Purpose: The purpose of this pilot study was to examine the concurrent validity of daily activity data from Medtronic implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT) devices and the Actigraph GT3X triaxial accelerometer in patients with heart failure (HF).

Methods: Analysis of the first 16 subjects with HF completing 3-month follow-up in a randomized trial with a secondary purpose to examine concurrent validity of Medtronic ICD/CRT device-based daily activity and the following Actigraph GT3X parameters: hours of activity per day, activity counts, and steps per day. Daily activity data were measured at baseline and 3-month follow-up and analyzed using Pearson correlation coefficients to measure intraindividual correlations and Bland-Altman plots to examine agreement between devices.

Results: Moderate-to-strong, statistically significant correlations were found between the Medtronic ICD/CRT and Actigraph GT3X devices for all parameters measured. The Bland-Altman plots revealed approximately 0.80 hours less activity per day measured by the Medtronic ICD/CRT compared with the Actigraph GT3X. Strong agreement for the 7-day average and moderate-to-strong agreement for all daily observations for hours of activity per day was found between both devices. Similarly, there was moderate-to-strong agreement for change in hours of activity and steps per day between baseline and 3-month follow-up.

Conclusions: The Medtronic ICD/CRT devices seem to be a sufficiently accurate, responsive measure of daily activity in patients with HF when compared with the Actigraph GT3X.