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Background Until now, there is no consensus regarding the definition of a clinical response to cardiac resynchronization therapy ( CRT) in patients with chronic heart failure ( CHF) and systolic left ventricular ( LV) dysfunction. The aim of this study was to evaluate if echocardiography is predictive for an objective improvement in exercise capacity during long-term follow-up of CRT. Methods Each patient underwent echocardiography and spiroergometry both at baseline and at last follow-up. Left ventricular dyssynchrony ( LVD) before CRT was defined by tissue Doppler imaging ( TDI) as intra- LV delay ≥40 msec (septal-lateral or anterior-posterior). Clinical response to CRT was defined as increase of peak VO2 or as increase of maximal workload >10% as compared to baseline. Results Mean follow-up was 69 ± 37 months. From the 238 consecutive patients included in the study, 141 (59%) were classified as clinical responders and 97 (41%) as nonresponders. Baseline data of responders and nonresponders were comparable. However, clinical responders showed more often LVD (64%) than nonresponders (42%, P = 0.004). On multivariate regression analysis, nonischemic origin of CHF (β-coefficient in the final model 0.1, P = 0.04) and LVD at baseline (β-coefficient in the final model 0.2, P < 0.001) were independently associated with clinical response during long-term follow-up. Patients with LVD at baseline had significant more often an improvement of left ventricular ejection fraction >10% (P = 0.02) and a reduction of left ventricular end-diastolic diameter ( LVEDD) >10% (P < 0.01) than patients without LVD at baseline. Conclusions LVD at baseline as assessed by a straightforward echocardiographic approach predicts the long-term clinical response to CRT and is associated with a more pronounced reverse LV remodeling. [ABSTRACT FROM AUTHOR]

Background. Ventricular dyssynchrony is an co-determinant of progression and exacerbation of heart failure (HF). The co-existence of ventricular dyssynchrony with hypertension (HT) and HF were shown, however there is no data regarding the effect of circadian rhythm of blood pressure (BP) on ventricular synchrony. Therefore, we aimed to study the left ventricular synchrony in dipper and non-dipper normotensive and hypertensive participants. Methods. Participants ( n = 142) were categorized into four groups as 'Normotensive-Dipper' (NT-D) ( n = 40), 'Normotensive-Non-dipper' (NT-ND) ( n = 30), 'Hypertensive-Dipper' (HT-D) ( n = 38) and 'Hypertensive-Non-dipper' (HT-ND) ( n = 34). Left ventricular dyssynchrony was investigated by color-coded tissue Doppler imaging. Results. Non-dippers had higher 24-h and night-time BP both in normotensives and hypertensives. The incidence of ventricular dyssynchrony (a Ts-SD-12 > 34.4 ms) was higher in the hypertensive group (47.2% vs 24.3%, p = 0.005). The frequency of ventricular dyssynchrony was higher in the HT-ND group than the HT-D group (58.8% vs 36.8%, p = 0.05); however, the frequency of ventricular dyssynchrony was similar among the normotensives (26.7% vs 22.5%, p = 0.45). Ts-SD-12 and Ts-12 were higher in NT-ND group than the NT-D group. Conclusions. Non-dipping BP pattern was associated with impaired left ventricular contraction synchrony in both normotensive and hypertensive participants, which may be related with short- and long-term effects of HT on myocardium. [ABSTRACT FROM AUTHOR]

Background Sickle cell anemia ( SCA) is the most common inherited anemia. Although heart involvement in SCA is well-established, there is no data about changes of contraction synchrony in SCA. Therefore, we aimed to study the left ventricular contraction synchrony in SCA patients with narrow QRS and normal ejection fraction ( EF). Methods Thirty-six patients with SCA and 37 age- and gender-matched control subjects were included in the study. Left ventricular dyssynchrony was investigated by color-coded tissue Doppler imaging. Results The SCA patients had lower hemoglobin (Hb) and higher ferritin, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, left ventricular mass index ( LVMI), and pulmonary artery pressure. Peak A velocity, Dt, and E/E′ values were higher in the SCA group however, E/A ratio and average Em were higher in the control group. LV systolic dyssynchrony parameters including Ts- SD-12, Ts-12, Ts- SD-6, and Ts-6 were found to be higher in SCA group when compared with controls. In addition to that, the patients with ventricular dyssynchrony (a Ts- SD-12 > 34.4 msec) were higher in the SCA group than the control group (55.6% vs. 8.1%, P < 0.001). In the correlation analysis, systolic dyssynchrony parameters were found to be correlated with Hb, ferritin, LVMI, E/A, Dt, Em. Conclusion Our results revealed that in SCA patients with normal EF and narrow QRS, left ventricular systolic dyssynchrony was an early manifestation of heart involvement and might be coexisted with or preceding diastolic dysfunction. [ABSTRACT FROM AUTHOR]

Objectives: The aim of our study was to evaluate the relationship between left ventricular (LV) dyssynchrony and the risk of ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients enrolled in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial—Cardiac Resynchronization Therapy) trial. Background: Intraventricular mechanical dyssynchrony might be an important factor in ventricular arrhythmogenesis by enhancing electrical heterogeneity in heart failure patients. The effects of dyssynchrony have not yet been evaluated in a large cohort of implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy with defibrillator (CRT-D) patients. Methods: LV dyssynchrony was measured at baseline and at 12-months by speckle-tracking echocardiography, defined as the standard deviation of time to peak systolic strain in 12 LV myocardial segments. The endpoint was the first VT/VF/death or VT/VF. LV dyssynchrony was evaluated in 764 left bundle branch block (LBBB) patients and in 312 non-LBBB patients. Results: Baseline LV dyssynchrony was not predictive of VT/VF/death or VT/VF in LBBB or non-LBBB patients in either treatment arm. In CRT-D patients with LBBB, improvement in LV dyssynchrony over a year was associated with significantly lower incidence of VT/VF/death (p < 0.001) and VT/VF (p < 0.001) compared to ICD patients and to CRT-D patients with unchanged or worsening dyssynchrony. Among LBBB patients, 15% decrease in LV dyssynchrony was associated with lower risk of VT/VF/death (hazard ratio: 0.49, 95% confidence interval: 0.24 to 0.99, p = 0.049) and VT/VF (hazard ratio: 0.30, 95% confidence interval: 0.12 to 0.77, p = 0.009) as compared to ICD patients. Patients without LBBB receiving CRT-D did not show reduction in VT/VF/death or in VT/VF in relation to improving dyssynchrony when evaluating cumulative event rates or risk of events. Conclusions: Baseline LV dyssynchrony did not predict VT/VF/death or VT/VF in mild heart failure patients with or without LBBB. CRT-induced improvement of LV dyssynchrony was associated with significant reduction of ventricular arrhythmias in patients with LBBB. (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy [MADIT-CRT]; NCT00180271) [Copyright &y& Elsevier]

