Search

Catheter navigation and 3-dimensional (3D) cardiac mapping are essential components of minimally invasive electrophysiological procedures.The purpose of this study was to develop a novel 3D mapping system (KODEX - EPD, EPD Solutions, Best, The Netherlands) that measures changing electric field gradients induced on intracardiac electrodes to enable catheter localization and real-time 3D cardiac mapping.We first validated the accuracy of the system's measurement and localization capabilities by comparing known and KODEX - EPD-measured distances and locations at 12 anatomical landmarks in both the atria and ventricles of 4 swine. Next, in vivo images of 3D porcine cardiac anatomy generated by KODEX - EPD and widely used CARTO 3 system (Biosense Webster, Inc., Diamond Bar, CA) were compared with gold standard computed tomography images acquired from the same animals. Finally, 3D maps of atrial anatomy were created for 22 patients with paroxysmal atrial fibrillation (Dielectric Unravelling of Radiofrequency ABLation Effectiveness trial).First, the mean error between known and measured distances was 1.08 ± 0.11 mm (P.01) and the overall standard deviation between known and measured locations in 12 areas of the porcine heart was 0.35 mm (P.01). Second, an expert comparison of 3D image quality revealed that KODEX - EPD is noninferior to CARTO 3. Third, the system enabled 3D imaging of atrial anatomy in humans, provided real-time images of atrioventricular valves, and detected important anatomical variations in a subset of patients.The KODEX - EPD system is a novel 3D mapping system that accurately detects catheter location and can generate high-resolution images without the need for preacquired imaging, specialty catheters, or a point-by-point mapping procedure.

BACKGROUND: The postpacing interval (PPI) minus the tachycardia cycle length (TCL) is frequently used to investigate tachycardias. However, a variety of issues (eg, failure to entrain, decremental conduction, and oscillating TCLs) can make interpretation of the PPI–TCL challenging. OBJECTIVE: The purpose of this study was to investigate a novel maneuver to confirm the PPI–TCL value without using either the ventricular PPI or the TCL interval and to assess the ability of this maneuver to identify decremental conduction and differentiate supraventricular tachycardias. METHODS: We analyzed 77 intracardiac recordings from patients (age 25 ± 20 years; 40 female) who underwent catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) or orthodromic reciprocating tachycardia (ORT) with a concealed pathway. We calculated the PPI–TCL, the AH-corrected PPI–TCL, and estimated the PPI–TCL using “dual-chamber entrainment” calculated as [PPI(V) − TCL = Stim(A→V) + Stim(V→A) − PPI(A)]. RESULTS: The PPI–TCL calculated by dual-chamber entrainment highly correlated with the observed and AH-corrected PPI–TCL (R(2) = 0.79 and 0.96, respectively; P 10 ms) decrement. CONCLUSION: Dual-chamber entrainment estimates the PPI–TCL value without using either the ventricular PPI or the TCL interval. This maneuver adjusts for all decremental conduction, including within concealed pathways, where a dual-chamber entrainment PPI–TCL value >80 ms favors AVNRT over ORT. This maneuver can be used to verify the observed PPI–TCL value in challenging cases.

