Reversal of periodic breathing after aerobic training in heart failure

To the Editors: A 58-yr-old male was referred for participation in a cardiac rehabilitation programme. He had a long-term history of hypertensive cardiomyopathy and systolic dysfunction and was clinically stable, being treated with β-blocker carvedilol, losartan, digitalis, diuretics and spironolactone, with no changes in medication in the previous 16 weeks. An echocardiogram showed a 17% left ventricular ejection fraction and the patient was in New York Heart Association Functional Class III. Before starting the exercise training programme, the patient was submitted to a maximal progressive cardiopulmonary exercise test, on an electromagnetically braked cycle ergometer (Medifit 400L; Medical Fitness Equipment, Maarn, The Netherlands), with work rate increments of 5 W every 1 min at 60 rpm until exhaustion. Oxygen uptake ( V′ O2) and carbon dioxide production were determined by means of gas exchange on a breath-by-breath basis in a computerised system (Vmax 229 model; SensorMedics, BuenaVista, CA, USA). Peak V′ O2 was defined as the maximum attained V′ O2 at the end of the exercise period in which the patient could no longer maintain the cycle rate. During this test, the patient showed a very low exercise capacity, with a peak V′ O …