Survival After Rate-Responsive Programming in Patients With Cardiac Resynchronization Therapy-Defibrillator Implants Is Associated With a Novel Parameter: The Heart Rate Score

High Initial Heart Rate Score is an Independent Predictor of New Atrial High-Rate Episodes in Pacemaker Patients with Sinus Node Dysfunction

BACKGROUND

Heart Rate Score (HRSc), the percent of atrial depolarizations in the largest paced/sensed 10-bpm histogram bin recorded in cardiac devices, is associated with several adverse outcomes but it remains uncertain if HRSc independently predicts atrial high-rate episodes (AHREs) in patients with sinus node dysfunction (SND) undergoing pacemaker (PM) implantation.

OBJECTIVE

To determine if initial HRSc post-PM implant predicts new-onset AHREs in patients with SND.

METHODS

Patients had Boston Scientific PMs implanted for SND from 2012-2021 at Cleveland Clinic, University of Occupational and Environmental Health, Japan, Kyushu Rosai Hospital, and JCHO Kyushu Hospital. Patients were excluded if they had atrial fibrillation before PM implant or AHREs within 3-months post-implant. Subsequent AHREs post-implant were evaluated and correlated with HRSc.

RESULTS

Over 48.9 (IQR 25.7-50.4) months, 130 consecutive PM patients (76±10 years, 40% male) had a median initial HRSc of 74(57-86)%. AHREs defined by >1%, >6h/day burden, and ATR events>24h developed in 27/130(21%), 15/130(12%), and 9/130(7%), respectively. For each definition, patients with HRSc≥80% had higher occurrence of AHREs than those with HRSc<80% (both p=0.008, log-rank test). After adjusting for age, race, comorbidities, left ventricular ejection fraction, left atrial diameter, and cumulative %RA/RV pacing, initial HRSc ≥80% (HR:3.33, 95% CI:1.35-8.18; P=0.009) and male sex (HR:2.59, 95% CI:1.06-6.33; P=0.04) independently predicted AHREs.

CONCLUSION

HRSc≥80% is associated with new-onset, device-determined AHREs for patients undergoing PM implant for SND. HRSc may have prognostic and therapeutic implications.

Minute ventilation sensor-driven rate response as a part of cardiac resynchronization therapy optimization in older patients

BACKGROUND

Chronotropic incompetence (CI) is common among elderly cardiac resynchronization therapy pacemaker (CRT-P) patients on optimal medical therapy. This study aimed to evaluate the impact of optimized rate-adaptive pacing utilizing the minute ventilation (MV) sensor on exercise tolerance.

METHODS

In a prospective, multicenter study, older patients (median age 76 years) with a guideline-based indication for CRT were evaluated following CRT-P implantation. If there was no documented CI, requiring clinically rate-responsive pacing, the device was programmed DDD at pre-discharge. At 1 month, a 6-min walk test (6MWT) was conducted. If the maximum heart rate was < 100 bpm or < 80% of the age-predicted maximum, the response was considered CI. Patients with CI were programmed with DDDR. At 3 months post-implant, the 6MWT was repeated in the correct respective programming mode. In addition, heart rate score (HRSc, defined as the percentage of all sensed and paced atrial events in the single tallest 10 bpm histogram bin) was assessed at 1 and 3 months.

RESULTS

CI was identified in 46/61 (75%) of patients without prior indication at enrollment. MV sensor-based DDDR mode increased heart rate in CI patients similarly to non-CI patients with intrinsically driven heart rates during 6MWT. Walking distance increased substantially with DDDR (349 ± 132 m vs. 376 ± 128 m at 1 and 3 months, respectively, p < 0.05). Furthermore, DDDR reduced HRSc by 14% (absolute reduction, p < 0.001) in those with more severe CI, i.e., HRSc ≥ 70%.

CONCLUSION

Exercise tolerance in older CRT-P patients can be further improved by the utilization of an MV sensor.

