Comparative Analysis of Response to Cardiac Resynchronisation Therapy Upgrades in Patients with Implantable Cardioverter-Defibrillators and Pacemakers

Introduction: The efficacy of de novo cardiac resynchronisation therapy (CRT) in patients with heart failure (HF), left ventricular systolic dysfunction (LVSD), and a broad QRS morphology is well established. However, the optimal stage for upgrading patients with existing pacemakers (PPMs) or implantable cardioverter-defibrillators (ICDs) and HF with high-burden right ventricular (RV) pacing remains uncertain. Thus, this multicentre retrospective analysis compared patients with pre-existing PPMs or ICDs who underwent CRT upgrades to investigate the appropriate stage for CRT implantation in these patients and to assess the validity of treating both PPM and ICD recipients under the same recommendation level in the current guidelines. Materials and Methods: A total of 151 participants underwent analysis in this study, comprising 93 upgrades to cardiac resynchronisation therapy with pacemaker (CRT-P) and 58 upgrades to cardiac resynchronisation therapy with defibrillator (CRT-D) across three centres in the UK. The aim of the study was to investigate the safety and efficacy of upgrading to CRT from an existing conventional pacemaker or an ICD in the context of high-burden RV pacing. The analysis was conducted separately for each group, assessing changes in echocardiographic parameters, functional New York Heart Association (NYHA) class, and procedure-related complications. Results: The PPM group had a higher percentage RVP burden compared to the ICD group. Post-upgrade, NYHA functional class and EF and LV volumes improved in both groups; however, the response to an upgrade from a pacemaker was greater compared to an upgrade from an ICD. Post-procedural complication risks were similar across the two subgroups but significantly higher compared to de novo implantation. Conclusions: Within the CRT-P subgroup, participants exhibited better responses than their CRT-D counterparts, evident both in echocardiographic improvements and clinical outcomes. Furthermore, patients with non-ischemic cardiomyopathy (NICM) were better responders than those with ischaemic cardiomyopathy. These findings suggest that international guidelines should consider approaching each subgroup separately in the future.

Recruitment of the cardiac conduction system for optimal resynchronization therapy in failing heart

Heart failure (HF) is a leading health burden around the world. Although pharmacological development has dramatically advanced medication therapy in the field, hemodynamic disorders or mechanical desynchrony deteriorated by intra or interventricular conduction abnormalities remains a critical target beyond the scope of pharmacotherapy. In the past 2 decades, nonpharmacologic treatment for heart failure, such as cardiac resynchronization therapy (CRT) via biventricular pacing (BVP), has been playing an important role in improving the prognosis of heart failure. However, the response rate of BVP-CRT is variable, leaving one-third of patients not benefiting from the therapy as expected. Considering the non-physiological activation pattern of BVP-CRT, more efforts have been made to optimize resynchronization. The most extensively investigated approach is by stimulating the native conduction system, e.g., His-Purkinje conduction system pacing (CSP), including His bundle pacing (HBP) and left bundle branch area pacing (LBBAP). These emerging CRT approaches provide an alternative to traditional BVP-CRT, with multiple proof-of-concept studies indicating the safety and efficacy of its utilization in dyssynchronous heart failure. In this review, we summarize the mechanisms of dyssynchronous HF mediated by conduction disturbance, the rationale and acute effect of CSP for CRT, the recent advancement in clinical research, and possible future directions of CSP.

Chronology of cardiac dysfunction after permanent pacemaker implantation: an observational 2 year prospective study in North India

Background

The purpose of this study is to evaluate cardiac functions using transthoracic echocardiography, change in lead parameters and electrocardiogram (ECG) morphology in patients undergoing permanent pacemaker implantation over a follow-up period of 6 months.

Methods

This is a prospective study in patients undergoing permanent pacemaker implantation in a tertiary care hospital. Patients undergoing permanent pacemaker implantation were enrolled for up to one year and Echocardiographic parameters (by 2 blind operators) and ECG parameters were recorded at admission (within 24 h), before discharge (within 7 days of pacemaker implantation), after 1 month (± 7 days) and after 6 months (± 7 days) of follow-up.

Results

A total of 96 patients (60.4% males and 39.6% female, mean age 66.65 years) were implanted with permanent pacemaker. The mean QRS duration was 133.18 ms and increased significantly to 146.03 ms by 6 months despite septal lead placement in majority (92%) of patients. The mean baseline ejection fraction of 51.47 decreased significantly to 47.83 by 6 months. Diastolic parameters like left atrial volume index, early to late diastolic transmitral flow velocity (E/A) and early diastolic mitral annular tissue velocity (E/e′) showed a significant increase (> 5%) from baseline by the end of first week. By the end of first month, systolic dysfunction of RV sets in with significant (> 5%) change from baseline in parameters like Right ventricle myocardial performance index, transannular plane systolic excursion and right ventricle systolic excursion velocity (RVS′).

