A prospective, randomized comparison of the acute hemodynamic effects of biventricular and left ventricular pacing with cardiac resynchronization therapy

Pacemaker-induced atrial fibrillation reconsidered-associations with different pacing sites and prevention approaches

The incidence of atrial fibrillation (AF) is significantly higher in patients with pacemakers than in the general population, which could be due to patient characteristics and the diagnostic tool of the pacemaker in detecting atrial high-rate episodes and subclinical AF, but also to the pacemaker itself providing AF-promoting conditions. It is well known that high ventricular pacemaker burden increases the likelihood of AF occurrence. However, the sites of atrial and ventricular pacing may also influence the risk for AF. The conventional sites for atrial and ventricular pacing are in the right atrial appendage and in the right ventricular apex. However, growing evidence suggests that alternative pacing sites may be superior for the prevention of AF. Bachmann bundle pacing, for example, promotes interatrial excitation conduction, resulting in atrial synchronicity and a shorter total atrial activation time, which may be preventive for the occurrence of AF. Moreover, in recent years, new ventricular pacing sites have come into focus with His bundle and left bundle branch pacing. In addition to the hemodynamic and electrophysiological cardiac benefits, these new options may also offer benefits in the prevention of AF. This review provides an overview of pacing-induced AF mechanisms and the association with different pacing sites, as well as approaches for prevention of pacing-induced AF, highlighting different sites and modes of atrial pacing and the newer sites of ventricular pacing.

Acute Hemodynamic Effects of Cardiac Resynchronization Therapy Versus Alternative Pacing Strategies in Patients With Left Ventricular Assist Devices

Background

The hemodynamic effects of cardiac resynchronization therapy in patients with left ventricular assist devices (LVADs) are uncharacterized. We aimed to quantify the hemodynamic effects of different ventricular pacing configurations in patients with LVADs, focusing on short‐term changes in load‐independent right ventricular (RV) contractility.

Methods and Results

Patients with LVADs underwent right heart catheterization during spontaneous respiration without sedation and with pressures recorded at end expiration. Right heart catheterization was performed at different pacemaker configurations (biventricular pacing, left ventricular pacing, RV pacing, and unpaced conduction) in a randomly generated sequence with >3 minutes between configuration change and hemodynamic assessment. The right heart catheterization operator was blinded to the sequence. RV maximal change in pressure over time normalized to instantaneous pressure was calculated from digitized hemodynamic waveforms, consistent with a previously validated protocol. Fifteen patients with LVADs who were in sinus rhythm were included. Load‐independent RV contractility, as assessed by RV maximal change in pressure over time normalized to instantaneous pressure, was higher in biventricular pacing compared with unpaced conduction (15.7±7.6 versus 11.0±4.0 s⁻¹; P=0.003). Thermodilution cardiac output was higher in biventricular pacing compared with unpaced conduction (4.48±0.7 versus 4.38±0.8 L/min; P=0.05). There were no significant differences in heart rate, ventricular filling pressures, or atrioventricular valvular regurgitation across all pacing configurations.

Conclusions

Biventricular pacing acutely improves load‐independent RV contractility in patients with LVADs. Even in these patients with mechanical left ventricular unloading via LVAD who were relative pacing nonresponders (required LVAD support despite cardiac resynchronization therapy), biventricular pacing was acutely beneficial to RV contractility.

Effect of Interventricular Electrical Delay on Atrioventricular Optimization for Cardiac Resynchronization Therapy

BACKGROUND

Routine atrioventricular optimization (AVO) has not been shown to improve outcomes with cardiac resynchronization therapy (CRT). However, more recently subgroup analyses of multicenter CRT trials have identified electrocardiographic or lead positions associated with benefit from AVO. Therefore, the purpose of this analysis was to evaluate whether interventricular electrical delay modifies the impact of AVO on reverse remodeling with CRT.

METHODS

This substudy of the SMART-AV trial (SMARTDELAY Determined AV Optimization) included 275 subjects who were randomized to either an electrogram-based AVO (SmartDelay) or nominal atrioventricular delay (120 ms). Interventricular delay was defined as the time between the peaks of the right ventricular (RV) and left ventricular (LV) electrograms (RV-LV duration). CRT response was defined prospectively as a >15% reduction in LV end-systolic volume from implant to 6 months.

RESULTS

The cohort was 68% men, with a mean age of 65±11 years and LV ejection fraction of 28±8%. Longer RV-LV durations were significantly associated with CRT response ( P<0.01) for the entire cohort. Moreover, the benefit of AVO increased as RV-LV duration prolonged. At the longest quartile, there was a 4.26× greater odds of a remodeling response compared with nominal atrioventricular delays ( P=0.010).

