Ventilatory responses to exercise in patients with asymptomatic left ventricular dysfunction

Purpose: Based on reports that patients with severe left ventricular (LV) d ysfunction have a greater ventilatory response to effort than healthy peopl e, we evaluated the ventilatory responses to effort of patients with corona ry artery disease and various degrees of LV impairment before and after 6 m onths of exercise training in a community-based cardiac rehabilitation prog ram. Methods: Out of 171 patients consecutively referred for cardiac rehabi litation, 102 were enrolled in the study. Fifteen patients were excluded be cause of lung disease and 54 because of poor adherence to the exercise prog ram. Patients were divided into three groups according to their ejection fr action (EF): Group I (G1) included 63 patients with EF greater than or equa l to 50%, Group 2 (G2) included 21 patients with EF greater than or equal t o 35 and < 50% and group 3 (G3) included 18 patients with EF < 35%. Peak ox ygen uptake, minute ventilation ((V) over dot(E)), and minute carbon dioxid e production ((V) over dot CO2) 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 (V) over dot (E)/(V) over dot CO2 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 (V) over dot(E) to (V) ov er dot CO2 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 a ny group. Conclusions: Patients with severe LV dysfunction had a greater ve ntilatory response to exercise than those with moderately impaired or norma l LV function. Exercise training increased the effort tolerance of all pati ents irrespective of their degree of LV dysfunction but failed to reduce th e higher ventilatory responses to effort of patients with EF below 35%.