MEASUREMENT OF THE QT INTERVAL AND THE RISK ASSOCIATED WITH QT(C) INTERVAL PROLONGATION - A REVIEW

The accurate measurement of the QT interval and its correction or adjustment for cycle length, age, and gender have been topics of increasing interest over the course of the past 70 years. The availability of digitized electrocardiographic recordings on large normal population together with statistical adjustment for pertinent covariates have provided useful data for defining QT interval prolongation. Data from the International Long QT Syndrome Registry Indicate that the probabilistic risk of developing malignant arrhythmias in patients with QT prolongation is exponentially related to the length of the QT(c) interval. The risk is further accentuated by the development of T-wave alternans, particularly at very prolonged QT(c) intervals.