Relationship between Exercise Tolerance and Respiratory Pattern and Muscular Strength of Legs in Patients with Chronic Heart Failure

The main symptom of chronic heart failure (CHF) is dyspnea and leg fatigue on exercise, demonstrating a decrease in exercise capacity. However, the precise mechanisms of these symptoms are not fully understood. The existence of a relationship between exercise tolerance and respiratory pattern and muscular strength of legs in patients with CHF has not been demonstrated. In this study, therefore, we measured these parameters to clarify the factors which relate to exercise tolerance in CHF patients. Subjects were fifty-four consecutive patients (37 men and 17 women, mean age 53 years) with CHF who underwent cardiopulmonary exercise testing at our hospital from February 1999 to September 2000. Peak oxygen uptake (peak VO2) and respiratory pattern (TV/RR; tidal volume/respiratory rate) were evaluated. The strength of quadriceps was also measured. The respiratory pattern was weak but significantly correlated with peak VO2 (r=0.27, p<0.05). Maximal isometric strength of quadriceps showed a tendency to correlate with peak VO2 (r=0.25, p=0.06). These findings suggest that exercise intolerance, seen in these CHF patients, is related to both respiratory pattern and the maximal muscular strength of legs.