Serial Assessment Of The Cardiorespiratory Fitness Vital Sign: Prognostic Significance One Year Post Cardiac Rehabilitation

Abstract

Cardiorespiratory fitness (CRF) consistently demonstrates robust prognostic value in apparently healthy individuals and in those at risk for or diagnosed with one or more chronic conditions. While CRF at baseline and immediately following cardiac rehabilitation (CR) hold prognostic value, little is known about the significance of serial CRF assessments over a prolonged period. PURPOSE: Assess the prognostic utility of serial CRF assessments in patients completing CR. METHODS: 3,185 patients (mean age = 62 ±10 years, 82% male) with cardiovascular disease (CVD) that were referred to and completed a 12-week exercise-based CR program were included. All patients completed a symptom-limited treadmill exercise test at baseline, immediately following CR and at 1-year follow-up. Peak metabolic equivalents (METs) were determined at each exercise test from treadmill speed and grade. The difference between peak METs at baseline and immediately post CR and between baseline and 1-year post CR were also calculated. Patients were subsequently tracked for all-cause mortality. RESULTS: 206 subjects died during the tracking period (mean tracking = 79 ±34 months). Peak METs at baseline (Mean = 7.7 ±2.0 METs, HR: 0.66, 95% CI: 0.62-0.71, p<0.001), immediately following CR (Mean = 8.7 ±2.0 METs, HR: 0.65, 95% CI: 0.60-0.69, p<0.001) and 1-year post CR (Mean = 8.6 ±2.2 METs HR: 0.65, 95% CI: 0.61-0.69, p<0.001) were all significant predictors of survival. The mean change in peak METs from baseline to immediate post CR (0.88 ±1.4 METs) and from baseline to 1-year post CR (0.88 ±1.3 METs) was significant (p<0.001). However, only the change in peak METs from baseline to 1-year post CR was a significant predictor of survival (HR: 0.73, 95% CI: 0.66-0.80, p<0.001). CONCLUSIONS: The current findings again demonstrate the prognostic significance of the CRF vital sign in patients with CVD undergoing CR. Our results indicate continued serial assessment of the CRF, in this analysis 1-year following completion of CR, provides important prognostic information. In particular, maintenance of CRF improvement following CR over the long-term is clinically important and should be monitored.