Ventilatory responses to exercise in patients with asymptomatic left ventricular dysfunction. Med. Sci. Sports Exerc., Vol. 31, No. 7, pp. 942-948, 1999.
Purpose: Based on reports that patients with severe left ventricular (LV) dysfunction have a greater ventilatory response to effort than healthy people, we evaluated the ventilatory responses to effort of patients with coronary artery disease and various degrees of LV impairment before and after 6 months of exercise training in a community-based cardiac rehabilitation program.
Methods: Out of 171 patients consecutively referred for cardiac rehabilitation, 102 were enrolled in the study. Fifteen patients were excluded because of lung disease and 54 because of poor adherence to the exercise program. Patients were divided into three groups according to their ejection fraction (EF): Group 1 (G1) included 63 patients with EF ≥ 50%, Group 2 (G2) included 21 patients with EF ≥ 35 and < 50% and group 3 (G3) included 18 patients with EF < 35%. Peak oxygen uptake, minute ventilation (V̇E), and minute carbon dioxide production (V̇CO2) were measured before and after training in all participants.
Results: All groups showed a significant increase in peak oxygen uptake and treadmill time after training (G1: P = 0.0001 and P = 0.0001; G2: P = 0.0001 and P = 0.001; G3: P = 0.01 and P = 0.01; respectively). Patients in G3 had a significantly higher V̇E/V̇CO2 ratio than patients in G2 and G1 at 9 min and peak exercise, before (9 min: P = 0.046 and P = 0.025, peak: P = 0.024 and P = 0.002, respectively) and after training (9 min: P = 0.011 and P = 0.005, peak: P = 0.001 and P = 0.0001, respectively). The slope of the relation V̇E to V̇CO2 was significantly higher in G3 patients than in those in G2 and G1 (P = 0.0001, respectively) and was not reduced by exercise training in any group.
Conclusions: Patients with severe LV dysfunction had a greater ventilatory response to exercise than those with moderately impaired or normal LV function. Exercise training increased the effort tolerance of all patients irrespective of their degree of LV dysfunction but failed to reduce the higher ventilatory responses to effort of patients with EF below 35%.