Risk stratification following acute myocardial infarction

In industrialized countries the rate of sudden cardiac death remains unchanged. The most frequently encountered structural heart disease in these patients is coronary artery disease. Despite the era of thrombolytic therapy of acute myocardial infarction patients carry an increased risk of sudden cardiac arrhythmogenic death within a time period of one to two years following the acute event. Therefore, risk stratification post-MI before patient discharge is furthermore mandatory. The spectrum of non-invasive techniques for risk stratification includes the clinical risk profile, measurement of left ventricular global function (LV ejection fraction), the resting ECG (QT dispersion), an ECG stress test (detection and severity of myocardial ischemia), ambulatory ECG monitoring (number and type of ventricular arrhythmias), surface high resolution ECG (detection of ventricular late potentials), measurement of T wave alternans (TWA, alternans ratio), and measurements of the activity and balance of the autonomous nervous system (heart rate variability, baroreflex sensitivity = BRS). Programmed ventricular stimulation (PVS) serves as an invasive risk stratification technique (detection of an arrhythmogenic substrate). The prognostic power of the noninvasive techniques is limited; in general, the prognostic value of a negative test is reasonably high (90 to 100 % depending on the test used), whereas the prognostic value of a positive test is rather low (4 to 42 % depending on the test used). Combining several non-invasive tests may significantly improve the positive predictive value above 50 %, but this goes along with a significant decreases of sensitivity below 50 %. Therefore, a combination of several non-invasive tests (detection and exclusion of a large number of low-risk individuals) with the invasive method of PVS (detection of an arrhythmogenic substrate, i.e, a high-risk patient) seems reasonable, as has been convincingly shown by several smaller prognostic studies.