Ventilatory and heart rate responses after exercise in chronic cardiac failure

1. To determine if the recovery period after exercise is abnormal in chronic cardiac failure, we studied 15 patients with stable chronic cardiac failure, and 14 normal subjects during and after symptom-limited maximal treadmill exercise. 2. In patients, O2 consumption fell exponentially from 16.8 (13.7-20.0) ml min-1 kg-1 at peak exercise to 6.0 (5.2-6.7) ml min-1 kg-1 at 3 min of recovery and in control subjects it fell from 30.2 (27.0-33.5) ml min-1 kg-1 to 6.7 (5.9-7.4) ml min-1 kg-1 (mean and 95% confidence intervals). The associated decay constants were slower in patients [0.70 (0.58-0.83) min-1 versus 0.93 (0.81-1.05) min-1 in control subjects (P < 0.01, t-test)]. 3. CO2 consumption kinetics displayed similar abnormalities [(k: 0.55 (0.41-0.69) min-1 versus 0.71 (0.59-0.83) min-1, P < 0.05)] and heart rate kinetics showed a similar trend [(k: 0.53 (0.33-0.74) min-1 versus 0.76 (0.62-0.89) min-1, P = 0.08]. 4. We conclude that patients with cardiac failure recover more slowly from exercise than normal subjects, and that this may further impair their ability to perform exercise, with consequent effect on quality of life.