Activated rate-response is associated with increased mortality risk in cardiac device carriers with acute heart failure

AIMS

This study investigated whether an activated R-mode in patients carrying a cardiac implantable electronic device (CIED) is associated with worse prognosis during and after an episode of acutely decompensated heart failure (AHF).

METHODS

Six hundred and twenty-three patients participating in an ongoing prospective cohort study that phenotypes and follows patients admitted for AHF were studied. We compared CIED carriers with activated R-mode stimulation (CIED-R) to CIED carriers not in R-mode (CIED-0) and patients without CIEDs (no-CIED). The independent impact of R-mode activation on 12-month all-cause death was examined using uni- and multivariable Cox proportional hazards regression taking into account potential confounders, and hazard ratios (HR) with their 95% confidence intervals (CI) were reported.

RESULTS

Mean heart rate on admission was lower in CIED-R (n = 37, 16% women) vs. CIED-0 (n = 64, 23% women) or no-CIED (n = 511, 43% women): 70 bpm vs. 80 bpm or 82 bpm; both p<0.001. In-hospital mortality was similar across groups, but age- and sex-adjusted all-cause 12-month mortality risk was differentially affected by R-mode activation; CIED-R vs. CIED-0: HR 2.44, 95%CI 1.25-4.74; CIED-R vs. no-CIED: HR 2.61, 95%CI 1.59-4.29. These effects persisted after multivariable adjustment for potential confounders. Within CIED-R, mortality risk was similar in patients with pacemakers vs. ICDs and in subgroups with left ventricular ejection fraction (LVEF) <50% vs. ≥50%.

CONCLUSION

In patients admitted with AHF, R-mode stimulation was associated with a significantly increased 12-month mortality risk. Our findings shed new light on "admission heart rate" as a potentially treatable target in AHF. Our data are compatible with the concept that chronotropic incompetence contributes to an adverse outcome in these patients and may not be adequately treated through accelerometer-based R-mode stimulation.

The impact of chronotropic incompetence on atrioventricular conduction times in heart failure patients

BACKGROUND

Intrinsic atrioventricular (AV) conduction is used to optimize AV intervals with cardiac resynchronization therapy (CRT) in most device algorithms. Atrial pacing and heart rate affect conduction times, but little is known regarding differeces among chronotropic incompetent(CI) and competent(CC) patients to guide programming.

METHODS

RAVE was a multicenter prospective trial of CRT patients. Heart rate was increased with incremental atrial pacing and with submaximal exercise. According to the maximal heart rate achieved during exercise, patients were classified as either CI or CC. For CI patients, an additional symptom-limited exercise with rate-adaptive pacing activated was performed. Intracardiac intervals were measured from the implantable lead electrograms in multiple postures.

RESULTS

There were 12 subjects with CI and 24 with CC. With atrial pacing, AV interval immediately increased and gradually increased with incremental atrial pacing in all patients. However, the changes in the atrial to right ventricular (ARV) and atrial to left ventricular (ALV) intervals with increasing atrial pacing rates were about threefold greater in CI patients compared to CC patients (24.3 ± 28.9 vs. 7.2 ± 5.5 ms/10 bpm for ARV and 22.7 ± 25.6 vs. 7.1 ± 5.7 ms/10 bpm for ALV in the standing position, p < 0.05). In CI pacing with rate-adaptive pacing during exercise, AV interval changes with paced heart rate were variable.

CONCLUSIONS

The AV response to overdrive atrial pacing at rest may provide a simple means of identifying chronotropic competence in CRT patients. For patients with CI, who often require rate-adaptive atrial pacing, rate-adaptive AV algorithms should be adjusted individually.

