under two different stressors at the same heart rate (i.e., normotensive gravitational stress, and hypertensive isometric stress) was studied. ECG and blood pressure were recorded in 56 healthy men during rest (sitting with horizontal legs), hypertensive stress (performing handgrip), and normotensive stress (sitting with lowered legs). During both stressors, heart rates differed <10% in 41 subjects, who constituted the final study group. Heart rate increased from 63 +/- 9 beats/min at rest to 71 +/- 11 beats/min during normotensive, and to 71 +/- 10 beats/min during hypertensive stress (P < 0.001). Systolic blood pressure was 122 +/- 15 mmHg at rest and 121 +/- 15 mmHg during normotensive stress, and increased to 151 +/- 17 mmHg during hypertensive stress (P < 0.001). The QT interval was larger during hypertensive (405 +/- 27) than during normotensive stress (389 +/- 26, P < 0.001). QT dispersion did not differ significantly between the two stressors. The mean interval between the apex and the end of the T wave (Tapex-Tend) of the mid-precordial leads was larger during hypertensive (121 +/- 17 ms) than during normotensive stress (116 +/- 15 ms, P < 0.001). The singular value decomposition T wave index was larger during hypertensive (0.144 +/- 0.071) than during normotensive stress (0.089 +/- 0.053, P < 0.001). Most indices of repolarization heterogeneity were larger during hypertensive stress than during normotensive stress. Hypertensive stressors are associated with arrhythmogeneity in vulnerable hearts. This may in part be explained by the induction of repolarization heterogeneity by hypertensive stress.