Predictive value of device-derived activity level for short-term outcomes in MADIT-CRT.

Background: There are limited data on the prognostic importance of declining activity level in patients with heart failure.

Objective: We aimed to assess the association of reduced activity level with adverse cardiovascular outcomes in the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT).

Methods: Final device interrogations from patients enrolled in the MADIT-CRT with cardiac resynchronization devices capable of recording percent daily activity level were assessed. To determine temporal change, standardized activity levels (SALs) comparing each week to the monthly activity 3 months prior were obtained. Death, heart failure events (HFEs)/death, and ventricular tachyarrhythmias (VTAs)/death were the primary end points of this study.

Results: The average absolute activity level and SAL of the final week prior to death or end of study were significantly lower in patients who died compared with those in patients who did not. The total cohort (N = 1008) was further randomized into 2 subgroups to identify (group 1) and validate an optimal threshold (group 2). Patients with >40% reduced SAL had a significantly increased 77-day short-term cumulative incidence of death (P = .0006), HFE/death (P < .0001), or VTA/death (P = .0248). After adjustment for clinical covariates, these patients remained at an increased risk for death (hazard ratio [HR], 2.7; 95% confidence interval [CI], 1.5-4.9; P = .001), HFE/death (HR, 2.7; 95% CI, 1.8-3.9; P ≤ .001) and VTA/death (HR, 1.9; 95% CI, 1.31-2.6; P = .001). A decline in SAL following a nonfatal VTA and HFE was also associated with an increased probability of death.

Conclusions: Decline in activity level is a short-term predictor for adverse cardiovascular events in patients with mild to moderate heart failure undergoing cardiac resynchronization.