Heart failure-related myopathy. Clinical and pathophysiological insights.

Aims: To evaluate the relationship of skeletal and respiratory muscular dysfunction with the degree of clinical severity, cardiac impairment and exercise intolerance in patients with chronic heart failure.

Methods And Results: Ninety-one patients (age 52.7+/-8 years) on standard therapy and in a stable clinical condition with normal nutritional status underwent evaluation of (1) clinical severity and metabolic status (NYHA class, weight, albuminaemia, natraemia, cortisol, insulin, neurohormones), (2) cardiac function (Echo, right heart catheterization), (3) exercise tolerance (peak VO(2)), (4) dynamic isokinetic forces of the quadriceps and hamstring (Cybex method), and respiratory muscle strength (maximal inspiratory and expiratory pressures). Fifty patients had a peak VO(2)<14 ml x kg(-1) x min(-1)(10.6+/-2) and 41 had values >/=14 (18.3+/-4). In the former group, leg and respiratory strength were significantly lower (extensors: 80+/-24 vs 100.9+/-22 Nm; flexors: 48.5+/-24 vs 75.3+/-22, both P<0.001; maximal expiratory pressure: 85.5+/-30 vs 104.8+/-31, P<0.01). Muscular strength was not related to indices of clinical severity, metabolic status, neurohormones or to the degree of systolic/diastolic cardiac function, but it was related to weight and age. Multivariate analysis of the peak VO(2)with clinical, haemodynamic and peripheral indicators showed weight (beta= 0.32, P = 0.007), muscular strength (beta= 0.32, P = 0.01) and NYHA class (beta= 0.31, P = 0.001) as the only independent predictors. The joint adjusted R(2)value was 0.48 (P<0.001).

Conclusion: Muscular dysfunction is part of the syndrome of heart failure. Together with symptom perception, it predicts nearly half of the variation in exercise tolerance.