901-71 Repeated Exercise Induced Ischemia Causes Myocardial Preconditioning

Abstract

Repeated short episodes of coronary occlusion in experimental animals cause myocardial preconditioning which reduces the extent of further ischemia. The purpose of the present study was to assess whether preconditioning also occurs during repeated exercise induced ischemia. Twenty-six coronary patients with positive exercise tests had 3 treadmill exercise tests at 30 minutes intervals. Two additional stress tests were performed on each of the previous 2 days, in order to eliminate/reduce the training effect. The 1st exercise test was regarded as baseline, while the 2nd (ex-2) and 3rd (ex-3) were compared to the 1st. Time to 1 mm ST depression (STD), recovery time (from maximal ischemia to 1 mm STD), total ischemic time (from 1 mm STD during exercise to regression of ischemia to 1 mm), double product at 1 mm STD and exercise duration were assessed. Exercise p 1 2 3 1 vs 2 1 vs 3 Time to 1mm (sec) 487 593 572 0004 0021 Recovery Time (sec) 259 126 109 00001 000002 Total Ischemic Time (sec) 633 399 430 00001 0002 Double Product at 1mm 20322 22325 21298 0008 0.163 Exercise Duration (sec) 862 864 885 0887 0.235 Preconditioning (defined as an improvement of 10% or more) was seen in 2 or more parameters in 76% of the patients. These data indicate that total ischemic time and recovery time were markedly reduced and that time to 1 mm STD was prolonged and the double product at 1 mm of STD (ischemic threshold) was higher in the second exercise. This is the first evidence that myocardial preconditioning occurs during repeated exercise induced ischemia.