Background: Reperfusion therapy for myocardial infarction, understood to reduce mortality by preserving left ventricular function, was initially expected to provide increasing benefits over time. Surprisingly, large controlled thrombolysis trials demonstrated maximum benefit at 4 to 6 weeks with no subsequent increased treatment advantage. Such studies, however, compared groups by assigned treatment, not physiological effectiveness.
Methods and results: We calculated 2-year survival differences among 2431 myocardial infarction patients according to early infarct artery patency and outcome left ventricular ejection fraction using Kaplan-Meier curves. Hazard ratios for significant survival determinants were derived from Cox regression models. Two-year vital status (minimum, 688 days) was determined in 2375 patients (97.7%). A substantial mortality advantage for early complete reperfusion (Thrombolysis in Myocardial Infarction [TIMI] grade 3) and for preserved ejection fraction occurred beyond 30 days. The unadjusted hazard ratio for the TIMI 3 group compared with lesser grades at 30 days was 0.57 (95% confidence interval [CI], 0.35 to 0.94) and 30 days to > or = 688 days was 0.39 (95% CI, 0.22 to 0.69). Consequently, early TIMI 3 flow was associated with approximately a 3 patient per 100 mortality reduction the first month with an additional 5 lives per 100 from 30 days to 2 years. For ejection fraction >40% compared with < or = 40%, the unadjusted hazard ratio was 0.25 (95% CI, 0.16 to 0.37) at 30 days and 0.22 (95% CI, 0.15 to 0.33) after 30 days through 2 years (lives saved, approximately 9 and 11 per 100, respectively).
Conclusions: Successful reperfusion and myocardial salvage produce significant mortality benefits that are amplified beyond the initial 30 days.