Phase angle and functional outcomes after acute myocardial infarction

Acute myocardial infarction (AMI) remains a major cause of morbidity and mortality worldwide. Simple and non-invasive markers that reflect functional status are needed for risk stratification and rehabilitation planning. Phase angle (PhA), derived from bioelectrical impedance analysis, reflects cellular integrity and muscle quality; however, its relationship with functional outcomes after AMI remains unclear. Therefore, this study aimed to evaluate the independent associations of PhA with peak oxygen consumption (VO₂peak), skeletal muscle index (SMI), and brachial-ankle pulse wave velocity (baPWV) in patients with AMI, stratified by sex.

This cross-sectional study included 224 men and 34 women with AMI. All participants underwent bioelectrical impedance analysis, cardiopulmonary exercise testing, and measurement of baPWV and ankle-brachial index. Correlation analyses and multivariable linear regression models adjusted for demographics, comorbidities, and body composition were used to assess associations between PhA and peak oxygen consumption (VO₂peak), SMI, and arterial stiffness. Analyses were stratified by sex.

PhA was positively correlated with VO₂peak and SMI and negatively correlated with baPWV in both sexes. In multivariable models, higher PhA remained independently associated with VO₂peak (men: β = 0.623, P < 0.001; women: β = 1.070, P = 0.002) and SMI (men: β = 1.109, P < 0.001; women: β = 1.225, P < 0.001) in both men and women, while its inverse association with baPWV was significant only in men (β = -0.422, P = 0.005).

PhA was independently associated with exercise capacity and muscle mass in both sexes after AMI, whereas its association with arterial stiffness was observed only in men. This sex-specific finding should be interpreted cautiously given the limited number of female participants and warrants further investigation.