Cardiopulmonary exercise testing
Submaximal exercise or symptom-limited exercise was selected as the exercise program, and indicators such as oxygen consumption, 12-lead electrocardiogram, and blood pressure were continuously monitored during exercise. After resting for 3 min, the patients were instructed to cycle at a speed of 55–65 rpm/min for 3 min without load, and then increase the ramp power at a speed of 10–20 week/min until the symptom limit was reached or the target exercise volume reached. The evaluation indicators were VO