Prediction of exercise tolerance in the chronic phase of myocardial infarction by using ventilatory gas analysis.
To predict exercise tolerance in the chronic phase of myocardial infarction (MI), cardiopulmonary exercise testing was performed using a ramp treadmill protocol in 25 patients at 1 and 3 months after the onset of MI. Oxygen uptake, heart rate and O2 pulse were estimated at rest, during a warm-up period, and at the levels of anaerobic threshold (AT), respiratory compensation (RC) and peak exercise. Results were as follows: 1) AT and peak oxygen uptake at 3 months after the onset of MI were 14.1 +/- 2.8 and 21.8 +/- 5.2 ml/min/Kg, respectively. 2) The subjects were divided into 2 groups according to peak oxygen uptake at 3 months: one showing peak oxygen uptake > 22 ml/min/Kg and the other < 22 ml/min/Kg. The former group (n = 13) was referred to as the good tolerance group, and the latter group (n = 12) was referred to as the poor tolerance group. Oxygen uptake at AT, RC and peak exercise was lower in the poor tolerance group than in the good tolerance group (11.2 vs 14.7, 15.1 vs 20.4, 17.1 vs 23.4 ml/min/Kg, respectively). 3) The increases in oxygen uptake from AT to RC and from AT to peak exercise were less in the poor tolerance group than in the good tolerance group. 4) O2 pulse at rest, warm-up, AT, RC and peak exercise were also lower in the poor tolerance group.2+ tolerance in the chronic phase of MI.