Long-term left ventricular pacing: assessment and comparison with biventricular pacing in patients with severe congestive heart failure

Biventricular versus left ventricular only stimulation: an echocardiographic substudy of the B-LEFT HF trial

BACKGROUND

The noninferiority of left ventricular pacing alone (LVp) compared with biventricular pacing (BIV) has not been yet definitely documented. In this study, we reviewed all the original echocardiographic measures of the Biventricular versus Left Univentricular Pacing with ICD Back-up in Heart Failure Patients (B-LEFT HF) trial in order to investigate mechanisms underlying LV remodelling with both pacing modalities.

METHODS

Patients with New York Heart Association functional class (NYHA) III or IV despite optimal medical therapy, LVEF 35% or less, left ventricular end-diastolic diameter (LVEDD) more than 55 mm, QRS duration at least 130 ms were randomized to BIV or LVp for 6 months. The primary end point was a composite of at least 1 point decrease in NYHA class and at least 5 mm decrease in left ventricular end-systolic diameter (LVESD). An additional end point was a LVp reverse remodelling defined as at least 10% decrease in LVESD. Mitral regurgitation and all echocardiographic measures were reassessed after 6-month follow-up.

RESULTS

One hundred and forty-three patients were enrolled. Seventy-six patients were in the BIV and 67 were in the LVp group. Left ventricular volumes decreased significantly without difference between groups (P = 0.8447). Similarly, left ventricular diameters decreased significantly in both groups with a significant decrease in LVESD with BIV (P < 0.0001), but not with LVp (P = 0.1383). LVEF improved in both groups without difference (P = 0.8072). Mitral regurgitation did not improve either with BIV, or with LVp.

CONCLUSION

The echocardiographic sub-analysis of B-LEFT study showed the substantial equivalence of LVp in favouring left ventricular reverse remodelling as compared with BIV.

Comparison of novel ventricular pacing strategies using an electro-mechanical simulation platform

AIMS

Focus of pacemaker therapy is shifting from right ventricular (RV) apex pacing (RVAP) and biventricular pacing (BiVP) to conduction system pacing. Direct comparison between the different pacing modalities and their consequences to cardiac pump function is difficult, due to the practical implications and confounding variables. Computational modelling and simulation provide the opportunity to compare electrical, mechanical, and haemodynamic consequences in the same virtual heart.

METHODS AND RESULTS

Using the same single cardiac geometry, electrical activation maps following the different pacing strategies were calculated using an Eikonal model on a three-dimensional geometry, which were then used as input for a lumped mechanical and haemodynamic model (CircAdapt). We then compared simulated strain, regional myocardial work, and haemodynamic function for each pacing strategy. Selective His-bundle pacing (HBP) best replicated physiological electrical activation and led to the most homogeneous mechanical behaviour. Selective left bundle branch (LBB) pacing led to good left ventricular (LV) function but significantly increased RV load. RV activation times were reduced in non-selective LBB pacing (nsLBBP), reducing RV load but increasing heterogeneity in LV contraction. LV septal pacing led to a slower LV and more heterogeneous LV activation than nsLBBP, while RV activation was similar. BiVP led to a synchronous LV-RV, but resulted in a heterogeneous contraction. RVAP led to the slowest and most heterogeneous contraction. Haemodynamic differences were small compared to differences in local wall behaviour.

CONCLUSION

Using a computational modelling framework, we investigated the mechanical and haemodynamic outcome of the prevailing pacing strategies in hearts with normal electrical and mechanical function. For this class of patients, nsLBBP was the best compromise between LV and RV function if HBP is not possible.

Determinants of LV dP/dtmax and QRS duration with different fusion strategies in cardiac resynchronisation therapy

BACKGROUND

We designed this study to assess the acute effects of different fusion strategies and left ventricular (LV) pre-excitation/post-excitation on LV dP/dtmax and QRS duration (QRSd).

METHODS

We measured LV dP/dtmax and QRSd in 19 patients having cardiac resynchronisation therapy (CRT). Two groups of biventricular pacing were compared: pacing the left ventricle (LV) with FUSION with intrinsic right ventricle (RV) activation (FUSION), and pacing the LV and RV with NO FUSION with intrinsic RV activation. In the NO FUSION group, the RV was paced before the expected QRS onset. A quadripolar LV lead enabled distal, proximal and multipoint pacing (MPP). The LV was stimulated relative in time to either RV pace or QRS-onset in four pre-excitation/post-excitation classes (PCs). We analysed the interactions of two groups (FUSION/NO FUSION) with three different electrode configurations, each paced with four different degrees of LV pre-excitation (PC1-4) in a statistical model.

RESULTS

LV dP/dtmax was higher with NO FUSION than with FUSION (769±46 mm Hg/s vs 746±46 mm Hg/s, p<0.01), while there was no difference in QRSd (NO FUSION 156±2 ms and FUSION 155±2 ms). LV dP/dtmax and QRSd increased with LV pre-excitation compared with pacing timed to QRS/RV pace-onset regardless of electrode configuration. Overall, pacing LV close to QRS-onset (FUSION) with MPP shortened QRSd the most, while LV dP/dtmax increased the most with LV pre-excitation.

CONCLUSION

We show how a beneficial change in QRSd dissociates from the haemodynamic change in LV dP/dtmax with different biventricular pacing strategies. In this study, LV pre-excitation was the main determinant of LV dP/dtmax, while QRSd shortens with optimal resynchronisation.

Comparison of left ventricular and biventricular pacing: Rationale and clinical implications

Cardiac resynchronization therapy constitutes a cornerstone in advanced heart failure treatment, when there is evidence of dyssynchrony, especially by electrocardiography. However, it is plagued both by persistently high (~30%) rates of nonresponse and by deterioration of right ventricular function, owing to iatrogenic dyssynchrony in the context of persistent apical pacing to ensure delivery of biventricular pacing. Left ventricular pacing has long been considered an alternative to standard biventricular pacing and can be achieved as easily as inserting a single pacing electrode in the coronary sinus. Although monoventricular left ventricular pacing has been proven to yield comparable results with the standard biventricular modality, it is the advent of preferential left ventricular pacing, combining both the powerful resynchronization potential of multipolar coronary sinus and right-sided electrodes acting in concert and the ability to preserve intrinsic, physiological right ventricular activation. In this review, we aim to present the underlying principles and modes for delivering left ventricular pacing, as well as to highlight advantages of preferential over monoventricular configuration. Finally, current clinical evidence, following implementation of automated algorithms, regarding performance of left ventricular as compared with biventricular pacing will be discussed. It is expected that the field of preferential left ventricular pacing will grow significantly over the following years, and its combination with other advanced pacing modalities may promote clinical status and prognosis of patients with advanced dyssynchronous heart failure.

