Accelerometer-derived circadian rhythm parameters are associated with risk of malignant ventricular arrhythmias in implantable cardioverter defibrillator patients

Emerging evidence suggests that circadian rhythms play a critical role in electrophysiology and may influence the risk of cardiac arrhythmias. However, it remains unclear whether disruptions in circadian rhythms are associated with ventricular arrhythmias. The circadian rest-activity rhythm (CRAR) serves as a behavioural marker of circadian function and can be measured by a wearable accelerometer. This study investigates the association between CRAR parameters and risk of appropriate implantable cardioverter-defibrillator (ICD) therapy for malignant ventricular arrhythmias.

To investigate whether CRAR disruptions, measured by a wrist-worn accelerometer, are associated with increased risk of ventricular arrhythmias in ICD patients.

This is a sub-analysis of a multicentre, prospective study, conducted at two European centres. Patients with an ICD were enrolled and wore wristband accelerometers for 180 days. Raw accelerometer data during the first seven days of continuous monitoring was used. This high-resolution data allows for precise characterization of rest and activity patterns across the 24-hour cycle. Raw data were converted to activity intensity per minute and used to derive CRAR metrics (Figure 1), including parametric metrics from a cosinor model (amplitude, mesor, acrophase) and non-parametric metrics: mean activity during the most active 10 hours (M10) and least active 5 hours (L5), relative amplitude, interdaily stability, and intradaily variability. Variables were compared between patients who did and did not receive appropriate ICD therapy. Associations between CRAR metrics and the risk of ICD therapy were assessed using Cox regression, adjusted for age, BMI, season of measurement, heart failure etiology (HFrEF or HFpEF), and ICD implantation indication (secondary or primary prevention).

Among 280 included participants (mean age 63 ± 10 years, 81% male), 51 (18%) received appropriate ICD therapy over one-year follow-up. Baseline demographics were similar between groups, while amplitude, relative amplitude, and interdaily stability were significantly lower in the group that received ICD therapy. In the adjusted Cox model, amplitude (hazard ratio (HR): 0.68, 95% confidence interval (CI): 0.51 – 0.91), relative amplitude (HR: 0.73, 95% CI: 0.57 – 0.93) and intradaily variability (HR: 1.31, 95% CI: 1.01 – 1.69) were significantly associated with the risk of receiving appropriate therapy, Figure 2.

Disruptions in circadian rest-activity patterns, particularly a decreased amplitude, reflecting lower daytime activity and increased nighttime activity, are associated with a higher risk of appropriate ICD therapy. An increased intradaily variability, reflecting more fragmented activity patterns, was also linked to elevated arrhythmic risk. These results highlight the potential of using circadian rhythm metrics for identification of high-risk individuals and personalizing ICD care.

Overview of CRAR parameters