Aims Right ventricular apical pacing (RVAP) may be deleterious, determining abnormal left ventricular (LV) electrical activation and progressive LV dysfunction. Permanent His-bundle pacing (HBP) has been proposed to prevent this detrimental effect. The aim of our study was to compare the long-term effects of HBP on LV synchrony and systolic performance with those of RVAP in the same group of patients. Methods Our analysis included 26 patients who received both an HBP lead and an RVAP lead, as backup, in our electrophysiology laboratory between 2004 and 2007. After implantation, all devices were programmed to obtain HBP. An intra-patient comparison of the effects of HBP and RVAP on LV dyssynchrony and function was performed at the last available follow-up examination. Results After a mean of 34.6 ± 11 months, the pacing modality was temporarily switched to RVAP. During RVAP, LV ejection fraction significantly decreased (50.1 ± 8.8% vs. 57.3 ± 8.5%, P < 0.001), mitral regurgitation significantly increased (22.5 ± 10.9% vs.16.3 ± 12.4%; P = 0.018), and inter-ventricular delay significantly worsened (33.4 ± 19.5 ms vs. 7.1 ± 4.7 ms, P = 0.003) in comparison with HBP. However, the myocardial performance index was not statistically different between the two pacing modalities (P = 0.779). No asynchrony was revealed by tissue Doppler imaging during HBP, while during RVAP the asynchrony index was significantly higher in both the four-chamber (125.8 ± 63.9 ms; P = 0.035 vs. HBP) and two-chamber (126 ± 86.5 ms; P = 0.037 vs. HBP) apical views. Conclusion His-bundle pacing has long-term positive effects on inter- and intra-ventricular synchrony and ventricular contractile performance in comparison with RVAP. It prevents asynchronous pacing-induced LV ejection fraction depression and mitral regurgitation. [ABSTRACT FROM PUBLISHER]

Objectives The objective of this study is to ascertain the effects of the left (LV) and right (RV) ventricular lead tip position in response to cardiac resynchronization therapy (CRT). Background The REVERSE randomized trial examined the effects of CRT in patients with asymptomatic or mildly symptomatic heart failure (HF). Methods We analysed data collected from the active group (CRT-ON) of REVERSE in whom the precise locations of the LV and RV ventricular lead tips were determined from postoperative chest roentgenograms as part of a prespecified sub-study. LV position was classified as lateral or non-lateral, and apical or non-apical. RV position was classified as apical or non-apical. Echocardiographic LV end-systolic volume index (LVESVi), QRS duration, and clinical outcomes at 12–24 months of follow-up were evaluated with respect to the lead tip position. The primary trial endpoint was the proportion of patients with a worsened HF clinical composite response, scored as improved, unchanged, or worsened. Results Totally 346 patients included in this analysis were followed for a median of 12.6 months (interquartile range: 11.9–23.9 months). The proportion of worsened HF clinical composite response did not correlate with lead position, whereas a significantly greater decrease in the powered secondary endpoint of LVESVi was observed with the non-apical vs. the apical LV lead positions. CRT-paced QRS duration was significantly shorter than at baseline in patients with lateral vs. non-lateral LV position, as well non-apical vs. apical LV position. The incidence of composite endpoint of death and first hospitalization for HF was lower in the LV lateral than in the non-lateral (HR 0.44; 95% CI 0.19–0.99; P= 0.04), and in the LV non-apical than in the apical group (HR 0.27; 95% CI 0.11–0.63; P= 0.001). No significant differences were observed between RV apical and non-apical positions of the lead tip. Conclusions A more favourable outcome of CRT with regard to LV reverse remodelling and the composite of time to death or first HF hospitalization was observed when the LV lead tip was implanted in the lateral wall, away from the apex, while the position of the RV lead tip was indifferent. The long-term change in QRS duration was significantly associated with the position of the LV lead tip. [ABSTRACT FROM PUBLISHER]

Background: Ventricular dyssynchrony is a common finding in patients with heart failure (HF), especially in the presence of conduction delays. The loss of ventricular synchrony leads to progressive impairment of contractile function, which may be explained in part by segmental abnormalities of myocardial metabolism. However, the association of these metabolic disarrangements with parameters of ventricular dyssynchrony and electrocardiography (ECG) findings has not yet been studied. Methods: Our aim was to determine the correlation between the presence of left bundle branch block (LBBB) with left ventricular (LV) mechanical synchrony assessed by multiple-gated acquisition scan (MUGA) and with patterns of 18-fluorodeoxyglucose (18FDG) uptake in patients with non-ischemic heart failure. Twenty-two patients with non-ischemic cardiomyopathy, LV ejection fraction (LVEF) ≤45% and New York Heart Association (NYHA) Functional Class II or III symptoms under standard medical therapy were included, along with 10 healthy controls matched for age and gender. A 12-lead ECG was obtained to measure the length of the QRS. Mechanical LV synchrony was assessed by MUGA using phase analysis. All patients and controls underwent positron emission tomography with 18FDG to determine the distribution of myocardial glucose uptake. The standard deviation of peak 18FDG uptake was used as an index of metabolic heterogeneity. Student''s t-test and Pearson''s correlation were used for statistical analysis. Results: The mean age of the patients with HF was 54 ± 12 years and 72% were male. The length of the QRS was 129 ± 31 milliseconds and LBBB was present in 9 patients. Patients with HF had decreased LV 18FDG uptake compared with controls (7.56 ± 3.36 vs 11.63 ± 4.55 standard uptake value; p = 0.03). The length of the QRS interval correlated significantly with glucose uptake heterogeneity (r = 0.62; p = 0.002) and mechanical dyssynchrony (r = 0.63; p = 0.006). HF patients with LBBB showed marked glucose uptake heterogeneity compared with HF patients without LBBB (41.4 ± 10 vs 34.7 ± 4.9 ml/100 g/min, respectively; p = 0.01). Conclusions: Patients with non-ischemic heart failure exhibit a global decrease in myocardial glucose uptake. Within this group, subjects who also have LBBB exhibit a marked heterogeneity in segmental glucose uptake, which directly correlates with QRS duration. [Copyright &y& Elsevier]