Importance of resting heart rate

Resting heart rate is a determinant of cardiac output and physiological homeostasis. Although a simple, but critical, parameter, this vital sign predicts adverse outcomes, including mortality, and development of diseases in otherwise normal and healthy individuals. Temporal changes in heart rate can have valuable predictive capabilities. Heart rate can reflect disease severity in patients with various medical conditions. While heart rate represents a compilation of physiological inputs, including sympathetic and parasympathetic tone, aside from the underlying intrinsic sinus rate, how resting heart rate affects outcomes is uncertain. Mechanisms relating resting heart rate to outcomes may be disease-dependent but why resting heart rate in otherwise healthy, normal individuals affects outcomes remains obscure. For specific conditions, physiologically appropriate heart rate reductions may improve outcomes. However, to date, in the normal population, evidence that interventions aimed at reducing heart rate improves outcomes remains undefined. Emerging data suggest that reduction in heart rate via vagal activation and/or sympathetic inhibition is propitious.

Initial heart rate score predicts new-onset atrial tachyarrhythmias in pacemaker patients

AIMS

Heart rate score (HRSc), the per cent of atrial paced and sensed event in the largest 10 b.p.m. rate histogram bin of a pacemaker, predicts survival in patients with cardiac devices. No correlation between HRSc and development of atrial fibrillation (AF) has been reported. In this study, we evaluated the relationship between pacemaker post-implantation HRSc and the incidence of newly developed atrial tachyarrhythmias (ATAs).

METHODS AND RESULTS

Patients with dual-chamber pacemakers, implanted 2013-17, with the LATITUDE remote monitoring data with ≥600 000 beats of histogram data collected at baseline were included (N = 34 543). Heart rate score was determined from the initial 3-month post-implantation histogram data. Patients were excluded if they had ATAs, defined as atrial high-rate episodes >5 min or >1% of right atrial beats >170 b.p.m. during the initial 3 months post-implantation. New ATAs, after the baseline period, were defined by each of the following: >1, >10, or >25% of atrial beats >170 b.p.m. or atrial tachycardia response (ATR) events >24 h. Patients were followed a median of 2.8 (1.0-4.0) years. The incidence of ATAs increased in proportion to HRSc (log-rank P-value <0.001), and the initial HRSc ≥70% was associated with increased ATAs by all definitions. Patients with initial HRSc ≥70% were older, had a higher percentage of right atrium pacing (%RA pacing), had a lower percentage of right ventricular pacing (%RV pacing), and were more likely programmed with rate-response vs. subjects with HRSc <70%. Initial HRSc (hazard ratio: 1.07, 95% confidence interval: 1.05-1.09; P < 0.0001) independently predicted ATAs after adjusting for age, gender, %RV pacing, and rate-response programming. The %RA pacing and initial HRSc were correlated.

CONCLUSION

Heart rate score independently predicts any subsequent duration of ATAs in pacemaker patients.

Atrial fibrillation associated with heart failure treated by a 2-lead CRT-DX system (BIO-AffectDX): Study design and clinical protocol

Background

Evidence to support use of cardiac resynchronization therapy (CRT) among patients with both heart failure (HF) and atrial fibrillation (AF) is largely limited to retrospective or post hoc subanalyses. Data from a prospectively enrolled and contemporary cohort are needed.

Objective

We aim to better characterize the changes from baseline in HF patients with concomitant AF subsequently implanted with a 2-lead CRT-DX system capable of sensing in the atrium, aggregating diagnostics, and delivering CRT therapy. The primary objective of this study is to evaluate the percentage of all HF subjects with an improvement in a clinical composite score from pre-CRT implant to 12 months.

Methods

The study is a US-based, prospective, observational multicenter clinical trial conducted at up to 50 sites and enrolling approximately 400 subjects with a follow-up period of 1 year. Multiple subject assessments, atrial rhythm status, and device interrogation will be collected at follow-up visits occurring at 3, 6, and 12 months postimplant.

Results

A Clinical Events Committee will adjudicate subject HF events, arrhythmia events, death events, and all device-classified ventricular tachycardia and ventricular fibrillation episodes with treatment that are collected throughout the follow-up period. Their decisions are based on independent physician review of the data from sites and device interrogation.