'Optimized' LV only pacing using a dual chamber pacemaker as a cost effective alternative to CRT

Background

Cardiac Resynchronization therapy (CRT) remains largely under-used in developing countries owing to the high cost of therapy. In this pilot study, we explore ‘optimized’ Left Ventricle Only Pacing (LVOP) as a cost effective alternative to cardiac resynchronization therapy in selected patients with heart failure.

Hypothesis

In economically poorer patients with heart failure, left bundle branch block (LBBB) and intact AV node conduction, synchronization can be obtained using a dual chamber pacemaker (leads in right atrium and Left ventricle) with the help of 2D strain imaging.

Methods and results

4 patients underwent LVOP for symptomatic heart failure. Post procedure ‘optimization’ was done using 12 lead electrocardiography and 2D- Strain imaging. Difference between Time to Peak longitudinal strain and Aortic valve Closure (Diff T_PL-AC) was calculated for each segment at different AV delays and the AV delay with the smallest Diff T_PL-AC was programmed. The mean AV delay that resulted in electrical and mechanical synchrony was 150 ms. After a mean follow up of 6 months, all patients had improved by at least 1 NYHA class. The mean reduction in QRS duration post procedure was −54.5 ± 22.82 ms and the mean improvement in EF was 7 ± 2.75%.

Conclusion

Optimized LVOP using 2D strain and ECG can be a cost-effective alternative to CRT in patients with LBBB, heart failure and normal AV node conduction.

Role of abnormal repolarization in the mechanism of cardiac arrhythmia

In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K⁺ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca²⁺ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na⁺ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K⁺ channel (dofetilide).

The influence of right ventricular stimulation on acute response to cardiac resynchronisation therapy

Background

The contribution of right ventricular (RV) stimulation to cardiac resynchronisation therapy (CRT) remains controversial. RV stimulation might be associated with adverse haemodynamic effects, dependent on intrinsic right bundle branch conduction, presence of scar, RV function and other factors which may partly explain non-response to CRT. This study investigates to what degree RV stimulation modulates response to biventricular (BiV) stimulation in CRT candidates and which baseline factors, assessed by cardiac magnetic resonance imaging, determine this modulation.

Methods and results

Forty-one patients (24 (59 %) males, 67 ± 10 years, QRS 153 ± 22 ms, 21 (51 %) ischaemic cardiomyopathy, left ventricular (LV) ejection fraction 25 ± 7 %), who successfully underwent temporary stimulation with pacing leads in the RV apex (RV_apex) and left ventricular posterolateral (PL) wall were included. Stroke work, assessed by a conductance catheter, was used to assess acute haemodynamic response during baseline conditions and RV_apex, PL (LV) and PL+RV_apex (BiV) stimulation.

Compared with baseline, stroke work improved similarly during LV and BiV stimulation (∆+ 51 ± 42 % and ∆+ 48 ± 47 %, both p < 0.001), but individual response showed substantial differences between LV and BiV stimulation. Multivariate analysis revealed that RV ejection fraction (β = 1.01, p = 0.02) was an independent predictor for stroke work response during LV stimulation, but not for BiV stimulation. Other parameters, including atrioventricular delay and scar presence and localisation, did not predict stroke work response in CRT.

Conclusion

The haemodynamic effect of addition of RV_apex stimulation to LV stimulation differs widely among patients receiving CRT. Poor RV function is associated with poor response to LV but not BiV stimulation.

Electronic supplementary material

The online version of this article (doi:10.1007/s12471-015-0770-x) contains supplementary material, which is available to authorized users.

Atrial synchronous left ventricular only pacing with VDD pacemaker system - a cost effective alternative to conventional cardiac resynchronization therapy

INTRODUCTION

Atrial synchronous left ventricular (LV) only pacing using two leads and VDD pacemaker could be a cost effective alternative to conventional cardiac resynchronization therapy (CRT).

METHODS

We implanted right atrial (RA) and LV leads with VDD pulse generator (LV only pacing) in five carefully screened heart failure patients who could not afford conventional CRT. All had NYHA class III/IV symptoms despite maximal guideline directed medical therapy. The sensed atrioventricular delay was programmed to pre-excite the LV and achieve fusion beat. Response to treatment was assessed at 6 months.

RESULTS

Four patients were males. The mean age was 58 ± 12 years. At follow up, there was improvement in electrocardiographic, and echocardiographic parameters: Mean QRS duration decreased from 174 ± 17 msec to 128 ± 10.9 msec (p = 0.009), LV end-diastolic diameter decreased from 73.2 ± 12 mm to 65.8 ± 9.6 mm (p = 0.026), LV end-systolic diameter decreased from 65 ± 12 mm to 54 ± 10 mm (p = 0.020). There was a trend towards reduction of LV end-systolic and end-diastolic volumes. LV ejection fraction improved from 25 ± 6% to 34 ± 6% (p = 0.013) and left atrial dimension reduced from 44 ± 4 mm to 39 ± 5 mm (p = 0.045). All patients improved clinically.

CONCLUSION

RA-LV pacing using VDD pacemaker is a safe and effective technique of CRT. This may be a cost effective alternative to conventional CRT for patients in developing countries.

Impact of pacing site on QRS duration and its relationship to hemodynamic response in cardiac resynchronization therapy for congestive heart failure

INTRODUCTION

Recent studies have demonstrated that left ventricular (LV) pacing site is a critical parameter in optimizing cardiac resynchronization therapy (CRT). The present study evaluates the effect of pacing from different LV locations on QRS duration (QRSd) and their relationship to acute hemodynamic response in congestive heart failure patients.

METHODS AND RESULTS

Thirty-five patients with nonischemic dilated cardiomyopathy and left bundle branch block referred for CRT device implantation were studied. Eleven predetermined LV pacing sites were systematically assessed in random order: epicardial: coronary sinus (CS); endocardial: basal and mid-cavity (septal, anterior, lateral, and inferior), apex, and the endocardial site facing the CS pacing site. For each patient QRSd and +dP/dtmax during baseline (AAI) and DDD LV pacing at 2 atrioventricular delays were compared. Response to CRT was significantly better in patients with wider baseline QRSd (≥150 milliseconds). Hemodynamic response was inversely correlated to increase of QRSd during LV pacing (short atrioventricular [AV] delay: r = 0.44, P < 0.001; long AV delay: r = 0.59, P < 0.001). Compared to baseline, LV pacing at the site of shortest QRSd significantly improved +dP/dtmax (+18 ± 25%, P < 0.001) but was not superior to other conventional strategy (lateral wall, CS pacing, and echo-guided) and was inferior to a hemodynamically guided strategy.