Background: The controversial effects promoted by cardiac resynchronization therapy (CRT) on the ventricular repolarization (VR) have motivated VR evaluation by body surface potential mapping (BSPM) in CRT patients. Methods: Fifty-two CRT patients, mean age 58.8 ± 12.3 years, 31 male, LVEF 27.5 ± 9.2, NYHA III-IV heart failure with QRS181.5 ± 14.2 ms, underwent 87-lead BSPM in sinus rhythm (BASELINE) and biventricular pacing (BIV). Measurements of mean and corrected QT intervals and dispersion, mean and corrected T peak end intervals and their dispersion, and JT intervals characterized global and regional (RV, Intermediate, and LV regions) ventricular repolarization response. Results: Global QTm (P < 0.001) and QTcm (P < 0.05) were decreased in BIV; QTm was similar across regions in both modes (P = ns); QTcm values were lower in RV/LV than in Intermediate region in BASELINE and BIV (P < 0.001); only RV/Septum showed a significant difference (P < 0.01) in the BIV mode. QTD values both of BASELINE (P < 0.01) and BIV (P < 0.001) were greater in the Intermediate than in the LV region. CRT effect significantly reduced global/regional QTm and QTcm values. QTD was globally decreased in RV/LV (Intermediate: P = ns). BIV mode significantly reduced global T peak end mean and corrected intervals and their dispersion. JT values were not significant. Conclusions: Ventricular repolarization parameters QTm, QTcm, and QTD global/regional values, as assessed by BSPM, were reduced in patients under CRT with severe HF and LBBB. Greater recovery impairment in the Intermediate region was detected by the smaller variation of its dispersion. [ABSTRACT FROM AUTHOR]

Purpose: Left ventricular dyssynchrony may predict response to cardiac resynchronization therapy and may well predict adverse cardiac events. Recently, a geometrical approach for dyssynchrony analysis of myocardial perfusion scintigraphy (MPS) was introduced. In this study the feasibility of this geometrical method to detect dyssynchrony was assessed in a population with a normal MPS and in patients with documented ventricular dyssynchrony. Methods: For the normal population 80 patients (40 men and 40 women) with normal perfusion (summed stress score ≤2 and summed rest score ≤2) and function (left ventricular ejection fraction 55-80%) on MPS were selected; 24 heart failure patients with proven dyssynchrony on MRI were selected for comparison. All patients underwent a 2-day stress/rest MPS protocol. Perfusion, function and dyssynchrony parameters were obtained by the Corridor4DM software package (Version 6.1). Results: For the normal population time to peak motion was 42.8 ± 5.1% RR cycle, SD of time to peak motion was 3.5 ± 1.4% RR cycle and bandwidth was 18.2 ± 6.0% RR cycle. No significant gender-related differences or differences between rest and post-stress acquisition were found for the dyssynchrony parameters. Discrepancies between the normal and abnormal populations were most profound for the mean wall motion ( p value <0.001), SD of time to peak motion ( p value <0.001) and bandwidth ( p value <0.001). Conclusion: It is feasible to quantify ventricular dyssynchrony in MPS using the geometrical approach as implemented by Corridor4DM. [ABSTRACT FROM AUTHOR]

Introduction: Coronary artery disease (CAD) is associated with increased dispersion of repolarization and sudden cardiac death. We sought to investigate whether ventricular dyssynchrony is associated with proarrhythmic repolarization dispersion as measured by T-wave alternans (TWA) in patients with CAD. Methods and Results: We evaluated 154 patients (67 ± 9 years, 123 men) with documented CAD, who underwent exercise treadmill testing and echocardiographic examination. TWA was analyzed continuously during treadmill testing in all standard precordial leads by time-domain method. Tissue Doppler imaging was performed to measure inter- and intraventricular dyssynchrony. Increased TWA ≥ 60μV was observed in 42 (27%) patients. There was higher prevalence of females (31 vs 16%, P = 0.04) and greater body mass index (25.7 ± 2.6 vs 24.6 ± 3.0 kg/m2, P = 0.04) in the TWA ≥ 60μV group of patients than the TWA < 60μV group. The index of interventricular dyssynchrony, Ts-RL, was significantly increased (75.6 ± 37.8 vs 59.9 ± 35.9 ms, P = 0.03) but not intraventricular dyssynchrony (all P > 0.05) in patients with TWA ≥ 60 μV compared with those with TWA < 60 μV. In addition, a weak but significant positive correlation was observed between TWA and Ts-RL (r = 0.25, P = 0.003). Multivariate analysis revealed that only Ts-RL (odds ratio 1.02, 95% confidence interval 1.00-1.03, P = 0.013) was independent predictor for increased TWA. Conclusions: Our results demonstrated that interventricular dyssynchrony in patients with CAD is associated with increased TWA. This suggests that interventricular dyssynchrony may contribute to proarrhythmic repolarization dispersion. (PACE 2011; 34:1503-1510) [ABSTRACT FROM AUTHOR]

Electrocardiographic VV Optimization. Introduction: Echocardiographic optimization of the VV interval may improve CRT response, but it is time-consuming and not routinely performed. The aim of this study was to compare the response to cardiac resynchronization therapy (CRT) when the interventricular pacing (VV) interval was optimized by Tissue Doppler Imaging (TDI) to CRT response when it was optimized following QRS width criteria. Methods and Results: The study included 156 consecutive CRT patients with severe heart failure and left bundle-branch block configuration. Atrioventricular interval was selected according to a pulsed Doppler assessment, and VV optimization was randomly assigned to echocardiography (ECHO group, n = 78) or electrocardiography (ECG group, n = 78). Optimal VV was defined for the ECHO group as producing the best LV intraventricular synchrony according to TDI displacement curves and for the ECG group as resulting in the narrowest QRS measured from the earliest deflection. At 6-month follow-up, percentage of echocardiographic responders (defined as neither death nor heart transplantation and a LV end-systolic volume reduction >10%) was higher in the ECG optimized group (50.0% vs 67.9%; P = 0.023), whereas clinical response (defined as neither death nor heart transplantation and >10% improvement in the 6-minute walking test) was similar in both groups (71.8% vs 73.1%; P = 0.858). Conclusions: VV optimization based on QRS width obtained a higher percentage of responders in terms of LV reverse remodeling compared to the TDI method. (J Cardiovasc Electrophysiol, Vol. 22, pp. 1129-1134, October 2011) [ABSTRACT FROM AUTHOR]

