Ischemic preconditioning detected by treadmill exercise tests in patients with stable angina

The aim of this study was to explore the ischemic preconditioning (IP) phenomenon in patients with chronic stable angina (SA) by using treadmill exercise tests (TETs). Twenty-nine patients with SA were divided into 2 groups: group A (n = 15) and group B (n = 14). There was no difference between the 2 groups in both clinical characteristics and extent of coronary stenosis. Group A was subjected to 2 TETs at a 10-minute interval, but group B had a 60-minute interval according to Bruce protocol. The occurrence and time of chest pain, maximal value, duration of ST segment depression, and arrhythmias that occurred during TETs were analyzed for differences in the 2 tests in the 2 groups. In group A, 9 patients (60.0%) complained of chest pain in the first test, whereas only 4 (26.7%) did in the second test (p < 0.01); The time of occurrence of chest pain during exercise was 1.88 +/- 0.2 min in the first test, 2.3 +/- 0.4 min in the second test (p < 0.05); The maximal value of ST segment depression decreased from 0.21 +/- 0.09 mV in the first test to 0.14 +/- 0.05 mV in the second (p < 0.01); the duration of ST segment depression decreased from 7.12 +/- 0.9 min in the first test to 4.42 +/- 0.3 min in the second (p < 0.01). The incidence of arrhythmia decreased from 40.0% in the first test to 13.3% in the second (p < 0.05). However, no significant difference was observed in the multiple parameters, mentioned above, in group B. In conclusion, the first ischemic event could induce the IP phenomenon and protect the heart from more serious damage at a 10-minute interval. However, this effect disappeared when the second test was done at a 60-minute interval.