CONCLUSIONS

In our study, we have demonstrated that changes of QRSd during LV pacing correlated with acute hemodynamic response and that LV pacing location was a primary determinant of paced QRSd. Although QRSd did not predict the maximum hemodynamic response, our results confirm the link between electrical activation and hemodynamic response of the LV during CRT.

Delayed trans-septal activation results in comparable hemodynamic effect of left ventricular and biventricular endocardial pacing: insights from electroanatomical mapping

BACKGROUND

We sought to compare left ventricular (LVepi) and biventricular epicardial pacing (BIVepi) with LV (LVendo) and BIV endocardial pacing (BIVendo) in patients with chronic heart failure with an emphasis on the underlying electrophysiological mechanisms and hemodynamic effects.

METHODS AND RESULTS

Ten patients with chronically implanted cardiac resynchronization devices underwent temporary LVendo and BIVendo pacing with an LV endocardial roving catheter. A pressure wire and noncontact mapping array were placed to the LV cavity to measure LVdP/dtmax and perform electroanatomical mapping. At the optimal endocardial position, the acute hemodynamic response (AHR) was superior to epicardial stimulation, the AHR to BIVendo pacing and LVendo pacing being comparable (21±15% versus 22±17%; P=NS). During intrinsic conduction, QRS duration was 185±30 ms, endocardial LV total activation time 92±27 ms, and trans-septal activation time 60±21 ms. With LVendo pacing, QRS duration (187±29 ms; P=NS) and endocardial LV total activation time (91±23 ms; P=NS) were comparable with intrinsic conduction. There was no significant difference in endocardial LV total activation time between LVendo and BIVendo pacing (91±23 versus 85±15 ms; P=NS). Assessment of isochronal maps identified slow trans-septal conduction with both LVendo and BIVendo pacing resulting in activation of almost the entire LV endocardium prior to septal breakout, thereby limiting any possible fusion with either pacing mode.

CONCLUSIONS

The equivalent AHR to LVendo and BIVendo pacing may be explained by prolonged trans-septal conduction limiting fusion of electrical wavefronts. The optimal AHR was associated with predominantly LV pre-excitation and depolarization. Our results suggest that LV pacing alone may offer a viable endocardial stimulation strategy to achieve cardiac resynchronization.

Deterioration of left ventricular ejection fraction and contraction synchrony during right ventricular pacing in patients with left bundle branch block

BACKGROUND

Electrocardiographic left bundle branch block (LBBB) may be intrinsic, due to ventricular conduction system disease, or induced by right ventricular pacing. Prior reports clearly delineate the derogatory impact of LBBB on left ventricular (LV) mechanical synchrony and global function, and suggest that the intrinsic and induced varieties are equivalent. This study sought to determine the difference in LV synchrony and global function between intrinsic LBBB and right ventricular apical pacing induced LBBB.

METHODS

Ten patients with heart failure, diminished ejection fraction (EF) (33 ± 11%), intrinsic LBBB and an implanted cardiac pacing device were studied. In each patient, separate gated SPECT acquisitions were performed during intrinsic ventricular activation (atrial pacing) and during induced LBBB (atrial and right ventricular pacing). During each condition, LVEF, contraction synchrony (phase standard deviation, PSD), and spatial pattern of activation were measured.

RESULTS

Compared to intrinsic, induced LBBB was associated with decreased EF (30 ± 11% vs 33 ± 11%, P = .007), contraction synchrony (PSD 49.7 ± 23.2° vs 41.6 ± 19.8, P = .02), and a disparate spatial pattern of activation.

CONCLUSIONS

Induced LBBB is associated with significantly worse global and regional LV mechanical function than intrinsic LBBB.

Left ventricular synchrony and function in pediatric patients with definitive pacemakers

BACKGROUND

Chronic right ventricular pacing (RVP) induces a dyssynchronous contraction pattern,producing interventricular and intraventricular asynchrony. Many studies have shown the relationship of RVP with impaired left ventricular (LV) form and function.

OBJECTIVE

The aim of this study was to evaluate LV synchrony and function in pediatric patients receiving RVP in comparison with those receiving LV pacing (LVP).

METHODS

LV systolic and diastolic function and synchrony were evaluated in 80 pediatric patients with either nonsurgical or postsurgical complete atrioventricular block, with pacing from either the RV endocardium (n = 40) or the LV epicardium (n = 40). Echocardiographic data obtained before pacemaker implantation, immediately after it, and at the end of a mean follow-up of 6.8 years were analyzed.

RESULTS

LV diastolic function did not change in any patient during follow-up. LV systolic function was preserved in patients with LVP. However, in children with RVP the shortening fraction and ejection fraction decreased from medians of 41% ± 2.6% and 70% ± 6.9% before implantation to 32% ± 4.2% and 64% ± 2.5% (p < 0.0001 and p < 0.0001), respectively, at final follow-up. Interventricular mechanical delay was significantly larger with RVP (66 ± 13 ms) than with LVP (20 ± 8 ms). Similarly, the following parameters were significantly different in the two groups: LV mechanical delay (RVP: 69 ± 6 ms, LVP: 30 ± 11 ms, p < 0.0001); septal to lateral wall motion delay (RVP: 75 ± 19 ms, LVP: 42 ± 10 ms, p < 0.0001); and, septal to posterior wall motion delay (RVP: 127 ± 33 ms, LVP: 58 ± 17 ms, p < 0.0001).

CONCLUSION

Compared with RV endocardium, LV epicardium is an optimal site for pacing to preserve cardiac synchrony and function.

