Determinants of elevated pulse pressure in middle-aged and older subjects with uncomplicated systolic hypertension -: The role of proximal aortic diameter and the aortic pressure-flow relationship

Background - Elevated pulse pressure ( PP) is associated with increased cardiovascular risk and is thought to be secondary to elastin fragmentation with secondary collagen deposition and stiffening of the aortic wall, leading to a dilated, noncompliant vasculature. Methods and Results - By use of calibrated tonometry and pulsed Doppler, arterial stiffness and pulsatile hemodynamics were assessed in 128 subjects with uncomplicated systolic hypertension ( supine systolic pressure greater than or equal to 140 mm Hg off medication) and 30 normotensive control subjects of comparable age and gender. Pulse-wave velocity was assessed from tonometry and body surface measurements. Characteristic impedance (Z(c)) was calculated from the ratio of change in carotid pressure and aortic flow in early systole. Effective aortic diameter was assessed by use of the water hammer equation. Hypertensives were heavier (P < 0.001) and had higher PP (P < 0.001), which was attributable primarily to higher Z(c) (P < 0.001), especially in women. Pulse-wave velocity was higher in hypertensives (P = 0.001); however, this difference was not significant after adjustment for differences in mean arterial pressure (MAP) (P > 0.153), whereas increased Z(c) remained highly significant (P < 0.001). Increased Z(c) in women and in hypertensive men was attributable to decreased effective aortic diameter, with no difference in wall stiffness at comparable MAP and body weight. Conclusions - Elevated PP in systolic hypertension was independent of MAP and was attributable primarily to elevated Z(c) and reduced effective diameter of the proximal aorta. These findings are not consistent with the hypothesis of secondary aortic degeneration, dilation, and wall stiffening but rather suggest that aortic function may play an active role in the pathophysiology of systolic hypertension.