Does ischemic preconditioning occur during rehabilitation of ischemic patients?

Ischemic preconditioning is generally a short duration phenomenon, but during acute myocardial infarction a better inhospital outcome of patients with previous angina suggests that the effect of ischemic preconditioning could be longer than it was considered until now. It was also demonstrated that during successive exercise stress testings (ET) ST depression became lesser as a consequence of ischemic preconditioning. We investigated the possible occurrence of ischemic preconditioning during rehabilitation of ischemic patients. There were studied 43p with old myocardial infarction or stable effort angina, 29 men and 14 women, aged 33-68 years, divided in two groups: group I (19p) was included in a cardiac rehabilitation programme (15-20 sessions) and group II (24p) was not. All the patients were submitted to two ET at a month interval, for group I before and after cardiac rehabilitation programme. The peak-effort level was significantly greater for group I (80.26 +/- 7.2w vs 93.42 +/- 8.3w p < 0.05) but not for group II (65.5 +/- 5.8w vs 72.91 +/- 6.5w p > 0.05) during the two ET. The double product (21.573 +/- 3122 vs 24.168 +/- 3423 for group I and 23.551 +/- 3100 vs 21.000 +/- 2752 for group II) was not significantly different (p > 0.05) during the two ET. The same unsignificant modification was noted for maximal ST depression for group II (1.458 +/- 0.32 vs 1.166 +/- 0.21 mm p > 0.05) but not for group I patients in which maximal ST depression during the second ET was significantly less than during the first ET (1.52 +/- 0.23 vs 0.736 +/- 0.12 mm p < 0.05). Because cardiac rehabilitation does not influence the ischemic threshold and because the lesser maximal ST depression during the second ET was noted at the same, or even greater, double product (MVO2), we consider that it can be attributed to ischemic preconditioning.