The effect of percutaneous transluminal coronary angioplasty on anaerobic threshold in patients with angina pectoris.

The anaerobic threshold (AT) is regarded an objective parameter for evaluating exercise tolerance, but its relationship to the improvement of myocardial ischemia remains uncertain. To investigate this relationship, submaximal treadmill exercise tests were performed for 15 consecutive patients with angina pectoris who had undergone successful percutaneous transluminal coronary angioplasty (PTCA). Before and after PTCA, the AT was determined using cardiorespiratory monitoring, while the patients were receiving their usual vasodilator medications. 1) Before PTCA, the minute oxygen uptake (VO2) at the AT correlated well with the peak VO2 (r = 0.92, p < 0.002). The VO2 at the AT, however, showed less correlation (r = 0.71, p < 0.002) with the VO2 at ST segment depression, while the latter parameter correlated closely with the peak VO2 (r = 0.91, p < 0.002). 2) After PTCA, exercise time, peak VO2, and the double product at peak exercise increased significantly (from 640.1 +/- 212.2 to 772.9 +/- 230.0 sec, p < 0.001, from 19.1 +/- 5.2 to 22.4 +/- 4.9 ml/min/kg, p < 0.05, and from 19.7 +/- 5.0 x 10(3) to 23.7 +/- 4.5 x 10(3), p < 0.001, respectively). However, the VO2 at the AT did not increase significantly (from 15.8 +/- 4.1 to 16.6 +/- 3.5 ml/min/kg, p = NS). The heart rate, systolic blood pressure, and double product at the AT did not change significantly. In conclusion, in patients with angina pectoris, the AT is apparently related to the onset of myocardial ischemia. However, the AT does not necessarily reflect acute improvement of myocardial ischemia immediately after PTCA.