Reproducibility of systolic and diastolic time intervals in normal humans: an important issue in clinical cardiovascular pharmacology.

The purpose of this study was to evaluate the long-term variability and reproducibility of systolic and diastolic time intervals in human subjects. Ten healthy volunteers underwent serial determinations of systolic and diastolic time intervals and, as internal physiologic standards, heart rate (HR), systemic blood pressures, and resting oxygen consumption (VO2). The protocol lasted 1 month and measurements were made on days 1, 2, and 30. No statistically significant differences were found in the various systolic time interval parameters, percentage of diastolic time, heart rate, systolic blood pressure (SBP) and resting oxygen consumption for the 3 study days. Diastolic blood pressure tended to rise slightly (p = 0.07) from day 1 to day 30. The average coefficients of variation for systolic and diastolic time interval parameters in individual study subjects ranged from 1.2 to 7.0%, whereas those for resting physiologic data ranged from 5.3 to 8.5%. In normal human subjects, systolic and diastolic time intervals are highly reproducible, with acceptable variation over time; these measurements should be thought of as possessing reproducibility equal to or greater than the resting physiologic parameters of HR, systemic blood pressure and oxygen consumption.