Conclusion

The BIO-AffectDX study aims to provide further insight into the expected outcomes from CRT treatment in patients with HF and AF.

Heart rate score and outcomes in ICD patients: insights from the prospective randomized INTRINSIC RV trial

BACKGROUND

Heart rate score (HRSc), the percentage of atrial sensed and paced beats in the largest 10 beat/min bin of a device histogram and mean intrinsic heart rate (MIHR), predicted survival in nonrandomized studies of implantable defibrillator (ICD) patients. We evaluated whether HRSc and MIHR independently predicted mortality and heart failure (HF) hospitalization in the prospective, randomized, controlled INTRINSIC RV trial.

METHODS AND RESULTS

The INTRINSIC RV trial enrolled 1530 patients receiving dual-chamber ICDs. This analysis involves patients (n = 1471) for whom MIHR and HRSc data were available. Mean follow-up was 10.4 months. The relationship between pre-randomization MIHR and HRSc on the primary endpoint of all-cause mortality and HF hospitalization was assessed using multivariate regression and Cox modeling. As categorical variables, MIHR > 70 bpm and HRSc > 70% were considered high.

RESULTS

The median baseline MIHR and HRSc were 74 (IQR = 16) and 50% (IQR = 20) respectively. As a continuous variable, for every 1% increase in HRSc, death/HF hospitalization increased by 1% (95%CI: 1.002-1.017; p = 0.01). Regression analysis showed baseline MIHR was associated with HRSc (p = 0.01); for every 1 beat/min increase in MIHR, HRSc increased by 1.8%. A MIHR > 70 bpm and HRSc ≥ 70% predicted, but were independently associated with, the primary endpoint (HR: 1.39; 95%CI: 1.10-1.76, p = 0.005 for MIHR and HR: 1.654; 95%CI: 1.11-2.46, p = 0.01 for HRSc). Male gender (HR: 0.75), history of HF (HR: 1.29), and atrial fibrillation (HR: 1.37) also predicted death/hospitalization in the Cox model.

CONCLUSIONS

In this large, prospectively studied ICD population, HRSc was a robust and independent predictor of death/HF hospitalization. High MIHR and high HRSc were associated but each predicted outcomes independently.

Lower rate limit for pacing by cardiac resynchronization defibrillators: Should lower rate programming be reconsidered?

BACKGROUND

No real-world large database associates lower rate limit (LRL) programming and survival of subjects with cardiac resynchronization therapy-defibrillators (CRT-Ds).

OBJECTIVE

The purpose of this study was to test the hypothesis that lower LRL programming is independently associated with survival, and that LRL and heart rate score (HrSc) are associated.

METHODS

All dual-chamber CRT-D devices in the Remote Patient Monitoring (RPM) ALTITUDE database (2006-2011) were queried. Baseline HrSc was defined as the percentage of all atrial sensed and paced beats in the tallest 10-beat histogram bin postimplant. LRL was assessed during repeated RPM uploads. Using a Cox model multivariable analysis, relationships between LRL, survival, HrSc, and other variables were evaluated. Survival was determined by query of death indices.

RESULTS

Data analyzed included 61,881 subjects (mean follow-up 2.9 years). LRL ranged from 40 to 85 bpm. Baseline lower LRL was associated with younger age, less atrial fibrillation, female sex, and lower HrSc (P <.001 for all covariates). Lower LRL was associated with improved survival, with LRL 40 associated with the largest survival benefit. This was significant for all 3 HrSc subgroups (P <.001). An interaction between HrSc and LRL was observed, with the largest survival difference between HrSc groups observed at LRL-40 (P <.001).

CONCLUSION

LRL programming and HrSc were associated, and lower values of both were associated with improved survival in a large database of CRT-D subjects. Relationships between survival, LRL programming, and HrSc merit further study.