Pacemaker implantation remains the only therapeutic option that improves morbidity and mortality for patients with symptomatic bradycardia. However, pacing from the right ventricular apex can induce dyssynchronous activation of the ventricles, increase sympathetic activation, cause abnormalities in myocardial perfusion, worsen cardiac output and endothelial function and may be associated with adverse cardiovascular outcomes. This article reviews the current knowledge on the pathophysiology of pacing-induced cardiovascular disease and current strategies to avoid and mitigate the adverse effects of right ventricular pacing. [ABSTRACT FROM AUTHOR]

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Aims Clinical trial data show that right ventricular pacing worsens cardiovascular outcomes. The underlying pathophysiology of this is undetermined. We studied the effects of right ventricular pacing on cardiac measures of vascular health (endothelial function), ventricular wall stress (B-type natriuretic peptide), and cardiac reserve (cardiac output response to exercise) in subjects with pacemakers. Methods and results Twenty-two subjects [mean age 68.4 ± 8.8 (SD) years] with dual-chamber pacemakers implanted for sino-atrial disease were studied in a randomized crossover study comparing minimal right ventricular pacing [RVP-min; pacing with long atrioventricular delay (AVD)] to maximal right ventricular pacing (RVP-max; pacing with short AVD). Endothelial function was measured with reactive hyperaemia peripheral arterial tonometry. Cardiac output at rest and during exercise was determined using an inert gas rebreathing method. Right ventricular pacing was significantly higher in RVP-max when compared with RVP-min (90 ± 16 vs. 15 ± 20%, P < 0.001). Reactive hyperaemia peripheral arterial tonometry index was significantly lower after RVP-max vs. RVP-min (1.73 ± 0.33 vs. 1.96 ± 0.37, P < 0.05). B-type natriuretic peptide was not significantly different between pacing modes (113 ± 80 vs. 104 ± 108 pg/mL, P = NS). Cardiac output at peak exercise was significantly lower during RVP-max (7.65 ± 3.15 vs. 7.05 ± 2.61 L/min, P < 0.05). Conclusion Right ventricular pacing is associated with worsened endothelial function and cardiac reserve. [ABSTRACT FROM PUBLISHER]

Cardiac resynchronization therapy is a key non-pharmacological treatment strategy for drug-refractory moderate-to-severe symptomatic heart failure in the presence of compromised left ventricular function and ventricular conduction delay. Because not all patients with conventional criteria benefit from CRT, continuous efforts have been directed toward improving patient selection; in particular, emerging echocardiographic criteria such as regional and global myocardial strains are being investigated to better predict CRT response. In the meantime, growing evidence from large randomized controlled trials (RCTs, REVERSE, and MADIT-CRT) has demonstrated that even mildly symptomatic patients may benefit from CRT. The role of CRT in heart failure patients with narrow QRS, however, remains to be defined in the scheme of larger RCTs (such as EchoCRT) as the ones carried out thus far (RethinQ and ESTEEM-CRT). Important experimental data derived from animal heart failure models are gradually elucidating the complex pathophysiological basis of cardiac dyssynchrony, which involves diffuse alterations from genome to structure. At the same time, technological breakthroughs, such as wireless endocardial cardiac pacing, will render the prospect of delivering CRT more precisely and more effectively, a reality in the near future. [ABSTRACT FROM AUTHOR]

Aims Cardiac resynchronization therapy (CRT) diminishes cardiac apoptosis and improves systolic function in heart failure (HF) patients with ventricular dyssynchrony. Plasma annexin A5 (AnxA5), a protein related to cellular damage, is associated with systolic dysfunction. We investigated whether the response to CRT is associated with plasma AnxA5. We also studied AnxA5 overexpression effects in HL-1 cardiomyocytes. Methods and results AnxA5 ELISA was performed in plasma from 57 patients with HF and ventricular dyssynchrony at baseline and after 1 year of CRT. Patients were categorized as responders if they presented both a reduction in left ventricular (LV) end-systolic volume index (LVESVi) >10% and an increase in LV ejection fraction (LVEF) >10%. HL-1 cells were transfected with human AnxA5 cDNA, and AnxA5, PKC, Akt, p38MAPK, Bcl-2, mitochondrial integrity, caspase-3, and ATP were assessed. At baseline, an increased plasma AnxA5 level was associated with decreased LVEF and increased LVEDVi values (P < 0.05). No differences in baseline AnxA5 were observed between responders and non-responders. After CRT, AnxA5 decreased (P = 0.001) in responders but remained unchanged in non-responders. Final values of AnxA5 were independently associated with LVEF (r = −0.387, P = 0.003) and LVESVi (r = 0.403, P = 0.004) in all patients. Compared with control cells, AnxA5-transfected cells exhibited AnxA5 overexpression, decreased PKC and Akt and increased p38MAPK and Bcl-2 phosphorylation, loss of mitochondrial integrity, caspase-3 activation, and decreased ATP. Conclusion CRT-induced LV reverse remodelling is associated with reduction in plasma AnxA5. The excess of AnxA5 is detrimental for HL-1 cardiomyocytes. Collectively, these data suggest that the beneficial effects of CRT might be related to an AnxA5 decrease. [ABSTRACT FROM PUBLISHER]

Aims We sought to determine whether inter- or intra-ventricular systolic dyssynchrony contributes to the occurrence of elevated pulmonary artery systolic pressure (PASP) in patients with coronary artery disease (CAD). Methods and results One hundred and fifty-three consecutive CAD patients with preserved left ventricular ejection fraction (LVEF >40%) were enrolled. Detailed echocardiography was performed to measure PASP, inter-ventricular dyssynchrony (Ts-RL: time difference between lateral and right free wall), and intra-ventricular dyssynchrony (Ts-SD, standard deviation of time to peak systolic velocity of 12 LV segments; Ts-12, maximal difference in Ts between any 2 of 12 LV segments; Ts-6-basal, maximal difference in Ts between any 2 of 6 basal LV segments). Elevated PASP (>35 mmHg) was confirmed in 46 patients who had significantly prolonged intra-ventricular dyssynchrony (Ts-SD: 49.9 ± 19.6 vs.37.9 ± 19.8 ms; Ts-12: 147.9 ± 56.4 vs.110.9 ± 53.9 ms; Ts-6-basal: 114.2 ± 51.9 vs. 85.7 ± 48.5 ms, all P < 0.01) and inter-ventricular dyssynchrony (Ts-RL: 78.7 ± 46.4 vs. 62.7 ± 34.3 ms, P = 0.019) compared with those without elevated PASP. Indexes of intra- and inter-ventricular dyssynchrony and LV filling pressure (E/e′) were significantly correlated with PASP. Multivariate analysis showed that left atrial dimension [odds ratio (OR) 4.23, 95% confidence interval (CI) 1.64–10.90], E/e′ septal (OR 1.15, 95% CI 1.04–1.27), pulmonary vascular resistance (OR 5.38, 95% CI 1.55–18.74), and Ts-RL (OR 1.02, 95% CI 1.01–1.03) were independent predictors for the occurrence of elevated PASP (all P < 0.05). Conclusion Elevated PASP is common in CAD patients with preserved LVEF and is associated with LV diastolic dysfunction and LV mechanical dyssynchrony. [ABSTRACT FROM AUTHOR]

