The diastolic duration as a percentage of the cardiac cycle in healthy adults: A pilot study.

Abstract

Background: A widely accepted concept in cardiovascular physiology states that diastole constitutes 62.5 % of the cardiac cycle during a typical 0.8-s cycle at 75 beats per minute. However, this has not been confirmed by using modern technology in healthy individuals.

Objective: This study aimed to accurately measure diastolic duration as a fraction of the cardiac cycle using echocardiography in healthy adults with structurally normal hearts.

Methods: In this prospective study, 200 healthy adults aged over 18 years, with heart rates between 50 and 100 beats per minute, normal ECGs, and structurally normal hearts, were included. Using a modified apical 5-chamber view and pulse wave Doppler at the aortic and mitral valves, researchers measured the RR interval (total cardiac cycle), diastolic duration (from aortic valve closure to mitral valve closure), and systolic duration. Three measurements were taken for each parameter, and the mean was used for analysis.

Results: Participants had a mean age of 47.7 years (range 19-79), with an equal gender distribution. The mean RR interval was 799 ± 97 ms. The left ventricular (LV) diastolic duration was 469 ± 76 ms, and the LV systolic duration was 330 ± 42 ms. The ratio of diastolic duration to the total cardiac cycle was 0.58 ± 0.04, slightly higher in males (0.59 ± 0.04) compared to females (0.57 ± 0.04).

Conclusion: This study challenges the longstanding teaching that diastole accounts for two-thirds of the cardiac cycle. Instead, diastole represents 58 % of the cycle, highlighting the need to reconsider its role in cardiovascular physiology and clinical applications.