The Q-II Interval

Abstract

A study of the second heart sound in 112 normal adults ranging in age from 21 to 50 years is presented, along with results, in 15 patients with advanced systemic hypertension. A detailed analysis of the Q-II_A and Q-II_P intervals, as related to heart rate, respiration, age, and blood pressure had been performed. A linear dependence on the √RR interval was noted in both groups. With advancing age, a statistically significant decrease in the Q-II_P was noted in the normal subjects. A decreased mobility of the Q-II_A and Q-II_P intervals with respiration was described. In hypertensive subjects, a significant prolongation of both the Q-II_A and Q-II_P intervals without variation in the II-_A-P interval (splitting) as compared to the normal subjects was found. The effect of respiration on the splitting of the second sound was also found to be comparable to the normal for the same age group. The relationship of changes in ventricular dynamics to systemic hypertension are discussed on the basis of these findings.