Prolongation of the QT interval and ventricular arrhythmias: Some early observations

Abstract

The QT interval has attracted the interest of clinicians and researchers since the very early years of electrocardiography. However, the reasons for this interest have changed significantly over the years. Because of the close correspondence between electrical systole (QT interval) and the mechanical cardiac systole, a fact that was noted by the discoverer of the human electrocardiogram (ECG) Augustus Waller, 1 the QT interval was regarded as a measure of the duration of mechanical systole and an index of cardiac pump function until approximately the 1950s. Prolongation of the QT interval relative to heart rate (the first observations of the relationship between the duration of the mechanical systole and heart rate were published in the middle of the 19th century, several decades before the discovery of the electrocardiogram) was known to occur in various acute and chronic cardiac diseases, electrolyte disturbances, cerebrovascular disorders, during treatment with quinidine, and in rare cases, without identifiable cause in the absence of any of the above conditions (reviewed in 1951 by Bellet 2 ). QT prolongation was considered by many investigators a useful diagnostic sign specifically in acute carditis of rheumatic and other origin. 3,4 The awareness of the link between QT prolongation and the risk of ventricular arrhythmias came much later, with the discovery of the congenital long QT syndrome 5‐7 and torsades de pointes (TdP), 8 but was preceded by clinical ob