Objectives: We evaluated the prognostic relevance of the extent of myocardial injury, as measured by a standard electrocardiographic (ECG) method, on the patients' long-term prognosis, its time dependence and its relation to fibrinolytic therapy efficacy.
Background: Many clinical and instrumental variables influence the short- and long-term prognoses of patients with acute myocardial infarction (MI). The extent of myocardial injury is relevant to predict both the short-term prognosis and the benefit of fibrinolytic treatment.
Methods: In 8,731 patients with MI enrolled in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto (GISSI-1) study, the number of ECG leads with ST-segment elevation was used to define the extent of myocardial injury and four different severity groups: A, B, C and D, with ST-segment elevation in two or three leads, four or five leads, six or seven leads and more than eight leads, respectively.
Results: At 10 years, the mortality rates were 36.6%, 41.0%, 47.9% and 51.2% in groups A, B, C and D, respectively. At 30 days, according to the extent of myocardial injury, the relative risk (RR) of death was significantly higher for groups B, C and D, compared with group A (RR 1.19 and 95% confidence interval [CI] 1.06 to 1.34 for group B; RR 1.54 and 95% CI 1.31 to 1.80 for group C; RR 2.01 and 95% CI 1.69 to 2.39 for group D). At one-year follow-up, the RR of death remained higher for groups C and D, whereas, subsequently, the extent of myocardial injury did not influence the RR of death. At 10 years, the differences in fibrinolytic treatment benefit between the four groups were similar to those at hospital discharge.
Conclusions: At 10 years, the survival rate appears to be related to the extent of myocardial injury, as evaluated by ST-segment elevation on the admission ECG.