[Skeletal and respiratory muscle strength in chronic heart failure]

The aim of this study was to investigate limb and respiratory muscle strength in chronic heart failure (CHF).

Our study population consisted of 45 male CHF patients, 25 in NYHA Class II and 20 in NYHA Class III, and 22 male post-MI patients without left ventricular dysfunction (LVEF > 50%). All patients underwent assessment of respiratory muscle strength by maximal inspiratory (MIP) and expiratory (MEP) pressures, of handgrip force and peak torque developed during isokinetic Knee extension (EX) (quadriceps) and flexion (hamstring) at 120 degrees/sec.

CHF patients showed a significant decrease in all limb and respiratory muscle strength compared to control patients. Moreover, NYHA Class III patients showed significantly reduced values of MIP, handgrip, and EX forces, as well as significantly reduced exercise tolerance in terms of METS (2.8 +/- 0.9 vs 4.4 +/- 1.2, p < .05) and anaerobic threshold level (9.4 +/- 3 vs 12.8 +/- 1.7 mlO2/Kg, p < .05), as compared to those patients in NYHA Class II, while no significant differences were observed in LVEF, cardiac index and pulmonary capillary wedge pressures. Weak, but significant (p < .05) were the correlations between limb muscle and respiratory muscle strength. No correlations were found between muscle force and hemodynamic parameters. Significant correlations (from p < .05 to p < .0001) were found among exercise tolerance and limb muscle strength, but not between exercise tolerance and respiratory muscle strength. In summary: 1) respiratory and skeletal muscle strength is impaired in CHF; 2) respiratory and limb muscle strength reductions are partially related to each other; 3) the degree of central hemodynamic impairment is not correlated with muscle force. Deconditioning could be a major determinant of skeletal but not respiratory muscle weakness. Other factors link limb and respiratory weakness in CHF.