CONCLUSIONS

Baseline interventricular delay predicted CRT response. At long RV-LV durations, AVO can increase the likelihood of reverse remodeling with CRT. AVO and LV lead location optimized to maximize interventricular delay may work synergistically to increase CRT response.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT00874445.

Acute biventricular hemodynamic effects of cardiac resynchronization therapy in right bundle branch block

BACKGROUND

Controversy remains regarding the use of cardiac resynchronization therapy (CRT) in patients with heart failure with right bundle branch block (RBBB) and reduced left ventricular (LV) ejection fraction. Moreover, little is known about acute hemodynamic changes with CRT in this subgroup as compared with patients with left bundle branch block (LBBB).

OBJECTIVE

The purpose of this study was to evaluate the acute biventricular hemodynamic response of CRT and other pacing configurations, including the effects of atrioventricular (AV) delay and atrial pacing, to understand the effects of CRT in RBBB.

METHODS

Forty patients (9 with RBBB and 31 with LBBB) undergoing CRT implantation underwent temporary pacing with varying configurations and AV delay. The acute hemodynamic response was assessed via invasive measurements of dP/dt_max (maximal rate of change in pressure) in the left ventricle (LV) as well as the right ventricle (RV) in patients with RBBB.

RESULTS

Patients with LBBB had a greater LV dP/dt_max response to CRT than did patients with RBBB. In patients with RBBB, single- or dual-site RV pacing configurations resulted in greater increases in RV dP/dt_max than did biventricular pacing. Optimal AV delays that maximized RV dP/dt_max were shorter than optimal AV delays for LV dP/dt_max. Furthermore, AV delays chosen to maximize improvement in RV dP/dt_max frequently resulted in negative effects on LV dP/dt_max.

CONCLUSION

These findings demonstrate a complex relationship between pacing configuration, AV delay, and hemodynamic responses. The biventricular hemodynamic response in patients with heart failure with RBBB might be improved by optimizing pacing modalities and AV delays. This may be particularly important in patients with diseases in whom RV failure predominates, such as patients with pulmonary hypertension and LV assist device.

Pulmonary Right Ventricular Resynchronization in Congenital Heart Disease

Background—

Electromechanical discoordination may contribute to long-term pulmonary right ventricular (RV) dysfunction in patients after surgery for congenital heart disease. We sought to evaluate changes in RV function after temporary RV cardiac resynchronization therapy.

Methods and Results—

Twenty-five patients aged median 12.0 years after repair of tetralogy of Fallot and similar lesions were studied echocardiographically (n=23) and by cardiac catheterization (n=5) after primary repair (n=4) or after surgical RV revalvulation for significant pulmonary regurgitation (n=21). Temporary RV cardiac resynchronization therapy was applied in the presence of complete right bundle branch block by atrial-synchronized RV free wall pacing in complete fusion with spontaneous ventricular depolarization using temporary electrodes. The q-RV interval at the RV free wall pacing site (mean 77.2% of baseline QRS duration) confirmed pacing from a late activated RV area. RV cardiac resynchronization therapy carried significant decrease in QRS duration ( P <0.001) along with elimination of the right bundle branch block QRS morphology, increase in RV filling time ( P =0.002), pulmonary artery velocity time integral ( P =0.006), and RV maximum +dP/dt ( P <0.001), and decrease in RV index of myocardial performance ( P =0.006). RV mechanical synchrony improved: septal-to-lateral RV mechanical delay decreased ( P <0.001) and signs of RV dyssynchrony pattern were significantly abolished. RV systolic stretch fraction reflecting the ratio of myocardial stretching and contraction during systole diminished ( P =0.001).

Conclusions—

In patients with congenital heart disease and right bundle branch block, RV cardiac resynchronization therapy carried multiple positive effects on RV mechanics, synchrony, and contraction efficiency.

Modalities of ventricular pacing for cardiac resynchronization therapy in patients with heart failure: a meta-analysis and systematic review

INTRODUCTION

This meta-analysis evaluated 14 studies which compared clinical and functional outcomes after different cardiac resynchronization therapy (CRT) modalities.

MATERIAL AND METHODS

Relevant studies were selected from the Medline, PubMed, Cochrane, and Google Scholar databases until June 27^th, 2016. We analyzed and compared the clinical outcomes (peak O₂ consumption and LVEF) and functional outcomes (6-min walk distance and quality of life (SF-36)) of HF patients who received different CRT modalities with outcomes in patients who received conventional univentricular therapy.

