The brief repetitive periods of ischemia and reperfusion before a myocardial infarction appears to precondition the heart, making it more resistant to subsequent longer periods of ischemia. This phenomenon is known as ischemic preconditioning (IP). We studied the long-term effects of IP in patients with acute myocardial infarction.

Between January 1991 and August 1993, we examined, prospectively, 113 consecutive patients who had an acute myocardial infarction and arrived to the hospital within 6 hours after the onset of chest pain. IP was defined as prodromal angina within 24 hours before the myocardial infarction. Patients were divided 2 groups:Non-IP group and IP group. Clinical characteristics, laboratory findings, coronary angiographic findings, cardiac events, and mortality at admission and during follow-up were compared between these two groups.

The IP group had 64 patients while the Non-IP group had 49. In terms of risk factors for ischemic heart disease, hypertension was more common in the IP group (p<0.05). Peak serum creatine kinase level of the IP group was 1,387.0±1,255.0 IU/L and that of the Non-IP group was 2,372.7±2,420.5 IU/L (p<0.05). The time interval between the onset of infarction and peak creatine kinase level was shorter in the IP group than in the Non-IP group (10.6±4.8 hours vs. 7.1±4.6 hours;p<0.05). For cardiac events during the follow-up period, there were more incidences of congestive heart failure and reinfarction in the IP group than in the Non-IP group (p<0.05). Mortality rate did not differ between the two groups. Univariate analysis identified five factors predictive of 3-year mortality: age, sex, coronary angiogram frequency, hypertension, and smoking. However, none of these factors were independently associated with death in the multivariate analysis.

Close monitoring for cardiac events may be necessary for patients who have had IP before myocardial infarction as they had a higher incidence for congestive heart failure and reinfarction during the follow-up.