Undersensing of premature ventricular beats and low-amplitude R waves are primary causes for inappropriate bradycardia and pause detections in insertable cardiac monitors (ICMs).The purpose of this study was to develop and validate an enhanced algorithm to reduce inappropriately detected bradycardia and pause episodes.Independent data sets to develop and validate the enhanced algorithm were derived from a database of ICM-detected bradycardia and pause episodes in de-identified patients monitored for unexplained syncope. The original algorithm uses an auto-adjusting sensitivity threshold for R-wave sensing to detect tachycardia and avoid T-wave oversensing. In the enhanced algorithm, a second sensing threshold is used with a long blanking and fixed lower sensitivity threshold, looking for evidence of undersensed signals. Data reported includes percent change in appropriate and inappropriate bradycardia and pause detections as well as changes in episode detection sensitivity and positive predictive value with the enhanced algorithm.The validation data set, from 663 consecutive patients, consisted of 4904 (161 patients) bradycardia and 2582 (133 patients) pause episodes, of which 2976 (61%) and 996 (39%) were appropriately detected bradycardia and pause episodes. The enhanced algorithm reduced inappropriate bradycardia and pause episodes by 95% and 47%, respectively, with 1.7% and 0.6% reduction in appropriate episodes, respectively. The average episode positive predictive value improved by 62% (P.001) for bradycardia detection and by 26% (P.001) for pause detection, with an average relative sensitivity of 95% (P.001) and 99% (P = .5), respectively.The enhanced dual sense algorithm for bradycardia and pause detection in ICMs substantially reduced inappropriate episode detection with a minimal reduction in true episode detection.

We recently reported that subcutaneous nerve activity (SCNA) can be used to estimate sympathetic tone.The purpose of this study was to test the hypothesis that left thoracic SCNA is more accurate than heart rate variability (HRV) in estimating cardiac sympathetic tone in ambulatory dogs with myocardial infarction (MI).We used an implanted radiotransmitter to study left stellate ganglion nerve activity (SGNA), vagal nerve activity (VNA), and thoracic SCNA in 9 dogs at baseline and up to 8 weeks after MI. HRV was determined based on time-domain, frequency-domain, and nonlinear analyses.The correlation coefficients between integrated SGNA and SCNA averaged 0.74 (95% confidence interval [CI] 0.41-1.06) at baseline and 0.82 (95% CI, 0.63-1.01) after MI (P.05 for both). The absolute values of the correlation coefficients were significantly larger than that between SGNA and HRV analysis based on time-domain, frequency-domain, and nonlinear analyses, respectively, at baseline (P.05 for all) and after MI (P.05 for all). There was a clear increment of SGNA and SCNA at 2, 4, 6, and 8 weeks after MI, whereas HRV parameters showed no significant changes. Significant circadian variations were noted in SCNA, SGNA, and all HRV parameters at baseline and after MI, respectively. Atrial tachycardia (AT) episodes were invariably preceded by SCNA and SGNA, which were progressively increased from 120th, 90th, 60th, to 30th seconds before AT onset. No such changes of HRV parameters were observed before AT onset.SCNA is more accurate than HRV in estimating cardiac sympathetic tone in ambulatory dogs with MI.

Background The Tpeak to Tend (Tpe) interval on the 12-lead electrocardiogram predicts an increased risk of sudden cardiac arrest (SCA). There is controversy over whether Tpe would be more useful if corrected for heart rate (Tpec). Objectives We evaluated whether the predictive value of Tpe for SCA improves with heart rate correction and sought to determine an optimal cutoff value for Tpec in the context of SCA risk. Methods Cases of SCA (n = 628; mean age 66.4 ± 14.5 years; n=416, 66.2% men) from the Oregon Sudden Unexpected Death Study with an archived electrocardiogram available prior and unrelated to the SCA event were analyzed. Comparisons were made with control subjects (n = 819; mean age 66.7 ± 11.5 years; n=559, 68.2% men). The Tpe interval was corrected for heart rate using Bazett (TpecBa) and Fridericia (TpecFd) formulas, and the predictive value of Tpec for SCA was evaluated using logistic regression models. Results The area under the curve for Tpec predicting SCA improved with both correction formulas. TpecBa and TpecFd were shown to have an area under the curve of 0.695 and 0.672, respectively, as compared with a baseline of 0.601 with an uncorrected Tpe. A TpecBa value of >90 ms was predictive of SCA, independent of age, sex, comorbidities, QRS duration, corrected QT interval, and severely reduced left ventricular ejection fraction (≤35%; odds ratio 2.8; 95% confidence interval 1.92–4.17; P Conclusion Correcting Tpe for heart rate, using either the Bazett or the Fridericia formula, improved the independent predictive value of this marker for the assessment of SCA risk. Prolongation of TpecBa beyond 90 ms was associated with a nearly 3-fold increased risk of SCA.