Cardiac resynchronization therapy modulation of exercise left ventricular function and pulmonary O₂ uptake in heart failure

To better understand the mechanisms contributing to improved exercise capacity with cardiac resynchronization therapy (CRT), we studied the effects of 6 mo of CRT on pulmonary O(2) uptake (Vo(2)) kinetics, exercise left ventricular (LV) function, and peak Vo(2) in 12 subjects (age: 56 ± 15 yr, peak Vo(2): 12.9 ± 3.2 ml·kg(-1)·min(-1), ejection fraction: 18 ± 3%) with heart failure. We hypothesized that CRT would speed Vo(2) kinetics due to an increase in stroke volume secondary to a reduction in LV end-systolic volume (ESV) and that the increase in peak Vo(2) would be related to an increase in cardiac output reserve. We found that Vo(2) kinetics were faster during the transition to moderate-intensity exercise after CRT (pre-CRT: 69 ± 21 s vs. post-CRT: 54 ± 17 s, P < 0.05). During moderate-intensity exercise, LV ESV reserve (exercise - resting) increased 9 ± 7 ml (vs. a 3 ± 9-ml decrease pre-CRT, P < 0.05), and steady-state stroke volume increased (pre-CRT: 42 ± 8 ml vs. post-CRT: 61 ± 12 ml, P < 0.05). LV end-diastolic volume did not change from rest to steady-state exercise post-CRT (P > 0.05). CRT improved heart rate, measured as a lower resting and steady-state exercise heart rate and as faster heart rate kinetics after CRT (pre-CRT: 89 ± 12 s vs. post-CRT: 69 ± 21 s, P < 0.05). For peak exercise, cardiac output reserve increased significantly post-CRT and was 22% higher at peak exercise post-CRT (both P < 0.05). The increase in cardiac output was due to both a significant increase in peak and reserve stroke volume and to a nonsignificant increase in heart rate reserve. Similar patterns in LV volumes as moderate-intensity exercise were observed at peak exercise. Cardiac output reserve was related to peak Vo(2) (r = 0.48, P < 0.05). These findings demonstrate the chronic CRT-mediated cardiac factors that contribute, in part, to the speeding in Vo(2) kinetics and increase in peak Vo(2) in clinically stable heart failure patients.

Left Ventricular Versus Simultaneous Biventricular Pacing in Patients With Heart Failure and a QRS Complex ≥120 Milliseconds

Background—

Left ventricular (LV) pacing alone may theoretically avoid deleterious effects of right ventricular pacing.

Methods and Results—

In a multicenter, double-blind, crossover trial, we compared the effects of LV and biventricular (BiV) pacing on exercise tolerance and LV remodeling in patients with an LV ejection fraction ≤35%, QRS ≥120 milliseconds, and symptoms of heart failure. A total of 211 patients were recruited from 11 centers. After a run-in period of 2 to 8 weeks, 121 qualifying patients were randomized to LV followed by BiV pacing or vice versa for consecutive 6-month periods. The greatest improvement in New York Heart Association class and 6-minute walk test occurred during the run-in phase before randomization. Exercise duration at 75% of peak V o 2 (primary outcome) increased from 9.3±6.4 to 14.0±11.9 and 14.3±12.5 minutes with LV and BiV pacing, respectively, with no difference between groups ( P =0.4327). LV ejection fraction improved from 24.4±6.3% to 31.9±10.8% and 30.9±9.8% with LV and BiV pacing, respectively, with no difference between groups ( P =0.4530). Reductions in LV end-systolic volume were likewise similar ( P =0.6788). The proportion of clinical responders (≥20% increase in exercise duration) to LV and BiV pacing was 48.0% and 55.1% ( P =0.1615). Positive remodeling responses (≥15% reduction in LV end-systolic volume) were observed in 46.7% and 55.4% ( P =0.0881). Overall, 30.6% of LV nonresponders improved with BiV and 17.1% of BiV nonresponders improved with LV pacing.

Conclusion—

LV pacing is not superior to BiV pacing. However, nonresponders to BiV pacing may respond favorably to LV pacing, suggesting a potential role as tiered therapy.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00901212.

Meta-analysis of randomized controlled trials comparing isolated left ventricular and biventricular pacing in patients with chronic heart failure

Cardiac resynchronization therapy (CRT) has been mostly achieved by biventricular pacing (BVP) in patients with chronic heart failure (CHF), although it can also be provided by left ventricular pacing (LVP). The superiority of BVP over LVP remains uncertain. The present meta-analysis of randomized controlled trials was performed to compare the effects of LVP to BVP in patients with CHF. Outcomes analyzed included clinical status (6-minute walk distance, peak oxygen consumption, quality of life, New York Heart Association class), LV function (LV ejection fraction), and LV remodeling (LV end-systolic volume). Five trials fulfilled criteria for inclusion in analysis, which included 574 patients with CHF indicated for CRT. After a midterm follow-up, pooled analysis demonstrated that LVP resulted in similar improvements in 6-minute walk distance (weighted mean difference [WMD] 11.25, 95% confidence interval [CI] -12.39 to 34.90, p = 0.35), quality of life (WMD 0.34, 95% CI -3.72 to 4.39, p = 0.87), peak oxygen consumption (WMD 1.00, 95% CI -0.84 to 2.85, p = 0.29), and New York Heart Association class (WMD -0.19, 95% CI -0.79 to 0.42, p = 0.54). There was a trend toward a superiority of BVP over LVP for LV ejection fraction (WMD 1.28, 95% CI -0.11 to 2.68, p = 0.07) and LV end-systolic volume (WMD -5.73, 95% CI -11.86 to 0.39, p = 0.07). In conclusion, LVP achieves similar improvement in clinical status as BVP in patients with CHF, whereas there was a trend toward superiority of BVP over LVP for LV reverse modeling and systolic function.

Long-term follow-up of cardiac resynchronization therapy: mechanical resynchronization and reverse left ventricular remodeling are predictive for long-term transplant-free survival

We sought to determine whether correction of mechanical left ventricular (LV) dyssynchrony as defined by tissue Doppler imaging (TDI) is predictive for transplant-free long-term survival in patients (pts.) undergoing cardiac resynchronization therapy (CRT). In 76 CRT recipients TDI curves from the septal, lateral, anterior, and inferior basal LV were obtained at baseline and after 6 ± 4 months. A time difference between regional electromechanical delays (EMD) of ≥40 ms was considered dyssynchronous. At follow-up, pts. were classified as TDI-responders (TDI-R: dyssynchrony at baseline, corrected by CRT) versus non-responders (TDI-NR: either not dyssynchronous at baseline, or persisting dyssynchrony). Pts. were then followed by standard echocardiography over 21 ± 6 months and were re-classified as LV remodelers (LV-R: LV volume reduction of >10%) versus non-remodelers (LV-NR). The end-point during clinical long-term follow-up of 65 ± 38 months was all-cause mortality or heart transplantation. 44 out of the 76 pts. (58%) were classified as TDI-R, 32 (42%) as TDI-NR. Significant reverse LV remodeling was observed in 41 (54%) pts., while 35 (46%) did not improve LV size and function. TDI-R was associated with LV-R in 35 pts. (85%; P < 0.001). During long-term follow-up, 38 pts. (50%) reached the end point, 11 (30%) in the TDI-R group, and 27 (70%) in the TDI-NR group (P < 0.0003). Mechanical resynchronization as defined by TDI translates into a significant survival benefit in CRT recipients.