Survival after left ventricular assist device implantation correlates with a novel device-based measure of heart rate variability: the heart rate score

OBJECTIVES

The heart rate score (HRS) serves as a device-based measure of impaired heart rate variability and is an independent predictor of death in patients with heart failure and a cardiac implantable electrical device. However, no data are available for predicting death from the HRS in patients with end stage heart failure and a left ventricular assist device.

METHODS

From November 2011 to July 2018, a total of 56 patients with a pre-existing cardiac implantable electrical device underwent left ventricular assist device implantation at our 2 study sites. The ventricular HRS was calculated retrospectively during the first cardiac implantable electrical device follow-up examination following the index hospitalization. Survival during follow-up was correlated with initial HRS.

RESULTS

During the follow-up period, 46.4% of the patients (n = 26) died. The median follow-up period was 33.2 months. The median HRS after the index hospitalization was 41.1 ± 21.8%. More patients with an HRS >65% died compared to patients with an HRS <30% (76.9% vs 14.4%; P = 0.007).

CONCLUSIONS

In our multicentre experience, survival of patients after an left ventricular assist device implant correlates with the HRS. After confirmation of our findings in a larger cohort, the effect of rate-responsive pacing will be within the scope of further investigation.

Heart rate score, a measure related to chronotropic incompetence in pacemaker patients

BACKGROUND

Heart rate score (HrSc) ≥70% in cardiac resynchronization therapy defibrillator and implantable cardioverter-defibrillator subjects predicts 5-year mortality risk. A high HrSc suggests few sensed cardiac cycles above the programmed lower rate.

OBJECTIVE

To determine if HrSc is related to chronotropic incompetence (CI) in pacemaker (PM) subjects.

METHODS

HrSc is the percentage of all atrial-paced and sensed events in the single tallest 10 beats/min histogram bin programmed to DDD 60/min. The prospective LIFE study of PM subjects examined multiple treadmill-based measures of CI. The 1-month postimplant DDD 60/min PM rate histogram prior to treadmill was retrospectively analyzed for HrSc. Measures of CI were applied to submaximal treadmill data in the DDD mode. HrSc was compared to these CI measures and to clinical indications for PM.

RESULTS

The 1-month histogram demonstrated HrSc ≥70% in 43% of subjects. HrSc ≥70% correlated with a clinical diagnosis of sick sinus syndrome (P < .001). CI was present in 34%-88% of subjects by treadmill-based measures. Agreement between treadmill-based measures for CI was poor and varied from 39% to 83%. HrSc ≥70%, as a measure of CI, was most highly correlated with unpaced heart rate <70% of age-predicted maximum heart rate (67%) (odds ratio 3.7, P < .001).

CONCLUSIONS

HrSc ≥70% correlates with treadmill measures of CI and clinical sick sinus syndrome. HrSc ≥70% is a measure of CI in PM subjects that is inexpensive, repeatable, and quantitative.

Impact of a poor functional capacity on the clinical outcomes in patients with a pacemaker implantation -Results from the Japanese Heart Rhythm Society Registry

BACKGROUND

Functional capacity (FC) correlates with mortality in various cardiovascular diseases. The aim of this study was to examine whether cardiac pacemaker implantations improve the FC and affect the prognosis.

METHODS AND RESULTS

We prospectively enrolled 621 de novo pacemaker recipients (age 76 ± 9 years, 50.7% male). The FC was assessed by metabolic equivalents (METs) during the implantation and periodically thereafter. The patients were a priori classified into poor FC (<2 METs, n = 40), moderate FC (2 ≤ METs < 4, n = 239), and good FC (≥4 METs, n = 342). Three months after the pacemaker implantation, poor FC or moderate FC patients improved to a good FC by 43%. The distribution of the three FCs remained at those levels until after 1 year of follow-up (P = .18). During a median follow-up of 2.4 years, 71 patients (11%) had cardiovascular hospitalizations and 35 (5.6%) all-cause death. A multivariate Cox analysis revealed that a poor FC at baseline was an independent predictor of both cardiovascular hospitalization (hazard ratio [HR] 2.494, P = .012) and all-cause death (HR 3.338, P = .016). One year after the pacemaker implantation, the eight who remained with a poor FC had a high mortality rate of 37.5% (P < .01).

