The Effect of Ischemic Preconditioning on Long-term Prognosis in Acute Myocardial Infarction

ABSTRACT

BACKGROUND AND OBJECTIVES: 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. SUBJECTS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.