Accelerometer-Measured Daily Activity in Heart Failure with Preserved Ejection Fraction: Clinical Correlates and Association with Standard Heart Failure Severity Indices

Background - Daily physical activity assessed by accelerometers represents a novel method to assess the impact of interventions on heart failure (HF) patients' functional status. We hypothesized that daily activity varies by patient characteristics and correlates with established measures of HF severity in HF with preserved ejection fraction. Methods and Results - In this ancillary study of the NEAT-HFpEF trial (Nitrate's Effects on Activity Tolerance in HF With Preserved Ejection Fraction), average daily accelerometer units (ADAU) and hours active per day were assessed during a 14-day period before starting isosorbide mononitrate or placebo (n=110). Baseline ADAU was negatively associated with age, female sex, height, and body mass index, and these variables accounted for 28% of the variability in ADAU (P<0.007 for all). Adjusting for these factors, patients with lower ADAU were more likely to have had an HF hospitalization, orthopnea, diabetes mellitus and anemia, be treated with β-blockers, have higher ejection fraction, relative wall thickness and left atrial volume, and worse New York Heart Association class, HF-specific quality of life scores, 6-minute walk distance, and NT-proBNP (N-terminal pro-B-type natriuretic peptide; P<0.05 for all). Associations between hours active per day and clinical characteristics were similar. Relative to baseline, there were no significant associations between changes in ADAU or hours active per day and changes in standard functional assessments (New York Heart Association, quality of life, 6-minute walk distance, and NT-proBNP) with isosorbide mononitrate. Conclusions - Daily activity is a measure of HF-related and global functional status in HF with preserved ejection fraction. As compared with intermittently assessed standard HF assessments, change in daily activity may provide unique information about the impact of HF interventions on functional status.