Background: Few studies have assessed the long-term effects of cardiac resynchronization therapy (CRT) in patients with advanced heart failure (HF) and previously right ventricular apical pacing (RVAP). Aims: To assess the clinical and hemodynamic impact of upgrading to biventricular pacing in patients with severe HF and permanent RVAP in comparison with patients who had CRT implantation as initial therapy. Methods and Results: Thirty-nine patients with RVAP, advanced HF (New York Heart Association [NYHA] III–IV), and severe depression of left ventricular ejection fraction (LVEF) were upgraded to biventricular pacing (group A). Mean duration of RVAP before upgrading was 41.8 ± 13.3 months. Clinical and echocardiographic results were compared to those obtained in a group of 43 patients with left bundle branch block and similar clinical characteristics undergoing “primary” CRT (group B). Mean follow-up was 35 ± 10 months in patients of group A and 38 ± 12 months in group B. NYHA class significantly improved in groups A and B. LVEF increased from 0.23 ± 0.07 to 0.36 ± 0.09 (P < 0.001) and from 0.26 ± 0.02 to 0.34 ± 0.10 (P < 0.001), respectively. Hospitalizations were reduced by 81% and 77% (P < 0.001). Similar improvements in echocardiographic signs of ventricular desynchronization were also observed. Conclusion: Patients upgraded to CRT exhibit long-term clinical and hemodynamic benefits that are similar to those observed in patients treated with CRT as initial strategy. (PACE 2010; 841–849) [ABSTRACT FROM AUTHOR]

Background: Optimal treatment of right ventricular (RV) dysfunction observed in patients after tetralogy of Fallot (TOF) repair is unclear. Studies of biventricular (BiV) stimulation in patients with congenital heart disease have been retrospective or have included patients with heterogeneous disorders. Objective: The purpose of this study was to determine the effects on cardiac function of stimulating at various cardiac sites in an animal model of RV dysfunction and dyssynchrony and in eight symptomatic adults with repaired TOF. Methods: Pulmonary stenosis and regurgitation as well as RV scars were induced in 15 piglets to mimic repaired TOF. The hemodynamic effects of various configurations of RV and BiV stimulation were compared with sinus rhythm (SR) 4 months after surgery. In eight adults with repaired TOF, RV and left ventricular (LV) dP/dtmax were measured invasively during SR, apical RV stimulation, and BiV stimulation. Results: At 4 months, RV dilation, dysfunction, and dyssynchrony were present in all piglets. RV stimulation caused a decrease in LV function but no change in RV function. In contrast, BiV stimulation significantly improved LV and RV function (P < .05). Echocardiography and epicardial electrical mapping showed activation consistent with right bundle branch block during SR and marked resynchronization during BiV stimulation. In patients with repaired TOF, BiV stimulation increased significantly RV and LV dP/dtmax (P < .05). Conclusion: In this swine model of RV dysfunction and in adults with repaired TOF, BiV stimulation significantly improved RV and LV function by alleviating electromechanical dyssynchrony. [Copyright &y& Elsevier]

Background: It has been hypothesized that a long-term response to cardiac resynchronization therapy (CRT) could correlate with myocardial viability in patients with left ventricular (LV) dysfunction. Contractile reserve and viability in the region of the pacing lead have not been investigated in regard to acute response after CRT. Methods: Fifty-one consecutive patients with advanced heart failure, LV ejection fraction ≤ 35%, QRS duration > 120 ms, and intraventricular asynchronism ≥ 50 ms were prospectively included. The week before CRT implantation, the presence of viability was evaluated using dobutamine stress echocardiography. Acute responders were defined as a ≥15% increase in LV stroke volume. Results: The average of viable segments was 5.8 ± 1.9 in responders and 3.9 ± 3 in nonresponders (P = 0.03). Viability in the region of the pacing lead had an excellent sensitivity (96%), but a low specificity (56%) to predict acute response to CRT. Mitral regurgitation (MR) was reduced in 21 patients (84%) with acute response. The presence of MR was a poor predictor of response (sensibility 93% and specificity 17%). However, combining the presence of MR and viability in the region of the pacing lead yields a sensibility (89%) and a specificity (70%) to predict acute response to CRT. Conclusion: Myocardial viability is an important factor influencing acute hemodynamic response to CRT. In acute responders, significant MR reduction is frequent. The combined presence of MR and viability in the region of the pacing lead predicts acute response to CRT with the best accuracy. (Echocardiography 2010;27:50-57) [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The relationships between filtered QRS duration and ventricular dyssynchrony were studied. Methods: We measured filtered QRS duration on signal-averaged electrocardiography and analyzed tissue Doppler imaging in chronic heart failure patients with ejection fraction less than 50%. Results: In 64 patients, interventricular and intraventricular dyssynchronies were observed in 25 and 38 patients, respectively. All patients with interventricular dyssynchrony were associated with intraventricular dyssynchrony. Filtered QRS showed 0.82 and 0.78 of the area under the curve (AUC) in the receiver operating characteristic curve (ROC) for the detection of interventricular and intraventricular dyssynchrony, respectively, with 89.7% and 96.2% specificity and 52.0% and 52.6% sensitivity, with cutoff values of 174 and 153 milliseconds. Specificity and sensitivity as well as AUC were lower in the ROC of QRS duration than filtered QRS duration. Conclusion: Filtered QRS duration provided more reliable information to estimate ventricular dyssynchrony in patients with reduced ventricular ejection fraction than QRS duration did. [Copyright &y& Elsevier]

