Duration of ST segment depression after exercise-induced myocardial ischemia is influenced by body position during recovery but not by type of exercise

Abstract

To assess whether the duration of ischemic ST segment depression after exercise can be modified by changes in body position during recovery or with different types of exercise, 18 patients with chronic stable angina, positive exercise test results, and documented coronary artery disease were prospectively studied. Every patient underwent testing with three different exercise protocols: (1) Bruce (Bruce-standing recovery), (2) abrupt onset of exercise (abrupt), and (3) modified Bruce protocol preceded by a 10-minute warm-up period (warm-up). After exercise test patients recovered in a sitting position. In addition, all patients performed a fourth exercise (Bruce protocol), but this time they recovered in the supine position (Bruce-supine recovery). Time and heart rate-blood pressure product at 1 mm ST segment depression were similar for Bruce-standing recovery, abrupt, and Bruce-supine recovery protocols (5.1 ± 2, 4.4 ± 2, and 5.2 ± 2 minutes and 20.8 ± 4, 21.3 ± 4, and 20.4 ± 4 beats/min × mm Hg × 10 −3, respectively. Heart rate and heart rate-blood pressure product at peak exercise did not differ in Bruce-standing recovery, abrupt, and Bruce-supine recovery. Maximal ST segment depression was −2.0, −1.9, and −2.0 mm with Bruce-standing recovery, abrupt, and Bruce-supine recovery exercise, respectively, and −1.5 mm with warm-up exercise ( p < 0.05). Duration of ST segment depression into recovery was significantly prolonged after Bruce-supine recovery exercise (9.4 + 5 minutes) compared with Bruce-standing recovery, abrupt, and warm-up protocols (6.8 + 3, 5.9 + 4, and 5.0 + 3 minutes, respectively; p < 0.05). Thus in patients with chronic stable angina the duration of recovery from ischemia after exercise can be influenced by body position but not by type of exercise or magnitude of ST depression achieved during exercise.