CONCLUSION

Approximately half of the poor or moderate FC patients improved to good FC 3 months after the pacemaker implantation. The baseline FC predicted the prognosis, and patients with an improved FC after the pacemaker implantation had a better prognosis.

Rationale and feasibility of the atrioventricular single-lead ICD systems with a floating atrial dipole (DX) in clinical practice

Cardiac implantable electronic devices establish proper therapy for the prevention of sudden cardiac death, significantly reducing the morbidity and mortality of patients with arrhythmias and heart failure. It is well-known that the number of electrodes increases the risk of complications. To preserve the benefit of atrial sensing without the need to implant an additional lead, a single-lead ICD system with a floating atrial dipole (DX ICD lead) has been developed. Besides all of the potential benefits, the necessity of a reliable and stable atrial sensing via the floating dipole could be the main concern against the use of this lead type. In the current generation of DX devices, the specially filtered atrial signal seems to be high enough and stable over time, which is crucial in the early detection of atrial arrhythmias, discrimination between different forms of tachycardias in order to prevent inappropriate ICD therapy, and achieving an optimal atrioventricular and interventricular synchrony in patients with a two-lead CRT-DX system. The present review summarizes the benefits and potential drawbacks of the DX ICD systems based on the available literature, furthermore, proposes an evidence-based algorithm of ICD type selection.

CardioMEMSTM System in the Daily Management of Heart Failure: Review of Current Data and Technique of Implantation

INTRODUCTION

Heart failure (HF) leads to significant morbidity and mortality and imposes a large economic burden. Although there have been several advances in HF monitoring and management, HF-rehospitalization remains a significant problem. Remote monitoring of HF to detect early signs of decompensation has emerged in past years as an option to prevent or reduce the incidence of HF rehospitalization. The CardioMEMS^TM HF system is a wireless pulmonary artery (PA) pressure monitoring system that detects changes in PA pressure and transmits data to the healthcare provider. Since changes in PA pressure happen early in the course of HF decompensation, the CardioMEMS^TM system allows the provider to institute timely intensification of HF therapies to alter the course. In trial and registry data, the use of the CardioMEMS^TM HF system has been associated with reduction in HF hospitalization, improvement in quality of life, symptoms, and physical activity.

AREAS COVERED

This review will focus on the available data supporting its utilization in patients with HF.

EXPERT OPINION

CardioMEMS^TM is relatively safe and cost-effective, reduces heart failure hospitalization rates, and fits into intermediate to high-value medical care.

Heart rate score predicts mortality independent of shocks in ICD and CRT-D patients

BACKGROUND

Heart Rate Score (HrSc), a novel index found to predict mortality in patients with implantable defibrillator (ICD) and cardiac resynchronization defibrillator (CRT-D) devices, is associated with mortality in ICD and CRT-D recipients when HrSc is ≥ 70%. Implantable defibrillator shocks have also been associated with increased mortality in ICD and CRT-D recipients. The objective of this study was to evaluate the relationships between HrSc, shocks, and mortality in ICD and CRT-D patients.

METHODS

HrSc was calculated from atrial sensed and paced rate histograms collected from the 2006-2011 ALTITUDE remote interrogation database. Shocks were determined in the first year of follow-up. Mortality was assessed over the next 4 years by the Social Security Death Index. Four multivariable models were run: ICD and CRT-D, shock and no shock, with mortality as the outcome and HrS as predictor.

