RISK STRATIFICATION AFTER MYOCARDIAL-INFARCTION - A REAPPRAISAL IN THE ERA OF THROMBOLYSIS

Objectives The present study was performed to evaluate whether the mod alities of risk stratification after myocardial infarction were still operative in the thrombolytic era. Background Prediction of fatal even ts 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 u pdated. Methods In this multicentre, prospective study, 471 acute myoc ardial infarction patients, 45% of whom were given thrombolytic therap y, were enrolled from the 10th day and underwent all or part of the fo llowing tests: exercise test, radionuclide ventriculography (resting a nd exertional ejection fraction), Holter monitoring, signal-averaged e lectrocardiography and programmed electrical stimulation. Univariate a nd multivariate analyses were performed to identify predictors of mort ality. Results One year and long-term (mean follow-up 31 . 4 months) m ortality rates were 5 . 5% and 8 . 4%, respectively. Prediction of mor tality was assessed and the role of the following variables was thus d etermined: age over 56 years (P=0 . 01), previous coronary attacks (P< 0 . 001), history of heart failure (P<0 . 001), early heart failure af ter myocardial infarction (P=0 . 017): maximum workload of lest than 1 20 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 . 0 12), mean night-time cycle length of less than 750 ms (P<0 . 001), sta ndard deviation of day time RR intervals of less than 100 ms (P=0 . 04 ), the last two measures reflecting heart rate variability. In this po pulation, neither ventricular ectopic activity nor inducibility of sus tained monomorphic ventricular tachycardia at electrophysiological stu dy carried any prognostic significance. Multivariate analyses showed t hat decreased heart rate variability, presence of late potentials and low ejection fraction (<30%) made an independent contribution to the s urvival models. Conclusion In the current context of management of acu te coronary patients, the basis for risk stratification after myocardi al infarction remain roughly unchanged.