Background: Cardiac resynchronization therapy (CRT) improves functional capacity in heart failure patients. This study aimed to prospectively analyze long-term device-based monitoring of physical activity in patients undergoing CRT.
Methods and results: The Activity Log Index (ALI), calculated by CRT devices, represents the percentage of time when acceleration exceeds a threshold and monitors the physical activity. Data from 178 CRT patients (New York Heart Association III 91%, left ventricular ejection fraction 21+/-6%, left ventricular end-diastolic diameter 69+/-9 mm, QRS 159+/-27 ms, sinus rhythm 81%) were retrieved. The ALI increased from a baseline value of 3.6+/-2.0 to 11.2+/-4.6 (p<0.005) 104 weeks after initiation of CRT. A plateau was reached at approximately 12 weeks and thereafter ALI remained stable for up to 2 years. The magnitude of the changes in ALI was similar in patients with different etiologies and underlying rhythms. Despite similar values at baseline, elderly patients (>or=65 years) exhibited significantly lower ALI values than younger patients during the follow-up and at the plateau (9.5+/-4.2 vs 13.3+/-4.8, p<0.001).
Conclusions: Device-based monitoring of physical activity in CRT patients is feasible. CRT resulted in a large and long-term increase in physical activity.