Impact of closed loop stimulation on prognostic cardiopulmonary variables in patients with chronic heart failure and severe chronotropic incompetence: a pilot, randomized, crossover study

The clinical role of closed loop stimulation pacemakers in the treatment of patients with sinus node dysfunction: a review

Sinus bradycardia, sinoatrial block, sinus arrest, and bradycardia-tachycardia syndrome are manifestations of intermittent or persistent sinus node dysfunctions (SNDs). SND is classified as intrinsic, when related to an anatomic disease of sinoatrial cells, or extrinsic, when bradycardia is caused by inappropriate vagal outflow. Chronotropic incompetence is often associated with SND, especially in elderly patients. When symptoms are related to SND, pacemaker implantation is the recommended therapy, and rate-adaptive pacing modes are often preferred in cases of chronotropic incompetence. Closed-Loop Stimulation (CLS) is a rate-adaptive system based on continuous evaluation of contractility and contraction speed through the analysis of right-ventricular unipolar impedance trends during the systole of each cardiac cycle. An increase in contractility or contraction speed modifies the impedance trends, to which the CLS algorithm responds by adapting the pacing rate, and thereby heart rate and cardiac output. Therefore, CLS is integrated into the autonomic mechanisms of cardiac output regulation. This feature has drawn interest in the use of CLS in several forms of SND, from the treatment of intrinsic bradycardias to the prevention of vasovagal syncope and device-detected atrial fibrillation. We will examine the working principle of CLS and review the results of recent clinical investigations.

Improving lung function capacity in patients with chronotropic incompetence using closed loop stimulation: A randomized crossover study

BACKGROUND

Chronotropic incompetence (CI) severely limits exercise tolerance due to impaired heart rate responses. This study investigated whether pacemaker with closed-loop stimulation (DDD-CLS) pacing, which provides rate acceleration in response to exertion, could enhance lung function and cardiopulmonary capacity compared pacemaker without CLS pacing in patients with CI.

METHODS

This randomized crossover trial included 32 patients with CI who were compared to each CLS and DDD pacing over 2 months. Spirometry was used to assess the forced vital capacity (FVC). Cycling-based cardiopulmonary exercise testing (CPET) measured peak oxygen uptake (peak VO2).

RESULTS

DDD-CLS pacing yielded significantly higher FVC (2.2 ± 0.8 L) versus DDD pacing (2.0 ± 0.7 L), p = 0.036, a 3.2% improvement. Moreover, those in the DDD-CLS mode showed a significantly higher FEV1 of 1.8 ± 0.6 L compared to the DDD mode of 1.7 ± 0.5 L (p = 0.03). Compared with DDD pacing, DDD-CLS pacing also achieved superior peak VO2 (14.9 ± 4.0 vs 12.2 ± 3.7 mlO2/kg/min, p < 0.001) and peak heart rate (106.9 ± 9.7 vs 98.3 ± 19.8 bpm, p = 0.013). DDD-CLS and DDD pacing modes showed significant correlations between FVC and peak VO2 and between peak VO2 and peak heart rate during CPET.

CONCLUSIONS

Compared with DDD mode, DDD-CLS pacing provided physiological chronotropic support to improve cardiopulmonary function during exertion, which enhanced lung capacity in patients with CI.

Effectiveness of rate-adaptive pacing on patients with chronotropic incompetence: Systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Rate-adaptive pacing (RAP) complements heart rate (HR) responses in patients with cardiac pacing devices and chronotropic incompetence, although improvements in exercise capacity have varied across reported studies. The purpose of this study was to evaluate the effectiveness of the RAP mode across different clinical settings.

METHODS

A systematic review and meta-analysis were conducted according to PRISMA guidelines. MEDLINE and EMBASE databases were searched through May 2024. Randomized controlled trials comparing RAP-on with RAP-off modes in patients with chronotropic incompetence were included. Outcomes related to exercise capacity, such as peak oxygen uptake (VO2), exercise duration, and patient-reported outcomes (PROs), were analyzed.

RESULTS

Twelve trials with a total of 1199 patients were included. The meta-analysis showed that RAP-on significantly improved peak VO2 (mean difference [MD]: 1.35 ml/kg/min, 95 % confidence interval [CI]: 0.47 to 2.23) and exercise duration (MD:0.74 min, 95 % CI: 0.14 to 1.33) with augmenting peak HR (MD: 19 bpm, 95 % CI: 13 to 26) during cardiopulmonary exercise tests. The effectiveness of RAP on exercise capacity blunted particularly in patients with heart failure (HF) (MD: 0.36 ml/kg/min, 95 % CI: -0.88 to 1.60) compared with those without HF (MD: 1.95 ml/kg/min, 95 % CI: 0.66 to 3.23). PROs showed no significant improvement with RAP-on except for one study including non-HF.

