Effect of varying pulse interval in atrial fibrillation on left ventricular function in man.

The effect of spontaneous variation in RR interval due to atrialfibrillation on ventricular ejection was studied in I9 patients with aortic Starr-Edwards prostheses. Reduction in the interval be- tween the onset of ventricular activation and the opening sound of the prosthesis (QAi) is due to an increase in the initialforce acting on the ball. Negative correlation was present in all patients between QAi interval and the RR interval immediately preceding, which was associated with progressive reduction in the gradient across the prosthesis during diastole. Positive correlation was present in I4 out of I9 patients between the second preceding RR interval and QAI interval, which was not due to changes in ventricular filling or end-diastolic pressure gradient across the prosthesis, and appeared to reflect a direct positive inotropic effect of RR interval. In 5 patients, all with evidence of heart failure, this effect was not shown. Thesefindings have been expressed in terms of multiple regression equations, and related to the clinicalfeatures of atrialfibrillation.