Abstract: The electrocardiographic diagnosis of left ventricular hypertrophy (LVH) has been centered on improving the diagnostic sensitivity and specificity of the method, using criteria whose precise relationship to increased left ventricular mass are not established. Although the electrocardiogram (ECG) has been displaced to a secondary role in the prediction of left ventricular mass, ECG/LVH has been shown to be a strong predictor of morbidity and early mortality. There are strong clues that each of the parameters in ECG/LVH is related to cardiac contractility and ejection. It is suggested that research be redirected to an exploration of these relationships and predicted that this will lead to both a better understanding of this venerable tool and an improvement in its usefulness to the clinician and patient. [Copyright &y& Elsevier]

Cardiac pacing is the only effective treatment for patients with sick sinus syndrome and atrioventricular conduction disorders. In cardiac pacing, the endocardial pacing lead is typically positioned at the right ventricular (RV) apex. At the same time, there is increasing indirect evidence, derived from large pacing mode selection trials and observational studies, that conventional RV apical pacing may have detrimental effects on cardiac structure and left ventricular function, which are associated with the development of heart failure. These detrimental effects may be related to the abnormal electrical and mechanical activation pattern of the ventricles (or ventricular dyssynchrony) caused by RV apical pacing. Still, it remains uncertain if the deterioration of left ventricular function as noted in a proportion of patients receiving RV apical pacing is directly related to acutely induced left ventricular dyssynchrony. The upgrade from RV pacing to cardiac resynchronization therapy may partially reverse the deleterious effects of RV pacing. It has even been suggested that selected patients with a conventional pacemaker indication should receive cardiac resynchronization therapy to avoid the deleterious effects. This review will provide a contemporary overview of the available evidence on the detrimental effects of RV apical pacing. Furthermore, the available alternatives for patients with a standard pacemaker indication will be discussed. In particular, the role of cardiac resynchronization therapy and alternative RV pacing sites in these patients will be reviewed. [Copyright &y& Elsevier]

Objectives: This study sought to investigate the prevalence and mechanisms underlying right ventricular (RV) dyssynchrony in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) using tissue Doppler echocardiography (TDE). Background: An ARVD/C is characterized by fibrofatty replacement of RV myocardium and RV dilation. These pathologic changes may result in electromechanical dyssynchrony. Methods: Echocardiography, both conventional and TDE, was performed in 52 ARVD/C patients fulfilling Task Force criteria and 25 control subjects. The RV end-diastolic and -systolic areas, right ventricular fractional area change (RVFAC), and left ventricular (LV) volumes and function were assessed. Mechanical synchrony was assessed by measuring differences in time-to-peak systolic velocity (TSV) between the RV free wall, ventricular septum, and LV lateral wall. An RV dyssynchrony was defined as the difference in TSV between the RV free wall and the ventricular septum, >2 SD above the mean value for control subjects. Results: The mean difference in RV TSV was higher in ARVD/C compared with control subjects (55 ± 34 ms vs. 26 ± 15 ms, p < 0.001). Significant RV dyssynchrony was not noted in any of the control subjects. Based on a cutoff value of 56 ms, significant RV dyssynchrony was present in 26 ARVD/C patients (50%). Patients with RV dyssynchrony had a larger RV end-diastolic area (22 ± 5 cm2 vs. 19 ± 4 cm2, p = 0.02), and lower RVFAC (29 ± 8% vs. 34 ± 8%, p = 0.03) compared with ARVD/C patients without RV dyssynchrony. No differences in QRS duration, LV volumes, or function were present between the 2 groups. Conclusions: An RV dyssynchrony may occur in up to 50% of ARVD/C patients, and is associated with RV remodeling. This finding may have therapeutic and prognostic implications in ARVD/C. [Copyright &y& Elsevier]

The article presents a study on the changes in ion channel subunit expression of cardiac Purkinje fibers (PFs) in dogs with ventricular tachypacing-induced congestive heart failure (CHF). In this study, action potential properties and conduction velocity measurements of protein-enriched samples from dogs were determined and immunohistochemistry was also employed. Results show a decrease in the expression of subunits which indicates the significance of CHF on PF ion channel subunit expression.

Abstract: Objective: The purpose of this study is to investigate the potential to induce electrical remodeling by chronic right ventricular apical (RVA) in patients with sinus node dysfunction. Methods: Ninety-two patients with sinus node dysfunction who underwent initial pacemaker implantation were included in the study. During routine clinic visits, electrocardiograms and echocardiograms were recorded. Forty-five patients were also studied as controls. Results: During a mean follow-up time of 3.3 ± 0.5 years, the intrinsic QRS duration increased from 87 ± 9 milliseconds before device implantation to 94 ± 10 milliseconds (P < .001). The left ventricular end-diastolic diameter increased from 46 ± 3 to 50 ± 4 mm (P < .001), and the left ventricular ejection fraction decreased from 63% ± 4% to 57% ± 5% (P < .001). Logistic regression analysis revealed that elderly age at the time of pacemaker implantation (odds ratio [OR], 3.41; 95% confidence interval [CI], 1.07-10.90; P = .04), RVA pacing (OR, 3.91; 95% CI, 1.10-13.89; P = .03), and coronary artery disease (OR, 7.33; 95% CI, 1.09-50.29; P = .04) were independent predictors of the prolongation of intrinsic QRS duration. Conclusions: The present study indicated that chronic RVA pacing may lead to a prolongation of intrinsic QRS duration, which could be independently predicted by elderly age, chronic RVA pacing, and the presence of coronary artery disease. [Copyright &y& Elsevier]

Abstract: Factorial phase analysis (FaPI) represents an alternative method to Fourier phase analysis (FoPI) in the evaluation and detection of abnormalities on cardiac contraction patterns, but it has limitations in representing the sequence in abnormal contraction patterns. In this work we propose a modified factorial phase image (FaPIm) that incorporates more complete information regarding the ventricular contraction sequence. In particular, we analyze and evaluate the contribution of the third eigenimage, in the presence of ventricular dyssynchrony, which has not been sufficiently explored in the literature. We have validated the proposed FaPIm using two Equilibrium Radionuclide Angiography (ERNA) sets of images obtained with a dynamic cardiac phantom and with a numerically simulated phantom. Also, we have tested the proposed representation for a control group of 23 normal subjects and for a sample of 15 patients with Complete Left Bundle Branch Block (LBBB). Whereas FoPI allows us to obtain an image that synthesizes ventricular contraction with the smallest dispersion around the mean values, FaPI and FaPIm show that external areas surrounding ventricular cavities present more dephasing than the rest of the ventricular region and contain more detailed information about the progression of contraction. Also, in the presence of an abnormal contraction pattern, the magnitude of the third eigenvalue was greater than the corresponding eigenvalue obtained for normal simulations. The dispersion plots obtained for a normal contraction pattern show that left ventricle (LV) and right ventricle (RV) information overlap. Therefore, when there is a dyssynchrony between LV and RV contraction it becomes necessary to incorporate the information corresponding to the third factor to achieve a clear separation between regions. In the comparison of the indices of control and LBBB populations, FaPIm shows significant differences in five out of six contraction indices, showing its promising value as a clinical tool. [Copyright &y& Elsevier]

