Accelerometer-Measured Physical Activity After Mitral Valve Surgery: An Analysis of the UK Mini Mitral Randomized Controlled Trial

Abstract

BACKGROUND: Wearable accelerometer devices measure free-living physical activity and sleep without relying on self-reports. Their utility to measure and compare recovery of physical function after cardiac surgery procedures has not been previously studied in the setting of a randomized controlled trial. METHODS: Data were collected during the UK (United Kingdom) Mini Mitral trial, in which patients were randomized to undergo either a sternotomy or a minimally invasive thoracoscopically guided right minithoracotomy procedure (Mini) for mitral valve repair. This is a secondary analysis of the trial data using a different primary end point. Patients wore a wrist-worn triaxial accelerometer on their nondominant wrist for 24 hours over a 7-day period before surgery and at 6, 12, 18, 24, 38, and 52 weeks after surgery. Accelerometer outcomes included the change from baseline to 52 weeks in total activity counts and time spent in moderate-to-vigorous physical activity, light physical activity, and sedentary time. Time spent asleep and sleep efficiency were also captured. Accelerometry data were processed and analyzed by researchers blinded to the surgical approach. RESULTS: A total of 230 patients (115 in each trial arm) provided valid accelerometry data. There were significant differences between arms in total activity counts; the mean difference was 26 744 (95% CI, 9085–44 403; P =0.003) at 6 weeks and 26 060 (95% CI, 6971–45 149; P =0.008) at 18 weeks, both favoring Mini. Time spent in moderate-to-vigorous physical activity also favored the Mini arm at 6 and 18 weeks, with mean differences of 15 (95% CI, 5.7–24; P =0.001) and 9.9 (95% CI, 0.31–20; P =0.043) minutes per day, respectively. Those in the Mini arm also had significantly lower sedentary time (at 12, 18, and 24 weeks) and spent more time in light physical activity (at 18 weeks) than those in the sternotomy arm. There were no differences in sleep duration between arms at any time point, although those in the Mini arm had higher sleep efficiency than those in the sternotomy arm at 12 weeks. CONCLUSIONS: This analysis from the UK Mini Mitral trial suggests that wearable accelerometer devices can be used to compare recovery after surgical procedures. The data support an overall decline from baseline activity to 52 weeks in patients undergoing a sternotomy and an earlier recovery of physical activity after a minimally invasive thoracoscopically guided right minithoracotomy approach.