Conclusion

We have observed that pacemaker recipients with baseline reduced left ventricle (LV) systolic functions perform significantly worse compared to those with baseline normal cardiac functions and had a higher rate of deterioration of LV function. RV dysfunction is the first abnormality that occurs, by 1 week followed by LV dysfunction which starts by 1 month and the diastolic dysfunctions precede the systolic dysfunction. QRS duration also showed a gradual increase despite septal lead placement in majority (92%) and lead parameters showed no significant change over 6 months.

[Different phenotypes of mitral regurgitation in patients with right apical ventricular pacing: an echocardiographic approach in a heterogeneity of clinical scenarios]

The presence of mitral regurgitation (MR) in patients with right ventricular apical pacing can be the result of multiple phenomena. On the one hand, this stimulation causes an asynchronous activation of the left ventricle (LV) and the papillary muscles, leading to a deterioration of the LV ejection fraction and causing an inadequate closure of the valve apparatus. However, there is a wide heterogeneity of ischemic and non-ischemic myocardial conditions that can coexist with mechanical alteration of the LV and the mitral valve leading to or worsening MR in these patients, which can make the etiological determination of valvular regurgitation difficult. Transthoracic echocardiography study allows comprehensive evaluation of mitral valve regurgitation and ventricular function parameters and mechanical asynchrony as a result of artificial pacing. The comprehensive study of these phenomena is relevant in clinical decision-making to define those patients who benefit from cardiac resynchronization therapy to alleviate symptomatic MR.

Efficacy, Safety, and Performance of Isolated Left vs. Right Ventricular Pacing in Patients with Bradyarrhythmias: A Randomized Controlled Trial

Background

Considering the potential deleterious effects of right ventricular (RV) pacing, the hypothesis of this study is that isolated left ventricular (LV) pacing through the coronary sinus is safe and may provide better clinical and echocardiographic benefits to patients with bradyarrhythmias and normal ventricular function requiring heart rate correction alone.

Objective

To assess the safety, efficacy, and effects of LV pacing using an active-fixation coronary sinus lead in comparison with RV pacing, in patients eligible for conventional pacemaker (PM) implantation.

Methods

Randomized, controlled, and single-blinded clinical trial in adult patients submitted to PM implantation due to bradyarrhythmias and systolic ventricular function ≥ 0.40. Randomization (RV vs. LV) occurred before PM implantation. The main results of the study were procedural success, safety, and efficacy. Secondary results were clinical and echocardiographic changes. Chi-squared test, Fisher's exact test and Student's t-test were used, considering a significance level of 5%.

Results

From June 2012 to January 2014, 91 patients were included, 36 in the RV Group and 55 in the LV Group. Baseline characteristics of patients in both groups were similar. PM implantation was performed successfully and without any complications in all patients in the RV group. Of the 55 patients initially allocated into the LV group, active-fixation coronary sinus lead implantation was not possible in 20 (36.4%) patients. The most frequent complication was phrenic nerve stimulation, detected in 9 (25.7%) patients in the LV group. During the follow-up period, there were no hospitalizations due to heart failure. Reductions of more than 10% in left ventricular ejection fraction were observed in 23.5% of patients in the RV group and 20.6% of those in the LV group (p = 0.767). Tissue Doppler analysis showed that 91.2% of subjects in the RV group and 68.8% of those in the LV group had interventricular dyssynchrony (p = 0.022).

Conclusion

The procedural success rate of LV implant was low, and the safety of the procedure was influenced mainly by the high rate of phrenic nerve stimulation in the postoperative period.

Chronic Right Ventricular Pacing in the Heart Failure Population

Purpose of Review

We review the trials that have demonstrated potentially harmful effects from right ventricular (RV) apical pacing as well as reviewing the evidence of alternative RV pacing sites and cardiac resynchronization therapy (CRT) for patients who have heart failure and atrioventricular (AV) block.

Recent Findings

The role of CRT in patients with AV block and impaired left ventricular function remains an important consideration. The BLOCK HF trial demonstrated better outcomes with CRT pacing over RV pacing in patients with left ventricular systolic dysfunction (LVSD) and AV block who were expected to have a high RV pacing burden, but failed to demonstrate a mortality benefit.

