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

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.

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.

Closed loop stimulation reduces the incidence of atrial high-rate episodes compared with conventional rate-adaptive pacing in patients with sinus node dysfunctions

AIMS

Subclinical atrial fibrillation (AF) is associated with increased risk of progression to clinical AF, stroke, and cardiovascular death. We hypothesized that in pacemaker patients requiring dual-chamber rate-adaptive (DDDR) pacing, closed loop stimulation (CLS) integrated into the circulatory control system through intra-cardiac impedance monitoring would reduce the occurrence of atrial high-rate episodes (AHREs) compared with conventional DDDR pacing.

METHODS AND RESULTS

Patients with sinus node dysfunctions (SNDs) and an implanted pacemaker or defibrillator were randomly allocated to dual-chamber CLS (n = 612) or accelerometer-based DDDR pacing (n = 598) and followed for 3 years. The primary endpoint was time to the composite endpoint of the first AHRE lasting ≥6 min, stroke, or transient ischaemic attack (TIA). All AHREs were independently adjudicated using intra-cardiac electrograms. The incidence of the primary endpoint was lower in the CLS arm (50.6%) than in the DDDR arm (55.7%), primarily due to the reduction in AHREs lasting between 6 h and 7 days. Unadjusted site-stratified hazard ratio (HR) for CLS vs. DDDR was 0.84 [95% confidence interval (CI), 0.72-0.99; P = 0.035]. After adjusting for CHA2DS2-VASc score, the HR remained 0.84 (95% CI, 0.71-0.99; P = 0.033). In subgroup analyses of AHRE incidence, the incremental benefit of CLS was greatest in patients without atrioventricular block (HR, 0.77; P = 0.008) and in patients without AF history (HR, 0.73; P = 0.009). The contribution of stroke/TIA to the primary endpoint (1.3%) was low and not statistically different between study arms.

CONCLUSION

Dual-chamber CLS in patients with SND is associated with a significantly lower AHRE incidence than conventional DDDR pacing.

Temporal relationship between haemodynamic changes and activation of closed-loop stimulation during a tilt-induced vasovagal syncope

AIMS

A dual-chamber pacemaker with closed-loop stimulation (CLS) mode is effective in reducing syncopal recurrences in patients with asystolic vasovagal syncope (VVS). In this study, we explored the haemodynamic and temporal relationship of CLS during a tilt-induced vasovagal reflex.

METHODS AND RESULTS

Twenty patients underwent a tilt test under video recording 3.9 years after CLS pacemaker implantation. Three patients were excluded from the analysis because of no VVS induced by the tilt test (n = 1) and protocol violation (n = 2). In 14 of the remaining 17 patients, CLS pacing emerged during the pre-syncopal phase of circulatory instability when the mean intrinsic heart rate (HR) was 88 ± 12 b.p.m. and systolic blood pressure (SBP) was 108 ± 19 mmHg. The CLS pacing rate thereafter rapidly increased to 105 ± 14 b.p.m. within a median of 0.1 min [inter-quartile range (IQR), 0.1-0.7 min] when the SBP was 99 ± 21 mmHg. At the time of maximum vasovagal effect (syncope or pre-syncope), SBP was 63 ± 17 mmHg and the CLS rate was 95 ± 13 b.p.m. The onset of CLS pacing was 1.7 min (IQR, 1.5-3.4) before syncope or lowest SBP. The total duration of CLS pacing was 5.0 min (IQR, 3.3-8.3). Closed-loop stimulation pacing was not observed in three patients who had a similar SBP decrease from 142 ± 22 mmHg at baseline to 69 ± 4 mmHg at the time of maximum vasovagal effect, but there was no significant increase in HR (59 ± 1 b.p.m.).

CONCLUSION

The reproducibility of a vasovagal reflex was high. High-rate CLS pacing was observed early during the pre-syncopal phase in most patients and persisted, although attenuated, at the time of maximum vasovagal effect.

REGISTRATION

ClinicalTrials.gov identifier: NCT06038708.