[The relation between the anaerobic threshold and exercise-induced myocardial ischemia in patients with ischemic heart disease].

The aim of this study was to clarify whether the anaerobic threshold (AT) in patients with ischemic heart disease is determined by exercise-induced myocardial ischemia. A) The reproducibility of the VO2 at the AT (AT VO2) were studied. In 13 patients with exercise-induced myocardial ischemia, submaximal Treadmill exercise tests were performed twice using a cardiopulmonary monitoring system. The reproducibility of the AT VO2 was good (r = 0.92), and the mean +/- SD was -1.3 +/- 8.2%. B) The change of the AT VO2 after percutaneous transluminal coronary angioplasty (PTCA) was studied. In 30 patients who underwent successful PTCA, submaximal Treadmill exercise tests were performed before and after PTCA using a cardiopulmonary monitoring system. After PTCA both the exercise duration and the peak VO2 increased significantly (569.0 +/- 200.8 sec vs 681.9 +/- 206.9 sec, p < 0.001: 19.5 +/- 3. 4ml/min/kg vs 21.3 +/- 3.7ml/min/kg, p < 0.001). On the other hand, the AT VO2 did not increase (13.7 +/- 3.0 ml/min/kg vs 13.9 +/- 3.2ml/min/kg, NS). The significant increase of the AT VO2, more than 15.1%, was recognized only in 5 patients. Neither did the AT VO2 increase even in patients without hibernating myocardium. In conclusion, there are many cases in which AT is not determined by exercise-induced myocardial ischemia.