In recent years, concerns have been raised about possible harmful effects of long-term right ventricular (RV) apical pacing. These detrimental effects may be related to changes in left ventricular (LV) mechanics during RV apical pacing. As a consequence, alternative RV pacing sites have been proposed, and in selected patients an upgrade from RV to biventricular pacing may be considered. Novel two-dimensional (2D) speckle tracking strain imaging allows detailed evaluation of LV mechanics, including LV mechanical dyssynchrony, LV strain and LV torsion. In this review, the role of speckle tracking strain imaging in the evaluation of LV function in patients with RV apical pacing will be reviewed. The effects of RV apical pacing on LV mechanical dyssynchrony, LV strain and LV torsion will be discussed. In addition, the role of speckle tracking strain imaging in the selection of the optimal (alternative) RV pacing site and in the selection of patients who may benefit from an upgrade from RV apical pacing to biventricular pacing will be reviewed. [ABSTRACT FROM AUTHOR]

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Echocardiography is important in the follow-up of children with permanent pacemakers due to the risk for cardiomyopathy. However, the value of standard measurements is unclear in the setting of expected dyssynchrony caused by ventricular pacing. The study sought to assess and compare echocardiographic parameters of ventricular function in children with chronic ventricular pacing. Echocardiographic studies of patients with normal cardiac anatomy and ventricular pacing for heart block were retrospectively evaluated for routine measurements of systolic and diastolic ventricular function. In 60 echocardiograms that were analyzed, fractional shortening (FS) had moderate correlation with ejection fraction (EF; R = 0.64, p < 0.001) while tissue Doppler (TDI) s waves had poor correlation to EF in the assessment of systolic function. When excluding the two patients with clinical cardiomyopathy, EF and FS had near normal mean z-scores (−0.26 ± 1.68 and 0.07 ± 1.65, respectively). For diastolic function, mean left atrial (LA) area measurements were also normal (mean z-score −0.01 ± 0.9). However, TDI measures and E/A wave ratio had poor correlation and appeared to underestimate diastolic function. FS and EF are moderately correlated to each other and may both be appropriate in the evaluation of systolic function in chronically paced children. TDI values may be misleading, measuring low diastolic function despite normal LA area. • Echocardiographic assessment can be challenging in ventricularly-paced children • Fractional shortening appears to moderately correlate to ejection fraction • Despite pacing, fractional shortening may be a valid measure of systolic function • Diastolic measures such as tissue Doppler likely underestimate diastolic function [ABSTRACT FROM AUTHOR]

The purpose of the study is to examine prognostic values of cardiac I-123 metaiodobenzylguanidine (MIBG) uptake and cardiac dyssynchrony in patients with dilated cardiomyopathy (DCM). Ninety-four patients with non-ischemic DCM underwent I-123 MIBG imaging for assessing cardiac sympathetic innervation and equilibrium radionuclide angiography. Mean phase angles and SD of the phase histogram were computed for both right ventricular (RV) and left ventricular (LV). Phase measures of interventricular (RV–LV) and intraventricular (SD–RV and SD–LV) asynchrony were computed. Most patients were receiving beta-blockers (89%) and angiotensin-converting enzyme inhibitors (88%). One patient (1%) was lost to follow-up, six had cardiac death (6.4%), eight had heart transplantation (8.6%), and seven had unplanned hospitalization for heart failure (7.5%; mean follow-up: 37 ± 16 months). Patients with poor clinical outcome were older, had higher The New York Heart Association functional class, impaired right ventricular ejection fraction and left ventricular ejection fraction, and impaired cardiac I-123 MIBG uptake. On multivariate analysis, I-123 MIBG heart-to-mediastinum (H/M) uptake ratio <1.6 was the only predictor of both primary (cardiac death or heart transplantation, RR = 7.02, p < 0.01) and secondary (cardiac death, heart transplantation, or recurrent heart failure, RR = 8.10, p = 0.0008) end points. In patients receiving modern medical therapy involving beta-blockers, I-123 MIBG uptake, but not intra-LV asynchrony, was predictive of clinical outcome. The impact of beta-blockers on the prognostic value of ventricular asynchrony remains to be clarified. [ABSTRACT FROM AUTHOR]

Objective: To determine the effect of cardiac resynchronization therapy (CRT) on sympathetic nervous function in heart failure (HF). Background: Neurohormonal dysregulation and cardiac autonomic dysfunction are associated with HF and contribute to HF progression and its poor prognosis. We hypothesized that mechanical resynchronization improves cardiac sympathetic function in HF. Methods: Sixteen consecutive patients receiving CRT for advanced cardiomyopathy and 10 controls were included in this prospective study. NYHA class, 6-minute walk distance, echocardiographic parameters, plasma norepinephrine (NE) were assessed at baseline, 3-month and 6-month follow-up. Cardiac sympathetic function was determined by 123iodine metaiodobenzylguanidine (123I-MIBG) scintigraphy and 24-hour ambulatory electrocardiography. Results: Along with improvement in NYHA class (3.1 ± 0.3 to 2.1 ± 0.4, P < 0.001) and LVEF (23 ± 6% to 33 ± 12%, P < 0.001), delayed heart/mediastinum (H/M) 123I-MIBG ratio increased significantly (1.8 ± 0.7 to 2.1 ± 0.6, P = 0.04) while the H/M 123I-MIBG washout rate decreased significantly (54 ± 25% to 34 ± 24%, P = 0.01) from baseline to 6-month follow-up. The heart rate variability (HRV) measured in SD of normal-to-normal intervals also increased significantly from baseline (82 ± 30 ms) to follow-up (111 ± 32 ms, P = 0.04). The improvement in NYHA after CRT was significantly associated with baseline 123I-MIBG H/M washout rate (r = 0.65, P = 0.03). The improvement in LVESV index was associated with baseline 123I-MIBG delayed H/M ratio (r =−0.67, P = 0.02) and H/M washout rate (r = 0.65, P = 0.03). Conclusion: After CRT, improvements in cardiac symptoms and LV function were accompanied by rebalanced cardiac autonomic control as measured by 123I-MIBG and HRV. [ABSTRACT FROM AUTHOR]

