New approaches to risk stratification after myocardial infarction

Parameters to assess the presence of electrical instability after myocardial infarction include spontaneous ventricular arrhythmias, late potentials, and programmed ventricular stimulation. The accuracy of the long-term electrocardiogram in correctly identifying high-risk patients has been questioned because spontaneous ventricular arrhythmias also occur in a large proportion of patients who do not develop ventricular tachycardia or sudden death during follow-up (false-positive results). In addition, many patients died suddenly without having these markers. Late potentials, although showing a good correlation to subsequent occurrence of sustained ventricular tachyarrhythmia or sudden death, are also burdened by the problem of a great number of false-positive results. Programmed ventricular stimulation (such as late potentials) assesses the presence of an arrhythmogenic substrate. An abnormal finding such as inducibility of ventricular tachyarrhythmia is predictive of subsequent occurrence of ventricular tachyarrhythmias. Combining these approaches, additionally including a low ejection fraction, subgroups of patients at very high risk of sudden death or sustained ventricular tachyarrhythmia can be identified. Noninvasive procedures (such as Holter monitoring or recording of late potentials) are desirable for screening purposes, whereas it would be acceptable to use more aggressive invasive techniques in certain subsets of patients. A step-like approach using noninvasive recording of late ventricular potentials as the initial step would allow the preselection of patients for further evaluation by invasive electrophysiological techniques.