Background Rhythmia is a new technology capable of rapid and high-resolution mapping. However, its potential advantage over existing technologies in mapping complex scar-related atrial tachycardias (ATs) has not yet been evaluated. Objective The purpose of this study was to examine the utility of Rhythmia for mapping scar-related ATs in patients who had failed previous ablation procedure(s). Methods This multicenter study included 20 patients with recurrent ATs within 2 years after a previous ablation procedure (1.8 ± 0.7 per patient). In all cases, the ATs could not be adequately mapped during the index procedure because of scar with fractionated electrograms, precluding accurate time annotation, frequent change in the tachycardia in response to pacing, and/or degeneration into atrial fibrillation. These patients underwent repeat mapping and ablation procedure with Rhythmia. Results From a total of 28 inducible ATs, 24 were successfully mapped. Eighteen ATs (75%) terminated during radiofrequency ablation and 4 (16.6%) with catheter pressure or entrainment from the site of origin or isthmus. Two ATs that were mapped to the interatrial septum slowed but did not terminate with ablation. In 21 of 24 ATs the mechanism was macroreentry, while in 3 of 24 the mechanism was focal. Interestingly, in 5 patients with previously failed ablation of an allegedly "focal" tachycardia, high-resolution mapping demonstrated macroreentrant arrhythmia. The mean mapping time was 28.6 ± 17 minutes, and the mean radiofrequency ablation time to arrhythmia termination was 3.2 ± 2.6 minutes. During a mean follow-up of 7.5 ± 3.1 months, 15 of 20 patients (75%) were free of AT recurrences. Conclusion The Rhythmia mapping system may be advantageous for mapping complex scar-related ATs.

BACKGROUND: Long QT syndrome (LQTS) is characterized by reduced penetrance and variable QT prolongation over time, resulting in an estimate of 25% carriers of a pathogenic mutation with a normal corrected QT (QTc) interval on the resting electrocardiogram (ECG). OBJECTIVE: The purpose of this study was to test the hypothesis that an individualized corrected QT interval derived from 24-hour Holter data more accurately predicts carriage of a pathogenic LQTS mutation than did QT derived from a standard 12-lead ECG and corrected using the Bazett formula (QTc interval). METHODS: Carriers of a pathogenic LQTS mutation and their genotype-negative family members who had both resting ECG and Holter recordings available were included. Automated and manual measurements of QTc were performed. QTi was derived from 24-hour Holter recordings and defined as the QT value at the intersection of an RR interval of 1000 ms, with the linear regression line fitted through QT-RR data points of each individual patient. RESULTS: In total, 69 patients with LQTS (23 long QT type 1, 39 long QT type 2, and 7 long QT type 3) and 55 controls were selected. Demographic characteristics were comparable. A comparison of the receiver operating characteristic curves indicates that the test added diagnostic value compared to manual measurement (P = .02) or automated measurement (P = .005). The diagnostic accuracy of manually measured QTc using conventional cutoff criteria was 72%, while it was 92% using a sex-independent QTi cutoff of 445 ms. This was caused by a 39% increase in sensitivity without compromising the specificity. CONCLUSION: QTi derived from Holter recordings is superior to conventional QTc measured from a standard 12-lead ECG in predicting the mutation carrier state in families with LQTS

