Risk stratification after myocardial infarction

Objectives The present study was performed to evaluate whether the modalities of risk stratification after myocardial infarction were still operative in the thrombolytic era. Background Prediction of fatal events in the aftermath of myocardial infarction relies on tests which aim to assess myocardial function, residual ischaemia and propensity for ventricular arrhythmias. Recent data on improved myocardial infarction prognosis have led to the view that risk stratification needs to be updated. Methods In this multicentre, prospective study, 471 acute myocardial infarction patients, 45% of whom were given thrombolytic therapy, were enrolled from the 10th day and underwent all or part of the following tests: exercise test, radionuclide ventriculography (resting and exertional ejection fraction), Holter monitoring, signal-averaged electrocardiography and programmed electrical stimulation. Univariate and multivariate analyses were performed to identify predictors of mortality. Results One year and long-term (mean follow-up 31·4 months) mortality rates were 5·5% and 8·4% respectively. Prediction of mortality was assessed and the role of the following variables was thus determined: age over 56 years ( P =0·01), previous coronary attacks ( P >0·001), history of heart failure ( P >0·001), early heart failure after myocardial infarction ( P =0·017), maximum workload of lest than 120 W at exercise test ( P =0·014), ineligibility to perform exercise ( P =0·002), depressed left ventricular ejection fraction ( P =0·013), late potentials as identified using 50 Hz high pass filtering ( P =0·012), mean night-time cycle length of less than 750 ms ( P 0·001), standard deviation of day time RR intervals of less than 100 ms ( P =0·04), the last two measures reflecting heart rate variability. In this population, neither ventricular ectopic activity nor inducibility of sustained monomorphic ventricular tachycardia at electrophysiological study carried any prognostic significance. Multivariate analyses showed that decreased heart rate variability, presence of late potentials and low ejection fraction (>30%) made an independent contribution to the survival models. Conclusion In the current context of management of acute coronary patients, the basis for risk stratification after myocardial infarction remain roughly unchanged.