ALM/BMI: A Clinically Superior Index for Identifying Skeletal Muscle Dysfunction in Patients With Heart Failure.

Abstract

Skeletal muscle wasting is critical in patients with heart failure (HF). Whereas prior studies have employed appendicular lean mass (ALM) normalized by height squared to identify low skeletal muscle mass, the potential of ALM normalized to body mass index (ALM/BMI) remains unexplored in patients with HF. In this study, we compared the use of 2 skeletal muscle mass indices in patients with HF to examine their sex-specific correlations with measures of physical capacity, quality of life, and daily physical activity. A total of 111 patients with HF underwent dual x-ray absorptiometry, physical capacity tests, and accelerometry and answered a quality-of-life questionnaire. ALM normalized by height squared and ALM/BMI indices disagreed in classifying low muscle mass (Cohen's κ, -0.008 [95% CI, -0.094 to 0.177]; P=0.93). ALM/BMI correlated well with 6-minute walking distance in women and men (R=0.67 and 0.49; P<0.001), with maximal oxygen uptake in women and men (R=0.41 and 0.48; P<0.05), and with maximal muscle strength in women and men (R=0.54 and 0.43; P<0.01). Inversely, ALM normalized by height squared did not correlate significantly with 6-minute walking distance or maximal oxygen uptake and correlated with maximal muscle strength only in men (R=0.43; P<0.001). Only ALM/BMI allowed for identification of a low-muscle-mass group characterized by poor quality of life (Minnesota Living With Heart Failure Questionnaire score of 33±21 versus 25±16; P=0.027) and less daily time spent in moderate to vigorous physical activity (8 [3-17] versus 15 [9-37] minutes; P<0.001). ALM/BMI was superior for identifying clinically significant muscle dysfunction in both female and male patients with HF.