Background The failure to identify a successful target site for catheter ablation despite extensive endocardial and epicardial mapping is a common feature for an intramural site of origin of a ventricular arrhythmia. Objective The purpose of this study was to assess whether transient suppression of premature ventricular complexes (PVCs) by injection of cold saline into the distal coronary venous system can identify an intramural focus. Methods Cold saline (room temperature) was injected through an irrigated-tip catheter into the distal coronary venous system in a consecutive series of 26 patients with frequent PVCs referred for catheter ablation. Results PVCs were temporarily suppressed in 11 of 26 patients during injection of cold saline. Extensive mapping suggested the presence of an intramural site of origin in 9 of 11 patients with PVC suppression by cold saline but in only 1 of 15 patients in whom PVCs were not suppressed. The suppression of PVCs by cold saline was associated with the presence of an intramural PVC focus with an accuracy of 88% (sensitivity 90%, specificity 88%, positive predictive value 82%, negative predictive value 93%, P = .0002). Conclusion Temporary suppression of PVCs by cold saline infused into the distal coronary venous system and the perforator veins strongly suggests the presence of an intramural septal focus of the PVCs.

Numerous electrocardiographic (ECG) criteria have been proposed to identify localization of outflow tract ventricular arrhythmias (OT-VAs); however, in some cases, it is difficult to accurately localize the origin of OT-VA using the surface ECG.The purpose of this study was to assess a simple criterion for localization of OT-VAs during electrophysiology study.We measured the interval from the onset of the earliest QRS complex of premature ventricular contractions (PVCs) to the distal right ventricular apical signal (the QRS-RVA interval) in 66 patients (31 men aged 53.3 ± 14.0 years; right ventricular outflow tract [RVOT] origin in 37) referred for ablation of symptomatic outflow tract PVCs. We prospectively validated this criterion in 39 patients (22 men aged 52 ± 15 years; RVOT origin in 19).Compared with patients with RVOT PVCs, the QRS-RVA interval was significantly longer in patients with left ventricular outflow tract (LVOT) PVCs (70 ± 14 vs 33.4±10 ms, P.001). Receiver operating characteristic analysis showed that a QRS-RVA interval ≥49 ms had sensitivity, specificity, and positive and negative predictive values of 100%, 94.6%, 93.5%, and 100%, respectively, for prediction of an LVOT origin. The same analysis in the validation cohort showed sensitivity, specificity, and positive and negative predictive values of 94.7%, 95%, 95%, and 94.7%, respectively. When these data were combined, a QRS-RVA interval ≥49 ms had sensitivity, specificity, and positive and negative predictive values of 98%, 94.6%, 94.1%, and 98.1%, respectively, for prediction of an LVOT origin.A QRS-RVA interval ≥49 ms suggests an LVOT origin. The QRS-RVA interval is a simple and accurate criterion for differentiating the origin of outflow tract arrhythmia during electrophysiology study; however, the accuracy of this criterion in identifying OT-VA from the right coronary cusp is limited.

Atrial fibrosis plays an important role in the genesis and perpetuation of atrial arrhythmias including atrial fibrillation. It promotes arrhythmias by several mechanisms including abnormal automaticity, triggered ectopic activity, and conduction slowing predisposing to reentry. Detection of atrial fibrosis by imaging modalities is desirable, but clinically challenging. Cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement has been extensively studied for this purpose. While it can detect scar in the relatively thicker ventricular myocardium, the current CMR technology is suboptimal for the detection of scar in thin wall atria, resulting in significant center-to-center variability and nonreproducibility. Major shortcomings include limited spatial resolution for the detection of tissue fibrosis, cardiac rhythm, and contractile motion as well as respiratory-induced motion resulting in blurring, and high signal of neighboring blood that makes it difficult to distinguish scar from blood, resulting in inherent volumetric errors. In a previous issue of HeartRhythm, Ling et al 1 examined the utility of contrast-enhanced multidetector computed tomography (CE-MDCT) for the detection of atrial scar. In 20 patients undergoing repeat left atrial ablation for atrial fibrillation, a preprocedural CE-MDCT was performed and an image attenuation index was compared to endocardial bipolar voltage amplitude obtained during electroanatomic mapping. The authors reported a linear correlation between atrial myocardial image attenuation on CE-MDCT and bipolar voltage amplitude in the left atrium, suggesting a new tool to assess atrial fibrosis. While these findings are novel, significant concerns about the study design, methodology, findings, and clinical implications warrant discussion.