Chronic ventricular pacing in children: toward prevention of pacing-induced heart disease

In children with congenital or acquired complete atrioventricular (AV) block, ventricular pacing is indicated to increase heart rate. Ventricular pacing is highly beneficial in these patients, but an important side effect is that it induces abnormal electrical activation patterns. Traditionally, ventricular pacemaker leads are positioned at the right ventricle (RV). The dyssynchronous pattern of ventricular activation due to RV pacing is associated with an acute and chronic impairment of left ventricular (LV) function, structural remodeling of the LV, and increased risk of heart failure. Since the degree of pacing-induced dyssynchrony varies between the different pacing sites, ‘optimal-site pacing’ should aim at the prevention of mechanical dyssynchrony. Especially in children, generally paced from a very early age and having a perspective of life-long pacing, the preservation of cardiac function during chronic ventricular pacing should take high priority. In the perspective of the (patho)physiology of ventricular pacing and the importance of the sequence of activation, this paper provides an overview of the current knowledge regarding possible alternative sites for chronic ventricular pacing. Furthermore, clinical implications and practical concerns of the various pacing sites are discussed. The review concludes with recommendations for optimal-site pacing in children.

Pivotal trials of cardiac resynchronization therapy: evolution to therapy in mild heart failure

Cardiac resynchronization therapy (CRT) has traditionally been reserved for patients with left ventricular (LV) dysfunction in the setting of advanced heart failure. Early clinical trials clearly demonstrated reverse ventricular remodeling and clinical benefits following CRT in this population. More recently, with the publication of the REVERSE, MADIT-CRT, and RAFT trials, the benefits of CRT have been demonstrated in patients with LV dysfunction and mild heart failure calling into question the optimal timing for biventricular pacemaker implantation. With the expanded indications for CRT arising from these studies, significant questions remain specifically with regards to the economic impact on health care systems and to the added risk of future morbidity due to device infection and malfunction.

Pacing within the ischemic area significantly decreases the left ventricular ejection fraction during experimental acute myocardial infarction

BACKGROUND

The aim of this study was to examine the effects on left ventricular (LV) function of LV apical or/and lateral wall pacing during an experimental acute myocardial infarction.

METHODS

In 12 anesthetized pigs, epicardial LV pacing at the apex or lateral wall, or at both sites simultaneously, was performed before and after left anterior descending (LAD) ligation. Data concerning LV function were obtained by two-dimensional echo during spontaneous sinus rhythm (SR) and during pacing before and 15, 45, 60, and 90 minutes after LAD ligation.

RESULTS

Before ligation of the LAD, pacing at the lateral wall (48.04 ± 6.25%) or both sites (45.71 ± 6.31%) reduced the LV ejection fraction (EF) significantly (P < 0.01) in comparison to SR (55.44 ± 4.10%). However, during pacing at the apex (50.19 ± 6.50%), the reduction was not significant. After LAD ligation, the EF during lateral pacing (43.02 ± 7.71%) was significantly higher than during apical pacing (38.78 ± 8.26%, P < 0.04) but was not significantly different from that during dual-site pacing (41.65 ± 8.69%).

CONCLUSIONS

Pacing within the ischemic LV apical zone after LAD ligation impairs left ventricular ejection fraction, as compared with pacing the nonischemic LV lateral wall, and should therefore be avoided in clinical settings where the LV pacing site may be chosen.

Isolated left ventricular pacing results in worse long-term clinical outcome when compared with biventricular pacing: a single-centre randomized study

AIMS

The objective of this study was to compare long-term clinical effects of biventricular pacing with isolated left ventricular pacing.

METHODS AND RESULTS

Forty consecutive patients with idiopathic dilated cardiomyopathy and indication for cardiac resynchronization therapy were randomized to biventricular or isolated left ventricular pacing. Clinical and echocardiographic parameters were studied regularly prior to implantation and during 1 year of follow-up. Patients with atrial fibrillation were excluded from the study. A retrospective cross-sectional outcome analysis was performed 4 years after the beginning of the study. Biventricular pacing was associated with more pronounced clinical and echocardiographic benefit compared with left ventricular pacing. Biventricular pacing was associated with significantly more distinct reverse remodelling. Left ventricular ejection fraction improved by 12.5 per cent-points (95% CI 7.3-17.7) compared with 5.1 per cent-points (95% CI 1.1-9.2) (P = 0.01) and left ventricular end-diastolic diameter decreased by 8.69 mm (95% CI 5.2-12.2) compared with 5.1 mm (95% CI 1.5-8.7) (P = 0.05) in the biventricular and left-ventricular pacing group, respectively. Semi-quantitative summarization of response points revealed a greater benefit in the biventricular vs. left ventricular pacing group [mean sum of response points 3.25 (95% CI 2.62-3.88) vs. 2.35 (95% CI 1.74-2.96), respectively, P = 0.06]. After 3 years of follow-up, there was no cardiovascular death in the biventricular pacing group compared with three cardiovascular deaths in the left ventricular pacing group.

CONCLUSION

In patients with idiopathic dilated cardiomyopathy, biventricular pacing is associated with significantly more pronounced benefit in clinical outcomes and reverse remodelling. A retrospective analysis after 3 years of follow-up suggests that isolated left ventricular pacing may be associated with a higher mortality rate compared with biventricular pacing.

A randomized double-blind comparison of biventricular versus left ventricular stimulation for cardiac resynchronization therapy: the Biventricular versus Left Univentricular Pacing with ICD Back-up in Heart Failure Patients (B-LEFT HF) trial

BACKGROUND

Biventricular (BiV) stimulation is the preferred means of delivering cardiac resynchronization therapy (CRT), although left ventricular (LV)-only stimulation might be as safe and effective. B-LEFT HF is a prospective, multicenter, randomized, double-blind study aimed to examine whether LV-only is noninferior to BiV pacing regarding clinical and echocardiographic responses.

