STUDIES ON THE ELECTRICAL SYSTOLE (“Q-T” INTERVAL) OF THE HEART

Abstract

In cardiac failure resulting from various causes [121 [male], 100 [female] patients] the electrical systole ("Q-T" interval of the electrocardiogram) has been found prolonged beyond normal limits [116 [male][male], 117 [female][female], taking into consideration the rate of the heart. This is expressed in K, which is the ratio, systole ("Q-T" interval) : square root of cycle length ("R-R" interval) . No direct relation between degree of heart failure and the value of K was found, but relative prolongation of the "Q-T" interval is present in the earliest recognizable cases of myocardial insufficiency. In rheumatic heart disease the value of K is not so high as in hypertensive and syphilitic cardiovascular disease. Elec-trocardiographic abnormalities such as prolonged conduction time and ventricular preponderance did not obviously affect the value of K nor was any correlation between value of K and size of heart seen. The factors that may be responsible for the relative prolongation of the "Q-T" interval in heart failure are discussed.