Abstract
Abnormal prolongation and shortening of the electrocardiographic QT interval duration, which occur in the hereditary forms of long and short QT syndromes, are associated with an increased risk of ventricular arrhythmias and sudden cardiac death. Even within the normal range, these altered durations are associated with an increased mortality risk in the general population. While extreme prolongation or reduction of the QT interval predisposes patients to malignant ventricular arrhythmias and sudden cardiac death, the precise dose-response relationship between the QT interval and cardiovascular disease mortality is still unknown. This paper describes the need for more standardized methods for measuring and reporting the QT interval and the need for more precise assessments of the risk associated with QT interval variation.