In healthy volunteers, preejection period increased during head-up tilt and decreased during mental arithmetic, demonstrating that its use as a sympathetic activity index is confounded by changes in preload and afterload.
Observational (n=49)
No
Does preejection period (PEP) accurately reflect sympathetic activity during mental and orthostatic stress in healthy humans?
Preejection period is influenced by confounding factors like preload and afterload, and should be measured simultaneously with other cardiovascular variables to properly interpret sympathetic activity.
p-value: p=<0.0001
In previous studies, one of the systolic time intervals - preejection period (PEP) - was used as an index of sympathetic activity reflecting the cardiac contractility. However, PEP could be also influenced by several other cardiovascular variables including preload, afterload and diastolic blood pressure (DBP). The aim of this study was to assess the behavior of the PEP together with other potentially confounding cardiovascular system characteristics in healthy humans during mental and orthostatic stress (head-up tilt test - HUT). Forty-nine healthy volunteers (28 females, 21 males, mean age 18.6 years (SD=1.8 years)) participated in the study. We recorded finger arterial blood pressure by volume-clamp method (Finometer Pro, FMS, Netherlands), PEP, thoracic fluid content (TFC) - a measure of preload, and cardiac output (CO) by impedance cardiography (CardioScreen® 2000, Medis, Germany). Systemic vascular resistance (SVR) - a measure of afterload - was calculated as a ratio of mean arterial pressure and CO. We observed that during HUT, an expected decrease in TFC was accompanied by an increase of PEP, an increase of SVR and no significant change in DBP. During mental stress, we observed a decrease of PEP and an increase of TFC, SVR and DBP. Correlating a change in assessed measures (delta values) between mental stress and previous supine rest, we found that deltaPEP correlated negatively with deltaCO and positively with deltaSVR. In orthostasis, no significant correlation between deltaPEP and deltaDBP, deltaTFC, deltaCO, deltaMBP or deltaSVR was found. We conclude that despite an expected increase of sympathetic activity during both challenges, PEP behaved differently indicating an effect of other confounding factors. To interpret PEP values properly, we recommend simultaneously to measure other variables influencing this cardiovascular measure.
Krohová et al. (Fri,) conducted a observational in Healthy (n=49). Head-up tilt (HUT) and mental arithmetic task (MA) vs. Supine rest and recovery was evaluated on Change in preejection period (PEP) during HUT and MA (p=<0.0001). In healthy volunteers, preejection period increased during head-up tilt and decreased during mental arithmetic, demonstrating that its use as a sympathetic activity index is confounded by changes in preload and afterload.