Summary

CRT seems to have a beneficial effect on left ventricular reverse remodeling, systolic function, and clinical outcomes in patients with New York Heart Association (NYHA) functional class I–III heart failure, moderate to severe LVSD, and AV block compared to RV pacing. However, it is less clear whether there is a similar benefit from CRT in patients with a high percentage of RV pacing who have normal or mild LVSD in the treatment of AV block.

Early Right Ventricular Apical Pacing-Induced Gene Expression Alterations Are Associated with Deterioration of Left Ventricular Systolic Function

The chronic high-dose right ventricular apical (RVA) pacing may have deleterious effects on left ventricular (LV) systolic function. We hypothesized that the expression changes of genes regulating cardiomyocyte energy metabolism and contractility were associated with deterioration of LV function in patients who underwent chronic RVA pacing. Sixty patients with complete atrioventricular block and preserved ejection fraction (EF) who underwent pacemaker implantation were randomly assigned to either RVA pacing (n = 30) group or right ventricular outflow tract (RVOT) pacing (n = 30) group. The mRNA levels of OPA1 and SERCA2a were significantly lower in the RVA pacing group at 1 month's follow-up (both p < 0.001). Early changes in the expression of selected genes OPA1 and SERCA2a were associated with deterioration in global longitudinal strain (GLS) that became apparent months later (p = 0.002 and p = 0.026, resp.) The altered expressions of genes that regulate cardiomyocyte energy metabolism and contractility measured in the peripheral blood at one month following pacemaker implantation were associated with subsequent deterioration in LV dyssynchrony and function in patients with preserved LVEF, who underwent RVA pacing.

Deterioration of left ventricular systolic function in extended Pacing to Avoid Cardiac Enlargement (PACE) trial: the predictive value of early systolic dyssynchrony

AIMS

Biventricular (BiV) pacing was superior to right ventricular apical (RVA) pacing at extended follow-up in the Pacing to Avoid Cardiac Enlargement (PACE) trial. Early pacing-induced systolic dyssynchrony (DYS) might be related to mid-term result. However, it remains unknown whether early pacing-induced DYS can predict long-term reduction of left ventricular (LV) systolic function.

METHODS AND RESULTS

Patients with standard pacing indications and normal LV ejection fraction (LVEF) were randomized either to BiV (n = 89) or RVA (n = 88) pacing. Seventy-four patients in the RVA group and 72 in the BiV pacing group completed follow-up longer than 2 years. Serial echocardiography was performed with DYS assessed by tissue Doppler imaging, and the early pacing-induced DYS was defined as >33 ms by using standard deviation of the time to peak systolic velocity (Dyssynchrony Index) in a 12-segment model of LV at 1 month. There were 46 (32%) patients having early pacing-induced DYS that was more prevalent in the RVA pacing group than that in the BiV pacing group (50.7 vs. 12.3%, χ(2) = 25.1, P < 0.001) despite the similar DYS between the two groups at baseline (30 ± 13 vs. 26 ± 11 ms, P = 0.051). At a median follow-up of 4.8 years, patients developing early DYS had lower LVEF (53.2 ± 9.4 vs. 60.9 ± 8.0%, P < 0.001) and larger LV end-systolic volume (40.3 ± 23.7 vs. 29.3 ± 13.4 mL, P < 0.001) than those without DYS. Significant EF reduction (defined as ≥5%) occurred in 71.7% (33 in 46) of patients with DYS, but only in 30% (30 in 100) in those without DYS (χ(2) = 22.4, P < 0.001). Further analysis showed that both DYS at 1 month [odds ratio (OR): 3.113, P = 0.013] and RVA pacing (OR: 7.873, P < 0.001) independently predicted the deterioration of LV systolic function with pacing period of 4.8 years.

CONCLUSION

Early pacing-induced DYS is a significant predictor of reduction of LV systolic function for long-term pacing, which could be prevented by BiV pacing at relatively long-period follow-up.

CLINICAL TRIAL REGISTRATION

Centre for Clinical Trials number, CUHK_CCT00037 (URL: http://www.cct.cuhk.edu.hk/Registry/publictrialrecord.aspx?trialid=CUHK_CCT00037).

Cardiac resynchronization therapy is appropriate for all patients requiring chronic right ventricular pacing: the pro perspective

Long-term right ventricular pacing has deleterious effects on the left ventricle (LV). The risk of pacemaker-induced cardiomyopathy (PICM) seems to be lower in patients with a normal LV ejection fraction (LVEF). Patients developing PICM respond favorably to a cardiac resynchronization therapy upgrade, suggesting that the dysfunction is partially reversible. Biventricular pacing has emerged as a treatment and/or prevention of PICM. Cumulative pacing greater than 40% of the time is considered the most important risk factor for PICM. No organizational guidelines exist for preventive biventricular pacing. The decision to pursue biventricular pacing should be individualized.