CONCLUSIONS

RAP-on mode significantly enhances exercise capacity in patients with chronotropic incompetence, however, the benefits are less pronounced in patients with concomitant HF. In patient with HF, careful assessment is crucial to identify potential need for advanced therapeutic approach following the RAP-on pacing.

Effect of rate-adaptive atrial support compared to VDD pacing in cardiac resynchronization therapy recipients: A randomized cross-over study

BACKGROUND

Cardiac resynchronization therapy (CRT) is a cornerstone treatment for heart failure, yet the optimal pacing mode remains uncertain. This study investigates the impact of DDDR (rate-adaptive atrial support) versus VDD pacing modes on functional capacity and echocardiographic outcomes in patients with CRT-defibrillators.

METHODS

In a multicenter, double-blind, crossover trial, 26 sinus rhythm patients undergoing CRT-defibrillator implantation were randomized to DDDR at 60 beats-per-minute or VDD at 30 beats-per-minute. Each pacing mode was maintained for 6 months (period 1), followed by crossover to the alternate programming for additional 6 months (period 2). Distance covered in the 6-minute walk test (6MWT) and echocardiographic parameters were evaluated at baseline and after each period.

RESULTS

The proportion of CRT responders was 73% at 6 months and 79% at 12 months. DDDR pacing yielded a median atrial pacing percentage of 55% (interquartile range, 48%-71%). No significant difference was found between DDDR and VDD modes in 6MWT distance (448 m [369-538] vs. 428 m [360-535], P = .71). The sequence of pacing modes was also not significant (P = .17), while the study period (P = .03) and the distance covered at baseline (P < .01) were positively correlated with the distance walked at follow-up. Echocardiographic parameters, including left ventricular ejection fraction and ventricular volumes, showed no significant differences between the pacing modes.

CONCLUSIONS

In this cohort, rate-adaptive atrial support did not offer any advantage over VDD pacing in terms of functional capacity or echocardiographic response. The findings support the recommendation to maximize intrinsic sinus rhythm sensing in CRT devices.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT06592690.

Effect of Exercise-Based Cardiac Rehabilitation on Patients With Chronic Heart Failure After Transcatheter Aortic Valve Replacement: A Randomized Controlled Trial

PURPOSE

The objective of this study was to assess the effect of exercise-based cardiac rehabilitation (CR) with individualized exercise prescription in patients with chronic heart failure (HF) undergoing transcatheter aortic valve replacement (TAVR) in a randomized controlled trial.

METHODS

A total of 60 patients with chronic HF who received TAVR treatment were randomly divided into the control group (n = 30) and exercise training (ET) group (n = 30). The control group was treated with conventional rehabilitation, and the ET group was given personalized exercise-based CR based on a cardiopulmonary exercise test (CPX). The CPX parameters, echocardiography, 6-minute walk test distance, and quality of life were evaluated in the two groups.

RESULTS

All patients who completed symptom-restricted CPX showed no complications. After the 12-week rehabilitation period, the levels of anaerobic threshold, peak oxygen uptake, peak oxygen pulse, peak power, left ventricular ejection fraction, and 6-minute walk test distance in the ET group were significantly higher than those in the control group ( P  < .05). Scores on the Minnesota Life with Heart Failure Questionnaire in the ET group were lower than those in the control group ( P < .05).

CONCLUSION

Exercise-based CR significantly improves cardiopulmonary function, exercise tolerance, and quality of life in patients with chronic HF who undergo TAVR.

Sigmoidal heart rate response pattern during exercise in patients with chronic heart failure

Detailed heart rate (HR) response patterns during exercise in patients with heart failure (HF) and sinus rhythm remain uncertain. We screened consecutive patients with HF who underwent cardiopulmonary exercise tests at a large academic center from November 2013 to July 2023. HR response during exercise was statistically classified using logistic differential equation models. A total of 99 patients were included. Of them, 75 patients were assigned to "sigmoidal pattern" and the other 24 to "exponential pattern." Patients with the sigmoidal pattern were older and exhibited higher plasma B-type natriuretic peptide levels. Increases in HR and oxygen consumption (V̇o2)/kg up to the anaerobic threshold level were not different between both patterns. However, beyond the threshold, the sigmoidal pattern group showed no further increase in HR and significantly lower V̇o2/kg than their counterparts (interactions for P < 0.001). HR response during exercise in patients with heart failure and sinus rhythm was categorized into two unique groups: sigmoidal and exponential patterns. More detailed clarification of the sigmoidal pattern, potentially indicating sinus node dysfunction, should offer new clinical insights for chronotropic incompetence.NEW & NOTEWORTHY Heart rate response patterns can be classified into two groups among patients with chronic heart failure reaching maximal exertion: sigmoidal and exponential.