RESULTS

Data from 49,358 ICD and 55,953 CRT-D patients were divided into HrSc: ≥ 70%, 30-69%, and < 30%. Shock rates differed between HrSc groups (p < 0.001) for ICD and CRT-D patients. However, the lowest mortality risk HrSc (< 30%) had the highest shock rate. Both highest HrSc (> 70%; p < 0.001) and shocks (p < 0.001) predicted mortality during follow-up. Mortality was unrelated to interactions between HrSc and shocks in ICD patients (p = 0.275) or CRT-D patients (p < 0.079). Comparing HrSc ≥ 70% to HrSc < 30%, HrSc ≥ 70% predicted mortality in CRT-D (HR 1.40; 95% CI 1.29-1.52) and ICD (HR 1.23; 95% CI 1.11-1.36) patients regardless of shocks (P < 0.001 for both).

CONCLUSIONS

Patients with ICDs or CRT-Ds having the lowest mortality risk HrSc had the highest shock rate. Shocks and HrSc appear to complement each other as predictors of mortality.

Chronotropic Incompetence in Chronic Heart Failure

Chronotropic incompetence (CI) is generally defined as the inability to increase the heart rate (HR) adequately during exercise to match cardiac output to metabolic demands. In patients with heart failure (HF), however, this definition is unsuitable because metabolic demands are unmatched to cardiac output in both conditions. Moreover, HR dynamics in patients with HF differ from those in healthy subjects and may be affected by β-blocking medication. Nevertheless, it has been demonstrated that CI in HF is associated with reduced functional capacity and poor survival. During exercise, the normal heart increases both stroke volume and HR, whereas in the failing heart, contractility reserve is lost, thus rendering increases in cardiac output primarily dependent on cardioacceleration. Consequently, insufficient cardioacceleration because of CI may be considered a major limiting factor in the exercise capacity of patients with HF. Despite the profound effects of CI in this specific population, the issue has drawn limited attention during the past years and is often overlooked in clinical practice. This might partly be caused by a lack of standardized approach to diagnose the disease, further complicated by changes in HR dynamics in the HF population, which render reference values derived from a normal population invalid. Cardiac implantable electronic devices (implantable cardioverter defibrillator; cardiac resynchronization therapy) now offer a unique opportunity to study HR dynamics and provide treatment options for CI by rate-adaptive pacing using an incorporated sensor that measures physical activity. This review provides an overview of disease mechanisms, diagnostic strategies, clinical consequences, and state-of-the-art device therapy for CI in HF.

Rate-responsive pacing and atrial high rate episodes in cardiac resynchronization therapy patients: Is low heart rate the key?

BACKGROUND

The role of atrial rate-responsive (RR) pacing in cardiac resynchronization therapy (CRT) is unclear due to the favorable effect of rate lowering in systolic heart failure. Atrial high rate episodes (AHREs) in CRT recipients are particularly worrisome since they cause loss of CRT, beyond representing a stroke risk factor.

HYPOTHESIS

The presence of an association between RR and the incidence of AHREs.

METHODS

Daily remote transmissions from 836 CRT recipients were analyzed. AHREs were classified by duration: ≥15 minutes, ≥5 hours, and ≥ 24 hours. Variables possibly associated to AHREs were included in time-dependent proportional-hazard models, averaging over 30-day periods and adjusting for main baseline variables.

RESULTS

After a median follow-up of 23.9 (12.2-36.0) months, 507 (60.6%) patients experienced at least one 15-minute AHRE. RR function was programmed in 166 (19.8%) patients and was associated with an increased AHRE occurrence rate with hazard ratio (HR) ranging from 1.45 to 1.78 for the 3 cutoffs of episode duration. The negative effect of RR function was not observed in the subset of patients with low mean heart rate (<68 bpm). Higher mean heart rates increased AHRE risk (HR:1.02, P = .01), while CRT amount decreased it (HR:0.98, P < .01). The extent of atrial pacing did not predict AHRE occurrence.

CONCLUSIONS

RR pacing in CRT recipients is associated with increased AHRE occurrence, especially when an average heart rate > 68 bpm is attained.