RESULTS

There was no significant difference in post-treatment 6-min walking distance between the biventricular (BiV) and left/right univentricular (LUV/RUV) groups (standardized difference in means = 0.049, 95% CI: -0.119 to 0.217, p = 0.566), or between the BiV and triventricular (TriV) groups (standardized difference in means = 0.035, 95% CI: -0.270 to 0.340, p = 0.822). Peak O₂ consumption was comparable between BiV and LUV/RUV groups (standardized difference in means = 0.306, 95% CI: -0.002 to 0.614, p = 0.052). Patients in the TriV group had a significant improvement in LVEF compared to the BiV group (standardized difference in means = 0.647, 95% CI: 0.313 to 0.982, p < 0.001).

CONCLUSIONS

TriV CRT is an attractive alternative to univentricular or BiV pacing for heart failure patients. It is necessary to conduct further large randomized trials to validate our present data.

Left univentricular pacing for cardiac resynchronization therapy

This review describes the rationale and published evidence for left univentricular pacing for cardiac resynchronization therapy, gives an overview of the existing optimization algorithms featuring this mode, and discusses future perspectives.

The Role of Atrioventricular and Interventricular Optimization for Cardiac Resynchronization Therapy

Many patients with left ventricular systolic dysfunction may benefit from cardiac resynchronization therapy; however, approximately 30% of patients do not experience significant clinical improvement with this treatment. AV and VV delay optimization techniques have included echocardiography, device-based algorithms, and several other novel noninvasive techniques. Using these techniques to optimize device settings has been shown to improve hemodynamic function acutely; however, the long-term clinical benefit is limited. In most cases, an empiric AV delay with simultaneous biventricular or left ventricular pacing is adequate. The value of optimization of these intervals in "nonresponders" still requires further investigation.

Optimal Cardiac Resynchronization Therapy Pacing Rate in Non-Ischemic Heart Failure Patients: A Randomized Crossover Pilot Trial

Background

The optimal pacing rate during cardiac resynchronization therapy (CRT) is unknown. Therefore, we investigated the impact of changing basal pacing frequencies on autonomic nerve function, cardiopulmonary exercise capacity and self-perceived quality of life (QoL).

Methods

Twelve CRT patients with non-ischemic heart failure (NYHA class II–III) were enrolled in a randomized, double-blind, crossover trial, in which the basal pacing rate was set at DDD-60 and DDD-80 for 3 months (DDD-R for 2 patients). At baseline, 3 months and 6 months, we assessed sympathetic nerve activity by microneurography (MSNA), peak oxygen consumption (pVO₂), N-terminal pro-brain natriuretic peptide (p-NT-proBNP), echocardiography and QoL.

Results

DDD-80 pacing for 3 months increased the mean heart rate from 77.3 to 86.1 (p = 0.001) and reduced sympathetic activity compared to DDD-60 (51±14 bursts/100 cardiac cycles vs. 64±14 bursts/100 cardiac cycles, p<0.05). The mean pVO₂ increased non-significantly from 15.6±6 mL/min/kg during DDD-60 to 16.7±6 mL/min/kg during DDD-80, and p-NT-proBNP remained unchanged. The QoL score indicated that DDD-60 was better tolerated.

Conclusion

In CRT patients with non-ischemic heart failure, 3 months of DDD-80 pacing decreased sympathetic outflow (burst incidence only) compared to DDD-60 pacing. However, Qol scores were better during the lower pacing rate. Further and larger scale investigations are indicated.

Trial Registration

ClinicalTrials.gov NCT02258061

Clinical, laboratory, and pacing predictors of CRT response

A decade of research has established the role of cardiac resynchronization therapy (CRT) in medically refractory, moderate to severe systolic heart failure (HF) with intraventricular conduction delay. CRT is an electrical therapy instituted to reestablish ventricular synchronization in order to improve cardiac function and favorably modulate the neurohormonal system. CRT confers a mortality benefit, improved HF hospitalizations, and functional outcome in this population, but not all patients consistently demonstrate a positive CRT response. The nonresponder rate varies from 20% to 40%, depending on the defined response criteria. Efforts to improve response to CRT have focused on a number of fronts. Methods to optimize the correction of electrical and mechanical dyssynchrony, which is the primary target of CRT, has been the focus of research, in addition to improving patient selection and optimizing post-implant care. However, a major issue in dealing with improving nonresponse rates has been finding an accurate and generally accepted definition of "response" itself. The availability of a standard consensus definition of CRT response would enable the estimation of nonresponder burden accurately and permit the development of strategies to improve CRT response. In this review, we define various aspects of "response" to CRT and outline variability in the definition criteria and the problems with its inconsistencies. We describe clinical, laboratory, and pacing predictors that influence CRT response and outcome and how to optimize response.