Cross-Sectional Associations Between Skeletal Muscle Measurements, Myostatin, and MicroRNA-133a in Heart Failure Patients Undergoing Cardiac Rehabilitation

Background: Skeletal myopathy is a common complication of heart failure (HF), contributing to exercise intolerance and impaired physical function. This study explores the relationship between practical skeletal muscle measurements and key biomarkers in HF patients undergoing cardiac rehabilitation. Methods: Sixty-nine stable chronic HF patients participated in a 3-month phase II cardiac rehabilitation program. Physical examinations, including the 6-Minute Walk Test (6MWT), chest expansion, inspiratory diaphragm thickness, and handgrip strength, were conducted. Blood samples were analyzed for myostatin and miRNA-133a. Data were analyzed using paired t-tests, Wilcoxon tests, Chi-square/Fisher’s exact tests, and correlation analyses. Results: Significant improvements were observed in 6MWT distance, chest expansion, and inspiratory diaphragm thickness following rehabilitation (p < 0.001). Handgrip strength also significantly improved post-rehabilitation. Myostatin and miRNA-133a levels did not change significantly post-rehabilitation. However, exploratory cross-sectional analysis revealed trends suggesting that lower myostatin levels correlated with better endurance (p = 0.036), while higher myostatin levels were also observed in patients with better 6MWT performance (p = 0.014). Higher miRNA-133a levels were potentially associated with better overall fitness, including endurance and respiratory function (p < 0.05). Conclusions: Readily performed physical assessments can serve as clinical indicators of the systemic impact of HF on skeletal muscle. The study highlights the importance of evaluating extracardiac function in HF patients, demonstrating potential exploratory associations between physical function and key biomarkers.