Enhancement of bicycle exercise capacity in patients with chronotropic incompetence through closed-loop stimulation: a randomized crossover trial

AIMS

This study aimed to investigate the effectiveness of closed-loop stimulation (CLS) pacing compared with the traditional DDD mode in patients with chronotropic incompetence (CI) using bicycle-based cardiopulmonary exercise testing (CPET).

METHODS AND RESULTS

This single-centre, randomized crossover trial involved 40 patients with CI. Patients were randomized to receive either DDD-CLS or DDD mode pacing for 2 months, followed by a crossover to the alternative mode for an additional 2 months. Bicycling-based CPET was conducted at the 3- and 5-month follow-up visits to assess exercise capacity. Other cardiopulmonary exercise outcome measures and health-related quality of life (QoL) were also assessed. DDD-CLS mode pacing significantly improved exercise capacity, resulting in a peak oxygen uptake (14.8 ± 4.0 vs. 12.0 ± 3.6 mL/kg/min, P < 0.001) and oxygen uptake at the ventilatory threshold (10.0 ± 2.2 vs. 8.7 ± 1.8 mL/kg/min, P < 0.001) higher than those of the DDD mode. However, there were no significant differences in other cardiopulmonary exercise outcome measures such as ventilatory efficiency of carbon dioxide production slope, oxygen uptake efficiency slope, and end-tidal carbon dioxide between the two modes. Patients in the DDD-CLS group reported a better QoL, and 97.5% expressed a preference for the DDD-CLS mode.

CONCLUSION

DDD-CLS mode pacing demonstrated improved exercise capacity and QoL in patients with CI, highlighting its potential as an effective pacing strategy for this patient population.

Relationships among norepinephrine levels, exercise capacity, and chronotropic responses in heart failure patients

In heart failure (HF) patients, the pathophysiological mechanisms of severe exercise intolerance and impaired exercise capacity are related to both central and peripheral abnormalities. The central abnormalities in HF patients include impaired cardiac function and chronotropic incompetence (CI). Indeed, CI, the inability to adequately increase heart rate (HR) from rest to exercise often exhibited by HF patients, is related to activation of the sympathetic nervous system (SNS) yielding a rise in circulating norepinephrine (NE). CI may result from downregulation of β-adrenergic receptors, β-blocker usage, high baseline HR, or due to a combination of factors. This paper discusses the role of elevated NE in altering chronotropic responses in HF patients and consequently resulting in impaired exercise capacity. We suggest that future research should focus on the potential treatment of CI with rate-adaptive pacing, using a sensor to measure physical activity, without inducing deleterious hormonal activation of the sympathetic system.

Closed loop stimulation in patients with chronic heart failure and severe chronotropic incompetence: Responders versus non-responders

BACKGROUND

Clinical effects of rate-adaptive pacing (RAP) are unpredictable and highly variable among cardiac resynchronization therapy (CRT) patients with chronotropic incompetence. Physiologic sensors such as Closed Loop Stimulation (CLS), measuring intracardiac impedance changes (surrogate for ventricular contractility), may add clinical benefit and help identify predictors of response to RAP. The objective of the present BIOlCREATE study subanalysis was to identify criteria for selection of CRT patients who are likely to respond positively to CLS-based RAP.

METHODS

In the randomized, crossover BIO|CREATE study, CRT patients with severe chronotropic incompetence and NYHA class II/III were randomized to CLS with conventional upper sensor rate programming or to no RAP for 1 month, followed by crossover for another month. At 1-month and 2-month follow-ups, patients underwent treadmill-based cardiopulmonary exercise test. Positive CLS response was defined as a ≥ 5% reduction in ventilatory efficiency slope. Eight of 17 patients (47%) were CLS responders. In this subanalysis, we compared responders and non-responders to explore outcomes, mechanisms, and predictors.

RESULTS

All cardiopulmonary variables, health-related quality of life, patient activity status, and NT-proBNP concentration showed favorable trend in CLS responders and unfavorable trend in non-responders, underlining the need to find predictors. Following all analyses, we recommend CLS in heart failure patients with improved left ventricular ejection fraction (LVEF >40%, after a ≥ 10-point increase from a CRT-pre-implant value of ≤40%), corresponding to 'HFimpEF' in the universal classification system.

CONCLUSION

HFimpEF patients are likely to benefit from CLS-based RAP, in contrast to 'HFrEF' (heart failure with reduced LVEF [≤40%]).