Prediction of sudden cardiac death: appraisal of the studies and methods assessing the risk of sudden arrhythmic death.

Abstract

Since the recognition of the high incidence of cardiac arrest as the mechanism of sudden cardiac death (SCD), medical scientists and clinicians have sought methods to predict and prevent these events. Significant progress has already been made in the prediction and prevention of life-threatening arrhythmias during the last decade. This progress is highlighted by the outcomes of 4 recently published randomized studies demonstrating that the implantable cardioverter defibrillator (ICD) provides a mortality benefit compared with conventional drug therapy in highly specific subsets of patients.1–4 In parallel with intervention studies, several observational studies and reports have raised an optimistic notion that arrhythmic death can be predicted by methods potentially useful for widespread screening programs.5–10 Despite the evidence-based data and practical recommendations for indications of ICD therapy,11 utilization of this therapy has not been uniformly implemented worldwide, and screening of patients at potential high risk for arrhythmic death has not become a routine clinical practice. In addition to economic and educational factors, this may be due to methodological problems in the designs of a number of the completed observational and randomized intervention studies that confound the interpretation of the results and general application of the procedures. In this report, we analyze the problems of predicting arrhythmic deaths and the advantages and limitations of the various methods and studies, and we evaluate the need for new and better studies and methods of risk stratification. Three types of clinical research designs have been used to estimate the efficacy of interventions and the accuracy of methods for predicting sudden arrhythmic death: (1) observational follow-up studies, (2) case-control studies, and (3) randomized intervention designs. Observational studies are based on baseline assessment of 1 or more risk variables and subsequent follow-up of predefined patient groups. These studies have been most commonly used in the …