Background: An estimated 50% of patients with myocardial infarction have prodromal unstable angina. There is controversy over whether prodromal unstable angina identifies a group of patients at lower risk of short- and long-term death and the clinical importance of recording this event.
Methods: Of 207 patients enrolled at a single Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-I) site, 196 survived the 24 hours after presentation, achieved peak creatine kinase MB concentrations, and were classified as having either abrupt symptom onset or prodromal unstable angina in the 2 weeks before myocardial infarction. Creatine kinase MB peak was used to categorize infarct size as aborted myocardial infarction, minor myocardial damage, or extensive myocardial injury. Follow-up was performed at 24 hours, 30 days, 1 year, and 5 years. Multiple variables, including prodromal unstable angina, time to treatment, age, sex, previous infarction and infarct location, were analyzed for predicting infarct size. Also, these variables plus peak creatine kinase MB level and a combined variable of prodromal unstable angina and peak creatine kinase MB level were examined for predicting survival.
Results: Mortality rate was 2.5% within 24 hours, 9.0% at 30 days, 13.5% at 1 year, and 27.1% at 5 years. Patients categorized as either aborted infarction or minor myocardial damage were significantly more likely to have prodromal unstable symptoms (81.3% vs 51.2%, P <.001) and better survival at each follow-up period. Prodromal presentation was the most significant predictor of infarct size category (P =.001). Five-year survival was predicted by age (P <.0001), peak creatine kinase MB level (P =.007), infarct location (P =.009), the combined variables (P =.029), and prodromal unstable angina (P =.017). Prodromal unstable angina had the highest odds ratio for 5-year survival at 3.83 (95% confidence interval 1.27-11.47).
Conclusions: Prodromal unstable angina is a strong predictor of infarct size and survival. Recognizing prodromal unstable angina is important for clinically assessing prognosis.