METHODS

B-LEFT HF randomly assigned 176 CRT-D recipients, in New York Heart Association class III or IV, with an LV ejection fraction < or =35% and QRS > or =130 milliseconds, to a BiV (n = 90) versus LV (n = 86) stimulation group. Clinical status and echocardiograms were analyzed at baseline and 6 months after CRT-D implant to test the noninferiority of LV-only compared with BiV stimulation.

RESULTS

The proportion of responders was in line with current literature on CRT, with improvement in heart failure composite score in 76.2% and 74.7% of patients in BiV and LV groups, respectively. Comparing LV versus BiV pacing, the small differences in response rates and corresponding 95% CI indicated that LV pacing was noninferior to BiV pacing for a series of response criteria (combination of improvement in New York Heart Association and reverse remodeling, improvement in heart failure composite score, reduction in LV end-systolic volume of at least 10%), both at intention-to-treat and at per-protocol analysis.

CONCLUSIONS

Left ventricular-only pacing is noninferior to BiV pacing in a 6-month follow-up with regard to clinical and echocardiographic responses. Left ventricular pacing may be considered as a clinical alternative option to BiV pacing.

Dynamic and site-specific impact of ventricular pacing on left ventricular ejection fraction

BACKGROUND

Some studies suggest that right ventricular (RV) pacing has an adverse impact on left ventricular ejection fraction (LVEF), particularly in subjects with preexisting left ventricular (LV) dysfunction, and that direct LV pacing may be relatively protective. Interactions between pacing site and LVEF remain unclear.

OBJECTIVE

The purpose of this study was to examine the relative impact of RV and LV pacing on LVEF by serial study during a period in which LV dysfunction, induced by tachypacing, was introduced and then resolved.

METHODS

In each of five dogs, RV, LV, and simultaneous RV and LV (BiV) pacing modes were compared to native ventricular activation (1) prior to tachypacing (baseline), (2) weekly during a 5-week continuous tachypacing period, and (3) weekly during a 3-week post-tachypacing recovery period. At each evaluation, LVEF and LV contraction synchrony were assessed during each pacing mode.

RESULTS

The decrease in LVEF during the tachypacing period was more pronounced during RV pacing than during native activation or LV or BiV pacing. The magnitude of this effect correlated with a diminishment in LV contraction synchrony that was not observed during native activation or LV or BiV pacing. During the post-tachypacing period, gradual reversal of these changes toward baseline was observed.

CONCLUSION

Compared to native activation, RV pacing worsens LVEF in a manner proportional to the severity of preexisting LV dysfunction, attributable to reduced LV contraction synchrony. In comparison, both LV and BiV pacing preserve LVEF and contraction synchrony.

Optimizing hemodynamics in heart failure patients by systematic screening of left ventricular pacing sites: the lateral left ventricular wall and the coronary sinus are rarely the best sites

OBJECTIVES

We sought to evaluate the impact of the left ventricular (LV) pacing site on hemodynamic response to cardiac resynchronization therapy (CRT).

BACKGROUND

CRT reduces morbidity and mortality in heart failure patients. However, 20% to 40% of eligible patients may not fully benefit from CRT device implantation. We hypothesized that selecting the optimal LV pacing site could be critical in this issue.

METHODS

Thirty-five patients with nonischemic dilated cardiomyopathy referred for CRT device implantation were studied. Intraventricular dyssynchrony and latest activated LV wall were defined by tissue Doppler imaging analysis before the study. Eleven predetermined LV pacing sites were systematically assessed in random order: basal and mid-cavity (septal, anterior, lateral, inferior), apex, coronary sinus (CS), and the endocardial site facing the CS pacing site. For each patient, +dP/dT(max), -dP/dT(min), pulse pressure, and end-systolic pressure during baseline (AAI) and DDD LV pacing were compared. Two atrioventricular delays were tested.

RESULTS

Major interindividual and intraindividual variations of hemodynamic response depending on the LV pacing site were observed. Compared with baseline, LV DDD pacing at the best LV position significantly improved +dP/dT(max) (+31 +/- 26%, p < 0.001) and was superior to pacing the CS (+15 +/- 23%, p < 0.001), the lateral LV wall (+18 +/- 22%, p < 0.001), or the latest activated LV wall (+11 +/- 17%, p < 0.001).

CONCLUSIONS

The pacing site is a primary determinant of the hemodynamic response to LV pacing in patients with nonischemic dilated cardiomyopathy. Pacing at the best LV site is associated acutely with fewer nonresponders and twice the improvement in +dP/dT(max) observed with CS pacing.

Cardiac resynchronization therapy: back to ECG?

In recent years, considerable effort has been devoted to improving patient selection and the programming of cardiac resynchronization therapy (CRT). Mechanical dyssynchrony has been investigated through echocardiography and the reliability of ECG in selecting patients has been criticized and doubt has been cast on its role. Up to now, patient selection for CRT has relied upon the criteria of a prolonged QRS, evidence of the electrical impairment of the conduction system. Can we get more information from ECG morphology? Can it provide any marker for selecting candidates to CRT? Can we obtain useful information from the paced ECG morphology by analysis of fusion beats? Can we use ECG to optimize biventricular or single-site left ventricular pacing programming? The present review provides a critical analysis of the criteria for patient selection and the methods for optimal device setting, all based on 12-lead ECG morphology.

Pacing features that mimic malfunction: a review of current programmable and automated device functions that cause confusion in the clinical setting

Modern implantable devices capable of pacing are armed with a multitude of programmable and automated features. While some features represent important advances in device safety and performance, many can also mimic device malfunction. This article discusses these features in terms of the confusion they may cause and highlights important clinical clues that aid in their recognition.

