Arterial hemodynamics in human hypertension.

TLDR

Aortic impedance differences between normotensive and hypertensive individuals remain poorly defined. The study measured aortic impedance in 8 normotensive and 11 hypertensive Chinese patients during rest, nitroprusside, handgrip exercise, and before and after propranolol using cardiac catheterization. Hypertensive patients showed markedly higher resistance, characteristic impedance, external power, peripheral reflections, and impedance phase frequency, all of which were normalized by vasodilation; handgrip exercise did not worsen these abnormalities, while beta blockade further increased resistance and reflections, indicating that essential hypertension is driven by heightened vasomotor tone.

Abstract

Differences in aortic impedance between normotensives and hypertensives are not well characterized. We examined impedance in 8 normotensive and 11 hypertensive (mean 96.7 vs. 122.2 mmHg) age-matched, Chinese patients undergoing cardiac catheterization at rest, during nitroprusside, and handgrip exercise before and after beta blockade (propranolol). Hypertensives had higher resistance (2,295 vs. 1713 dyn-s/cm5), characteristic impedance (145.7 vs. 93.9 dyn-s/cm5), total external power (1,579 vs. 1174 mW), peripheral reflections (ratio of backward to forward wave components of 0.54 vs. 0.44), and first zero crossing of impedance phase angle (4.15 vs. 2.97 Hz). These abnormalities were eliminated with vasodilatation. Differences between groups were not further exacerbated when pressure was increased during handgrip exercise. Beta blockade further increased resistance and reflections. Thus, hemodynamic abnormalities of essential hypertension (increased resistance, reflections, and pulse wave velocity, and decreased compliance) are compatible with an increased vasomotor tone that is further unmasked during generalized beta blockade.