Preload, adrenergic activity, and aortic compliance in normal and hypertensive patients.
Aortic compliance is a major determinant of systolic blood pressure and of impedance to left ventricular ejection. However, little is known about its regulating factors. To assess the effects of preload and adrenergic activity on aortic compliance, we studied 10 normal subjects and nine untreated hypertensive patients at rest and during lower body negative pressure. Aortic compliance was measured invasively from the diastolic decay of the aortic pressure tracing and systemic vascular resistance. Preload was decreased stepwise by lower body negative pressure (-5 to -40 mm Hg) while adrenergic activity was assessed by the change in plasma norepinephrine at a maximum level of negative pressure suction. At rest, aortic compliance was lower in hypertensive subjects compared with its value in normal individuals (0.048 +/- 0.012 [SD] versus 0.071 +/- 0.009 units, p less than 0.001) but correlated inversely with systolic blood pressure in both groups (r = -0.64 in normotensive individuals, r = -0.83 in hypertensive subjects, r = -0.88 for the whole group, p less than 0.001 for all). Whereas resting pulmonary wedge pressure was higher in hypertensive subjects compared with normal individuals (16 +/- 4 [SD] versus 11 +/- 3 mm Hg, p less than 0.05), resting plasma norepinephrine levels were not different between the two groups (261 +/- 139 versus 251 +/- 103 pg/ml). Neither of these two resting indices correlated with baseline aortic compliance in both normotensive individuals and hypertensive patients. During lower body negative pressure (LBNP), cardiac filling pressure (right atrial pressure and pulmonary wedge pressure) as well as cardiac output decreased in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Madkour
M A
MA
Department of Heart and Hypertension, Cleveland Clinic Foundation, OH 44195-5069.
Levenson
J
J
Bravo
E L
EL
Simon
A
A
Fouad-Tarazi
F M
FM
D001011:Aorta / Q000503:physiopathology*; D006439:Hemodynamics; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000503:physiopathology*; D008150:Lower Body Negative Pressure; D009638:Norepinephrine / Q000097:blood; D012016:Reference Values; D012146:Rest; D013318:Stroke Volume; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013599:Systole
D009638:Norepinephrine