Effect of biventricular pacing during a ventricular sensed event

Loss of biventricular (BiV) pacing occurs during ventricular sensed events such as frequent ventricular ectopy, nonsustained ventricular tachycardia, and intrinsic atrioventricular nodal conduction, such as in atrial fibrillation. Ventricular sense response (VSR) pacing, a novel cardiac resynchronization therapy pacing strategy, maintains BiV pacing during these sensed ventricular events. Patients who underwent echocardiographic optimization after BiV pacemaker implantation were enrolled, and aortic velocity-time integrals (VTIs) were recorded and compared during intrinsic conduction without pacing, optimized BiV pacing, and intrinsic conduction with VSR pacing alone. Thirty-two patients were enrolled (mean age 68 +/- 11 years, 78% men), with a mean baseline QRS duration of 164 +/- 24 ms and a mean left ventricular ejection fraction of 23 +/- 10%. The mean aortic VTI during intrinsic conduction with VSR pacing was 16.5 +/- 3.6 cm, compared with 15.3 +/- 3.4 cm during intrinsic conduction without pacing (p <0.001). The mean aortic VTI with optimized BiV pacing was 17.3 +/- 3.6 cm, significantly better (p <0.001) compared with intrinsic conduction without pacing. Improvements in aortic VTI were higher with optimized BiV pacing compared with VSR pacing alone (p = 0.02). In the subgroup of patients with left bundle branch block-type activation, the hemodynamic improvements realized with VSR pacing were similar to optimized BiV pacing. Mean aortic VTI improvements with VSR were similar in patients with ischemic and nonischemic cardiomyopathy. In conclusion, a cardiac resynchronization therapy algorithm that maintains BiV pacing during a ventricular sensed event appears to have an aortic VTI response that is significantly better compared with intrinsic conduction without pacing.

Effect of right ventricular pacing lead on left ventricular dyssynchrony in patients receiving cardiac resynchronization therapy

Right ventricular (RV) pacing-induced left ventricular (LV) dyssynchrony can be 1 reason of nonresponse to cardiac resynchronization therapy (CRT) by potentially interfering with spontaneous dyssynchrony. We investigated the effect of the RV pacing lead on LV dyssynchrony in patients receiving CRT. LV radial dyssynchrony was assessed in a 16-segment model by using the novel speckle-tracking imaging before CRT and after the procedure, when the device was randomized to biventricular and RV pacing with crossover after 48 hours. LV lead tip was localized under fluoroscopic guidance. Of 43 patients, 30 (70%) acutely responded to CRT by a decrease in end-systolic volume >10%. RV pacing did not significantly increase the magnitude but altered the pattern of intraventricular dyssynchrony in the overall study group. During RV pacing, major shifts in the latest activated region occurred in 20 patients. However, LV radial dyssynchrony during spontaneous rhythm, but not the 1 induced by RV pacing, predicted response to CRT. When lead localization was optimal according to spontaneous dyssynchrony, response rate was 89% compared with 50% when lead localization was not optimal (p = 0.01). In contrast, when lead localization was optimal according to RV pacing-induced dyssynchrony, response rate was 81% compared with 67% when lead localization was not optimal (p = NS). In conclusion, RV apical pacing can alter the pattern of spontaneous LV dyssynchrony in patients receiving CRT. However, this alteration does not detract from the value of assessing LV dyssynchrony during spontaneous rhythm to predict responders to CRT.

Chronic left ventricular pacing preserves left ventricular function in children

Chronic right ventricular (RV) pacing can induce structural and functional cardiac deterioration. Because animal studies showed a benefit of left ventricular (LV) over RV pacing, this study compared the effects of chronic RV and LV pacing in children. Retrospectively, echocardiographic data were evaluated from 18 healthy children (control subjects) and from children undergoing chronic epicardial RV pacing (7 RVP) or LV pacing (7 LVP). Assessment included LV end-diastolic wall thickness (LVEDWT) and end-systolic wall thickness (LVESWT) as well as LV end-diastolic diameter (LVEDD) and end-systolic diameter (LVESD). The shortening fraction and eccentricity index (LV diameter/2xLV wall thickness) were calculated as measures of LV function and eccentricity, respectively. Duration of QRS and septal posterior wall motion delay (SPWMD) were used as measures of electrical and mechanical dyssynchrony, respectively. A p value less than 0.05 determined significance. As the findings showed, LVEDD, LVESD, LVEDWT, and LVESWT were not significantly different between the groups. The shortening fraction was significantly lower in the RVP (21.7%+/-6.0%) than in the LVP (32.2%+/-5.2%) or control (29.3%+/-4.3%) children. The systolic LV eccentricity index was significantly larger in the RVP (1.8+/-0.2) than in the LVP (1.4+/-0.1) or control (1.4+/-0.2) children. The SPWMD was significantly larger in the RVP (338+/-20 ms) than in the LVP (-16+/-14 ms) or control (-5+/-35 ms) group, whereas QRS duration was similarly longer in the RVP (157+/-10 ms) and LVP (158+/-22 ms) groups compared than in the control group (69+/-7 ms). The authors conclude that LV function in children is preserved by chronic pacing at the LV lateral wall.

Myocardial scintigraphy after pacemaker implantation for congenital complete atrioventricular block

Patients with isolated congenital complete atrioventricular block (CCAVB) occasionally develop dilated cardiomyopathy (DCM), despite early pacemaker implantation. However, the etiology of the DCM and its relationship to permanent ventricular pacing are not fully understood. Twenty-five patients with CCAVB underwent (99m) technetium (Tc) myocardial perfusion scintigraphy. Five patients were studied before and after pacing, providing a total of 30 image sets, which were divided into three groups; group 1: CCAVB before pacemaker implantation (PMI) (n = 11); group 2: CCAVB after PMI who did not subsequently develop DCM (n = 13); group 3: CCAVB after PMI who subsequently developed DCM (n = 6). Perfusion defects on single-photon-emission computed tomography (SPECT) were identified in group 1, 0 of 11 patients; group 2, 85% of patients; and group 3, 100% of patients. In groups 2 and 3, in patients with right ventricular pacing, the perfusion defects were mainly in the septum or between the apex and septum. On 20 segments' polar maps, the distribution of %uptake showed a similar pattern in groups 2 and 3, the degree of decreased %uptake and the number of segments with decreased %uptake being more severe in group 3. "Artificial" left bundle branch block (LBBB) pattern myocardial contraction induced by right ventricular pacing decreased myocardial perfusion around the apex and septum. Some patients with CCAVB will develop left ventricular dysfunction caused by artificial LBBB-induced interventricular asynchrony.

Fusion beat in patients with heart failure treated with left ventricular pacing: may ECG morphology relate to mechanical synchrony? A pilot study

BACKGROUND

Electrical fusion between left ventricular pacing and spontaneous right ventricular activation is considered the key to resynchronisation in sinus rhythm patients treated with single-site left ventricular pacing.

AIM

Use of QRS morphology to optimize device programming in patients with heart failure (HF), sinus rhythm (SR), left bundle branch block (LBBB), treated with single-site left ventricular pacing.

