Factors presaging early recurrent myocardial infarction ("extension").

A prospective study of 200 consecutive patients with acute myocardial infarction was undertaken to characterize the frequency and severity of early recurrent infarction (extension), manifested by secondary plasma MB creatine kinase (CK) and myoglobin peaks, and to identify patients at particularly high risk. Serial MB CK and myoglobin determinations and continuous electrocardiographic recordings were obtained in all patients for 14 days, and serial radioventriculograms were obtained in selected patients. Chest pain and S-T segment changes occurred often, in 57 and 43 percent, respectively, of the entire group of patients. However, a secondary rise in plasma MB CK levels indicative of recurrent infarction, occurring an average of 10 +/- 4 days after the initial infarct, was evident in only 17 percent of patients. Forty-three percent (25 of 58) of patients with initial subendocardial infarction exhibited recurrent infarction compared with only 8 percent of those with initial transmural infarction. The mortality rate was 7 percent in patients with subendocardial infarction without early recurrence compared with 16 percent among those with recurrent. Logistic regression analysis indicated that obese women with initial subendocardial infarction and repeated episodes of prolonged chest pain had a high probability rate (60 percent) of recurrence in contrast to the low probability (2 percent) in patients without these features. Thus, early recurrent infarction is frequent after subendocardial infarction and is associated with a marked increase in mortality. These results suggest that patients with subendocardial infarction are at particularly high risk for recurrent infarction and that patients with this type of infarction require vigorous monitoring and prolonged surveillance.