Comparison of left ventricular responses to the six-minute walk test, stair climbing, and maximal upright bicycle exercise in patients with congestive heart failure due to idiopathic dilated cardiomyopathy

Submaximal exercise tests have been advocated to assess exercise capacity in chronic heart failure, but hemodynamic responses have not been characterized. To determine left ventricular (LV) responses during submaximal exercise, the LV ejection fraction (EF) and volumes were evaluated by using an ambulatory radionuclide detector in 13 patients with idiopathic dilated cardiomyopathy during upright maximal graded bicycle exercise, stair climbing and a 6-minute walk test. The 3 tests elicited different responses in volumes and, to a lesser degree, in LVEF. The maximal bicycle exercise led to a decrease in LVEF from 22 ± 9% to 17 ± 8% (p < 0.05), with marked increases in both end-diastolic volume (EDV) (+15 ± 10%, p < 0.001) and end-systolic volume (ESV) (+23 ± 18%, p < 0.001). Stair climbing tended to reduce LVEF (from 24 ± 11% to 21 ± 10%, p = 0.05), with a lesser increase in volumes, which was more marked for ESV (+8 ± 9%, p < 0.01) than for EDV (+4 ± 4%, p < 0.01). The 6-minute walk test did not significantly change LVEF (23 ± 10% vs 22 ± 10%), but increased both EDV (+10 ± 6%, p < 0.001) and ESV (+8 ± 8%, p < 0.01) moderately and proportionally. Exercise capacity indexes (peak oxygen consumption, maximal bicycle work rate, stair climbing time, and the distance covered during the 6-minute walk test) correlated significantly with one another. There was no correlation between submaximal exercise tolerance indexes and resting or exercise LVEF. This study shows that (1) LVEF changes are inadequate to report on LV volume changes during exercise; (2) the 3 tests induce different LV volume changes; (3) the 6-minute walk test induces significant changes in LV volumes but no change in LVEF.