Short- and Long-Term Variation of Systolic and Diastolic Time Intervals at Rest and during Dynamic Exercise in Healthy Subjects

Abstract

The purpose of the study was to evaluate the within-day and between-day variation of systolic and diastolic time intervals at rest and during dynamic exercise. Eleven healthy subjects (aged 19-27 years) were included. Systolic and diastolic time intervals were recorded mechanocardiographically at rest and during bicycle ergometer exercise (heart rate 148-156 bpm) at 4 time points on 3 separate days with intervals of about 10 days (day 1, day 10 and day 20). Electromechanical systole (QS(2)I) was the most stable of all systolic time intervals, showing no statistically significant within-day or between-day variation. The intraindividual coefficient of variation (CV) for QS(2)I was 1.8% at rest and 2.2% during exercise. Left ventricular ejection time (LVETI) showed consistently higher values in the morning (p < 0.001), whereafter only minor fluctuations were seen. The CV for LVETI was 2.7% at rest and 2.8% during exercise. The preejection period (PEP) showed great fluctuations (p < 0.01); the CV was 12% at rest and 32% during exercise. Percentage of diastolic time showed a significant within-day variation (p < 0.05) during exercise only. The CV for percentage of diastolic time was 6.1% at rest and 8.5% during exercise. Of the time intervals, QS(2)I was especially stable both at rest and during dynamic exercise and remained so during a time span of 20 days.