High variability in the reproducibility of key hemodynamic responses to head-up tilt.

Increased blood pressure upon standing is considered a cardiovascular risk factor. We investigated the reproducibility of changes in aortic blood pressure, heart rate, stroke volume, cardiac output, and systemic vascular resistance during three passive head-up tilts (HUT) in 223 participants without cardiovascular medications (mean age 46 years, BMI 28 kg/m2, 54% male). Median time gap between the first and the second HUT was 9 weeks and the second and the third HUT 4 weeks.

Individual changes of central blood pressure in response to upright posture: different hemodynamic phenotypes.

Objectives: Most studies about upright regulation of blood pressure have focused on orthostatic hypotension despite the diverse hemodynamic changes induced by orthostatic challenge. We investigated the effect of passive head-up tilt on aortic blood pressure.

Methods: Noninvasive peripheral and central hemodynamics in 613 volunteers without cardiovascular morbidities or medications were examined using pulse wave analysis, whole-body impedance cardiography and heart rate variability analysis.