Introduction: Patients with heart block have conventionally received a pacemaker that stimulates the right ventricular apex (RVA) to restore heart rate control. While RVA pacing has been shown to create systolic dyssynchrony acutely, dyssynchrony can also occur in diastole. The effects of acute RVA pacing on diastolic synchrony have not been investigated. RVA pacing acutely impairs diastolic function by increasing the time constant of relaxation, decreasing the peak lengthening rate and decreasing peak negative dP/dt. We therefore hypothesized that acute RVA pacing would cause diastolic dyssynchrony in addition to creating systolic dyssynchrony. Methods and Results: Fourteen patients (13 ± 4 years old) with non-preexcited supraventricular tachycardia underwent ablation therapy with subsequent testing to confirm elimination of the tachycardia substrate. Normal cardiac structure and function were then documented on two-dimensional echocardiography and 12-lead electrocardiography prior to enrollment. Tissue Doppler images were collected during normal sinus rhythm (NSR), right atrial appendage pacing (AAI), and VVI-RVA pacing during the postablation waiting interval. Systolic and diastolic dyssynchrony were quantified using cross-correlation analysis of tissue Doppler velocity curves. Systolic dyssynchrony increased 81% during RVA pacing relative to AAI and NSR (P < 0.01). Diastolic synchrony was not affected by the different pacing modes (P = 0.375). Conclusion: Acute dyssynchronous activation of the LV created by RVA pacing resulted in systolic dyssynchrony with preserved diastolic synchrony in pediatric patients following catheter ablation for treatment of supraventricular tachycardia. Our results suggest that systolic and diastolic dyssynchrony are not tightly coupled and may develop through separate mechanisms. [ABSTRACT FROM AUTHOR]

Background: There are few studies on cardiac resynchronization therapy (CRT) in heart failure (HF) patients with preexisting right ventricular (RV) pacing. The purpose of this study was to determine the efficacy of CRT upgrading in RV-paced patients and the predictivity of electromechanical dyssynchrony parameters (EDP) evaluated by standard echocardiography (ECHO) and tissue Doppler imaging (TDI). Methods: Thirty-eight consecutive patients with HF [New York Heart Association (NYHA) class III or IV, LVEF < 35%], prior continuous RV pacing, and absence of atrial fibrillation were enrolled in the presence of a paced QRS ≥ 150 ms and evaluated by ECHO and TDI. A responder was defined as a patient with a favorable change in NYHA class and neither HF hospitalization nor death, plus an absolute increase of LVEF ≥ 10 units. Results: At six-months follow-up, the whole study population had significant improvement in symptoms, systolic function, and QRS duration (P < 0.001); 32 (84%) patients had a favorable clinical outcome, 25 (66%) were considered responders according to the previous definition. Postimplant QRS was similarly reduced in both responders and nonresponders, whereas EDP had a significant improvement only in responders (P < 0.05). Using EDP, 23 (79%) patients were responders compared with 2 (22%) patients without mechanical dyssynchrony (P = 0.002). Conclusions: In HF patients with previous RV pacing, CRT is effective to improve clinical, functional outcome, and LV performance and to reduce electromechanical dyssynchrony in a large proportion of patients. Dyssynchrony evaluated by standard and TDI ECHO can be useful for CRT selection of paced patients. [ABSTRACT FROM AUTHOR]

Abstract: Background: Cardiac dyssynchrony due to intraventricular conduction delay produces heterogeneous regional wall stress and worsens arrhythmia susceptibility in failing hearts. We examined whether chronic dyssynchrony per se induces regionally heterogeneous electrophysiological remodeling. Methods and results: Adult dogs (n =9) underwent left bundle branch radiofrequency ablation (QRS duration increased from 50±7 to 104±7 ms); 6 untreated dogs served as controls. A subset of ablated (n =3) and control (n =4) dogs underwent tagged MR imaging to confirm ablation-induced left ventricular (LV) dyssynchrony. Four weeks later, hearts were excised and early (anterior)- and late (lateral)-activated myocardial segments were isolated. Conduction velocity (CV), action potential duration (APD), and refractory period (RP) of paced, arterially perfused myocardial wedges were studied by extracellular and optical mapping, and arrhythmia susceptibility was assessed by programmed stimulation. Regional stress-response kinase, calcium cycling, and gap junction protein expression were assayed by Western blotting, and the subcellular distribution of connexin43 was analyzed by immunofluorescence microscopy. CV, APD, and RP were significantly reduced in the late-activated, lateral wall of dyssynchronous hearts compared to the anterior wall. Normal differences in CV (endocardial>epicardial) were reversed in the dyssynchronous lateral LV. While the total expression of connexin43 was unaltered in dyssynchronous models, its subcellular location was redistributed in late-activated myocardium from intercalated discs to lateral myocyte membranes. Arrhythmias were rare in tissue from normal and dyssynchronous models. Total expression of calcium-cycling proteins (sarcoplasmic reticulum Ca2 +-ATPase and phospholamban) and the stress-response kinase phospho-ERK did not vary regionally in either model. Conclusions: Dyssynchrony even in the absence of LV dysfunction induces regionally specific changes in conduction and repolarization. These changes support a novel mechanism linking mechanical dyssynchrony to persistent electrophysiological remodeling and heterogeneity. [Copyright &y& Elsevier]

Approximately one third of patients with congestive heart failure and systolic dysfunction have an intraventricular conduction delay that is manifested as a QRS duration >120 ms. An intraventricular conduction delay adversely affects ventricular performance by causing dyssynchrony in ventricular activation. When ventricular dyssynchrony is present, simultaneous left and right ventricular pacing or cardiac resynchronization therapy can improve ventricular synchrony. This can lead to an improvement in hemodynamics, ventricular remodeling, mitral regurgitation, exercise capacity and quality of life. Candidates for cardiac resynchronization therapy include patients with advanced congestive heart failure that is refractory to medical therapy, a QRS duration >130 ms, left ventricular ejection fraction <0.35 and sinus rhythm. Because patients who are candidates for biventricular pacing are at high risk of sudden death, they should be considered for implantation of a biventricular pacing device that also provides defibrillation therapy. This paper reviews biventricular pacing for congestive heart failure, including results of acute hemodynamic studies and randomized clinical trials, patient and device selection, and procedural issues. Copyright © 2004 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]