REPEATED INTERMITTENT STRESS EXACERBATES MYOCARDIAL ISCHEMIA-REPERFUSION INJURY

Chronic stress in humans has been correlated with increased risk for i schemic heart disease. Thus experiments were conducted to determine if repeated intermittent restraint stress increased infarct size in a ra t model of myocardial ischemia-reperfusion injury. Male Sprague-Dawley rats were subjected to no stress (control) or to daily restraint stre ss for 1-1.5 h for 8-14 days (stress protocol A) or for 2 h daily for 11 or 12 days (stress protocol B). Myocardial ischemia-reperfusion (30 -min ischemia, 3-h reperfusion) was performed in anesthetized rats. Av erage baseline arterial pressures were 111 +/- 4, 120 +/- 10, and 125 +/- 7 mmHg in the control, stress protocol A, and stress protocol B gr oups, respectively. Infarct size (%area at risk) was significantly lar ger in both groups of stressed rats compared with control rats (58 +/- 5, 78 +/- 2, and 79 +/- 3% in the control, stress protocol A, and str ess protocol B groups, respectively). During ischemia or early reperfu sion, zero of eight control, two of six protocol A stress, and two of five protocol B stress rats had at least one period of severe arrhythm ia. Therefore, these results provide experimental evidence corroborati ng correlative studies in humans that link chronic stress with increas ed morbidity and mortality from ischemic heart disease.