Time-based risk assessment after myocardial infarction. Implications for timing of discharge and applications to medical decision-making.

Abstract

We evaluated timing of adverse cardiac events after thrombolysis to guide length of stay after ST-segment elevation myocardial infarction. Kaplan-Meier survival curves described timing of major postinfarction complications in 41021 fibrinolytic-treated patients in GUSTO-I. Using model-fitting, these data were best explained by a mixed-exponential survival model: an acute curve describing most adverse events and a chronic curve describing a lower background rate. We replicated this strategy in 15059 fibrinolytic-treated patients in GUSTO-III. From the relation between time and events described by the model's acute curve in GUSTO-III, we proposed times for hospital discharge. The acute curve explained 97% of deaths and 68%-96% of various event composites. Of complications within 10 days, 90% of deaths and 70% of acute curve death, stroke, shock, heart failure, or reinfarction occurred by 24 h. By 2.7 days, 95% of deaths, stroke, shock, heart failure, or reinfarction occurred. Most major ventricular arrhythmias occurred within 24 h, after which the hazard curve was flat. Mixed-exponential survival modelling describes timing of post-infarction complications and supports discharge 4 days after uncomplicated infarction. Such time-based risk assessment could guide decision-making in other settings in which randomized studies are impractical.