Cardiac Resynchronisation Therapy and Heart Failure: Persepctive from 5P Medicine

Chronic heart failure is still a major challenge for healthcare. Currently, cardiac resynchronisation therapy (CRT) has been incorporated into the updated guideline for patients with heart failure, left ventricular ejection fraction ≤35 % and prolonged QRS duration. With 20 years of development, the concept of 'from bench to bedside' has been illustrated in the field of CRT. Given the fact that the indications of CRT keep evolving, the role of CRT is not limited to the curative method for heart failure. We therefore summarise with the perspective of 5P medicine - preventive, personalised, predictive, participatory, promotive, to review the benefit of CRT in the prevention of heart failure in those with conventional pacemaker indications, the individualised assessment of patient's selection, the predictor of responders of CRT, and the obstacles hindering the more application of CRT and the future development of this device therapy.

Effect of induced LV dyssynchrony by right ventricular apical pacing on all-cause mortality and heart failure hospitalization rates at long-term follow-up

BACKGROUND

Right ventricular apical (RVA) pacing may induce left ventricular (LV) dyssynchrony. The long-term prognostic implications of induction of LV dyssynchrony were retrospectively evaluated in a cohort of patients who underwent RVA pacing.

METHODS

A total of 169 patients (62 ± 13 years, 69% male) with high RVA pacing burden were included. Echocardiographic evaluation of LV volumes, ejection fraction, and dyssynchrony were performed before and after device implantation. LV dyssynchrony was assessed by 2-dimensional radial strain speckle tracking echocardiography. Based on the median LV dyssynchrony value after RVA pacing, the patient population was dichotomized (induced and noninduced LV dyssynchrony groups) and was followed up for the occurrence of all-cause mortality and heart failure (HF) hospitalization.

RESULTS

Baseline mean LV ejection fraction was 51 ± 11%. Median LV dyssynchrony value was 40 ms (12-85 ms) before RVA pacing and increased to 91 ms (81-138 ms) after a median of 13 months (3-26 months) after RVA pacing. Median follow-up duration was 70 months (interquartile range 42-96 months). Patients with induced LV dyssynchrony, defined as LV dyssynchrony value superior to the median at follow-up (≥91 ms), showed higher mortality rates (5% and 27% vs. 1% and 3% at 3 and 5 years follow-up; log-rank P = 0.003) and HF hospitalization rates (18% and 24% vs. 3% and 4% at 3 and 5 years follow-up; log-rank P < 0.001) than patients with LV dyssynchrony <91 ms after RVA pacing. A multivariate model was developed to identify independent associates of a combined endpoint of all-cause mortality or HF hospitalization. Induction of LV dyssynchrony was independently associated with increased risk of combined endpoint (HR [95% CI]: 3.369 [1.732-6.553], P < 0.001).

CONCLUSION

Induction of LV dyssynchrony by RVA pacing is associated with worse long-term mortality and increased HF hospitalization rates.

The zebrafish as a novel animal model to study the molecular mechanisms of mechano-electrical feedback in the heart

Altered mechanical loading of the heart leads to hypertrophy, decompensated heart failure and fatal arrhythmias. However, the molecular mechanisms that link mechanical and electrical dysfunction remain poorly understood. Growing evidence suggest that ventricular electrical remodeling (VER) is a process that can be induced by altered mechanical stress, creating persistent electrophysiological changes that predispose the heart to life-threatening arrhythmias. While VER is clearly a physiological property of the human heart, as evidenced by "T wave memory", it is also thought to occur in a variety of pathological states associated with altered ventricular activation such as bundle branch block, myocardial infarction, and cardiac pacing. Animal models that are currently being used for investigating stretch-induced VER have significant limitations. The zebrafish has recently emerged as an attractive animal model for studying cardiovascular disease and could overcome some of these limitations. Owing to its extensively sequenced genome, high conservation of gene function, and the comprehensive genetic resources that are available in this model, the zebrafish may provide new insights into the molecular mechanisms that drive detrimental electrical remodeling in response to stretch. Here, we have established a zebrafish model to study mechano-electrical feedback in the heart, which combines efficient genetic manipulation with high-precision stretch and high-resolution electrophysiology. In this model, only 90 min of ventricular stretch caused VER and recapitulated key features of VER found previously in the mammalian heart. Our data suggest that the zebrafish model is a powerful platform for investigating the molecular mechanisms underlying mechano-electrical feedback and VER in the heart.