[Sympathetic nervous system response to exercise in patients with congestive heart failure]

The response of the sympathetic nervous system to exercise in patients with congestive heart failure was studied in 65 patients (NYHA functional class I 28, II 23, and III 14) and 22 normal subjects (N) by submaximal treadmill testing with the modified Bruce's or Sheffield's protocols. Plasma norepinephrine (NE) and epinephrine (E) levels were also measured at rest, at the end of each stage, and immediately after and 5 min after exercise. In accordance with the severity by NYHA functional class, the exercise duration became shorter and the discontinuation of exercise with symptoms occurred more frequently. Systolic blood pressure and double products (DP) at the peak exercise were significantly lower in patients with NYHA class III. NE and increments of NE increased during exercise [peak NE (pg/ml); N: 589, I: 646, II: 1253, and III: 997] and were higher at rest, during exercise and in recovery in patients with NYHA classes II and III than in the normal subjects and NYHA class I patients. E increased gradually during exercise [peak E (pg/ml); N: 60, I: 66, II: 63, and III: 66] and there were no significant differences among the four groups. A negative correlation (r = -0.53) between the peak NE and exercise duration was observed in normal subjects, while a positive correlation (r = 0.55) was observed in patients with NYHA class II. A positive correlation (r = 0.54) between DP at the peak exercise and the peak NE was observed in patients with NYHA class I, whereas a negative correlation (r = -0.46) was observed in patients with NYHA class III. The NE response in patients with NYHA classes II and III increased significantly, suggesting compensatory activation of the sympathetic nervous system for impaired cardiac function. In conclusion, the NE response to submaximal exercise testing differs in each NYHA functional class and it might be a useful indicator to evaluate cardiac function of patients with congestive heart failure.