Endurance capacity and muscle strength as a composite indicator of physical reserve in men with systolic heart failure

INTRODUCTION: Reduced composite physical reserve may coexist with systolic heart failure (HF). OBJECTIVES: To evaluate clinical differences among patients stratified by composite physical reserve in the 6-minute walk test (6MWT) and maximal handgrip strength (MHG), and to identify clinical correlates of reduced physical function. PATIENTS AND METHODS: This post hoc analysis included 332 men from a prospective cohort of outpatients with stable HF (LVEF <50%) who completed both tests. Patients were stratified into three categories based on median splits of 6MWT (480 m) and MHG (40 kg) to define composite physical reserve, i.e., (1) both 6MWT and MHG above group medians; (2) either 6MWT or MHG at or below the median; or (3) both at or below. Clinical characteristics were compared using ANCOVA (estimated marginal means and standard errors) and logistic regression (odds ratios [ORs]), adjusted for age, diabetes, and smoking. RESULTS: Category 3 patients had significantly higher resting heart rate (72.2 [0.96] vs. 64.4 [1.1] bpm, P <0.001), serum creatinine (1.27 [0.03] vs. 1.16 [0.04] mg/dL, P <0.001), and NT-proBNP (log10 3.09 [0.05] vs. 2.76 [0.05] pg/mL, P <0.001) than Category 1 patients. Each one-category increase was associated with greater odds of NYHA class 3-4 (OR: 2.60), resting HR >75 bpm (OR: 2.44), chronic AF (OR: 1.53), increased diuretics (OR: 1.53) and digoxin (OR: 1.99) use. CONCLUSIONS: Lower combined endurance and strength identify HF patients with a more severe clinical phenotype and greater treatment intensity. This functional performance-based categorization may offer a simple, promising tool for clinical phenotype stratification in systolic HF.