METHODS AND RESULTS

We defined the "fusion band" (FB) as the range of AV intervals within which surface ECG showed an intermediate morphology between the native LBBB and the fully paced right bundle branch block patterns.Twenty-four patients were enrolled. Echo-derived parameters were collected in the FB and compared with the basal LBBB condition. Velocity time integral and ejection time did not improve significantly. Diastolic filling time, ejection fraction and myocardial performance index showed a statistically significant improvement in the FB. Interventricular delay and mitral regurgitation progressively and significantly decreased as AV delay shortened in the FB. The tissue Doppler asynchrony index (Ts-SD-12-ejection) showed a non significant decreasing trend in the FB. The indications provided by the tested parameters were mostly concordant in that part of the FB corresponding to the shortest AV intervals.

CONCLUSION

Using ECG criteria based on the FB may constitute an attractive option for a safe, simple and rapid optimization of resynchronization therapy in patients with HF, SR and LBBB.

Diminished left ventricular dyssynchrony and impact of resynchronization in failing hearts with right versus left bundle branch block

OBJECTIVES

We compared mechanical dyssynchrony and the impact of cardiac resynchronization therapy (CRT) in failing hearts with a pure right (RBBB) versus left bundle branch block (LBBB).

BACKGROUND

Cardiac resynchronization therapy is effective for treating failing hearts with conduction delay and discoordinate contraction. Most data pertain to LBBB delays. With RBBB, the lateral wall contracts early so that biventricular (BiV) pre-excitation may not be needed. Furthermore, the magnitude of dyssynchrony and impact of CRT in pure RBBB versus LBBB remains largely unknown.

METHODS

Dogs with tachypacing-induced heart failure combined with right or left bundle branch radiofrequency ablation were studied. Basal dyssynchrony and effects of single and BiV CRT on left ventricular (LV) function were assessed by pressure-volume catheter and tagged magnetic resonance imaging, respectively.

RESULTS

Left bundle branch block and RBBB induced similar QRS widening, and LV function (ejection fraction, maximum time derivative of LV pressure [dP/dt(max)]) was similarly depressed in failing hearts with both conduction delays. Despite this, mechanical dyssynchrony was less in RBBB (circumferential uniformity ratio estimate [CURE] index: 0.80 +/- 0.03 vs. 0.58 +/- 0.09 for LBBB, p < 0.04; CURE 0-->1 is dyssynchronous-->synchronous). Cardiac resynchronization therapy had correspondingly less effect on hearts with RBBB than those with LBBB (i.e., 5.5 +/- 1.1% vs. 29.5 +/- 5.0% increase in dP/dt(max), p < 0.005), despite similar baselines. Furthermore, right ventricular-only pacing enhanced function and synchrony in RBBB as well or better than did BiV, whereas LV-only pacing worsened function.

CONCLUSIONS

Less mechanical dyssynchrony is induced by RBBB than LBBB in failing hearts, and the corresponding impact of CRT on the former is reduced. Right ventricular-only pacing may be equally efficacious as BiV CRT in hearts with pure right bundle branch conduction delay.

Avoidance of Right Ventricular Pacing in Cardiac Resynchronization Therapy Improves Right Ventricular Hemodynamics in Heart Failure Patients

BACKGROUND

Cardiac resynchronization therapy (CRT) applied by pacing the left and right ventricles (BiV) has been shown to provide synchronous left ventricular (LV) contraction in heart failure patients. CRT may also be accomplished through synchronization of a properly timed LV pacing impulse with intrinsically conducted activation wave fronts. Elimination of right ventricular (RV) pacing may provide a more physiological RV contraction pattern and reduce device current drain. We evaluated the effects of LV and BiV pacing over a range of atrioventricular intervals on the performance of both ventricles.

METHODS

Acute LV and RV hemodynamic data from 17 patients with heart failure (EF = 30 +/- 1%) and a wide QRS (138 +/- 25 msec) or mechanical dyssynchrony were acquired during intrinsic rhythm, BiV, and LV pacing.

RESULTS

The highest LV dP/dt(max) was achieved during LV pre- (LV paced prior to an RV sense) and BiV pacing, followed by that obtained during LV post-pacing (LV paced after an RV sense) and the lowest LV dP/dt(max) was recorded during intrinsic rhythm. Compared with BiV pacing, LV pre-pacing significantly improved RV dP/dt(max) (378 +/- 136 mmHg/second vs 397 +/- 136 mmHg/second, P < 0.05) and preserved RV cycle efficiency (61.6 +/- 14.6% vs 68.6 +/- 11.4%, P < 0.05) and stroke volume (6.6 +/- 4.4 mL vs 9.0 +/- 6.3 mL, P < 0.05). Based on LV dP/dt(max), the optimal atrioventricular interval could be estimated by subtracting 30 msec from the intrinsic atrial to sensed RV interval.

CONCLUSIONS

Synchronized LV pacing produces acute LV and systemic hemodynamic benefits similar to BiV pacing. LV pacing at an appropriate atrioventricular interval prior to the RV sensed impulse provides superior RV hemodynamics compared with BiV pacing.

Reduced Ventricular Volumes and Improved Systolic Function With Cardiac Resynchronization Therapy

Background— Cardiac resynchronization therapy has emerged as an important therapy for advanced systolic heart failure. Among available cardiac resynchronization therapy pacing modes that restore ventricular synchrony, it is uncertain whether simultaneous biventricular (BiV), sequential BiV, or left ventricular (LV) pacing is superior. The Device Evaluation of CONTAK RENEWAL 2 and EASYTRAK 2: Assessment of Safety and Effectiveness in Heart Failure (DECREASE-HF) trial is the first randomized trial comparing these 3 cardiac resynchronization therapy modalities.

Methods and Results— The DECREASE-HF Trial is a multicenter trial in which 306 patients with New York Heart Association class III or IV heart failure, an LV ejection fraction ≤35%, and a QRS duration ≥150 ms were randomized to simultaneous BiV, sequential BiV, or LV pacing. LV volumes and systolic and diastolic function were assessed with echocardiography at baseline, 3 months, and 6 months. All groups had a significant reduction in LV end-systolic and end-diastolic dimensions ( P <0.001). The simultaneous BiV pacing group had the greatest reduction in LV end-systolic dimension ( P =0.007). Stroke volume ( P <0.001) and LV ejection fraction ( P <0.001) improved in all groups with no difference across groups.

Conclusions— Compared with LV pacing, simultaneous BiV pacing was associated with a trend toward greater improvement in LV size. There is little difference between simultaneous BiV pacing and sequential BiV pacing as programmed in this trial.