Vasoactive Drugs Influence Aortic Augmentation Index Independently of Pulse-Wave Velocity in Healthy Men

Abstract

Abstract-Aortic augmentation index, a measure of central systolic blood pressure augmentation arising mainly from pressure-wave reflection, increases with vascular aging. The augmentation index is influenced by aortic pulse-wave velocity (related to aortic stiffness) and by the site and extent of wave reflection. To clarify the relative influence of pulse-wave velocity and wave reflection on the augmentation index, we studied the association between augmentation index, pulse-wave velocity, and age and examined the effects of vasoactive drugs to determine whether altering vascular tone has differential effects on pulse-wave velocity and the augmentation index. We made simultaneous measurements of the augmentation index and carotid-to-femoral pulse-wave velocity in 50 asymptomatic men aged 19 to 74 years at baseline and, in a subset, during the administration of nitroglycerin, angiotensin II, and saline vehicle. The aortic augmentation index was obtained by radial tonometry (Sphygmocor device, PWV Medical) with the use of an inbuilt radial to aortic transfer function. In multiple regression analysis, the aortic augmentation index was independently correlated only with age (Rϭ0.58, PϽ0.0001). Nitroglycerin (3 to 300 g/min IV) reduced the aortic augmentation index from 4.8Ϯ2.3% to Ϫ11.9Ϯ5.3% (nϭ10, PϽ0.002). Angiotensin II (75 to 300 ng/min IV) increased the aortic augmentation index from 9.3Ϯ2.4% to 18.3Ϯ2.9% (nϭ12, PϽ0.001). These drugs had small effects on aortic pulse-wave velocity, producing mean changes from baseline of Ͻ1 m/s (each PϽ0.05). In healthy men, vasoactive drugs may change aortic augmentation index independently from aortic pulse-wave velocity. Key Words: antihypertensive agents Ⅲ aorta Ⅲ arteries Ⅲ hemodynamics Ⅲ pulse S ystolic blood pressure is augmented by the reflection of pressure from the periphery of the circulation to the aortic root. 1 The aortic augmentation index (AIx) is defined as the increment in pressure from the first systolic shoulder (inflection point) to the peak pressure of the aortic pressure waveform expressed as a percentage of the peak pressure. 2 This index has been used to measure the additional load imposed on the left ventricle as a result of wave reflection and correlates with left ventricular mass. 3,4 AIx depends, at least in part, on aortic and large-artery pulse-wave velocity (PWV). A higher PWV results in earlier arrival of reflected waves and, hence, increased augmentation during early systole. 1,5 PWV is inversely related to arterial distensibility. 6 Therefore, AIx has been proposed as an index of "arterial stiffness" 7,8 and has been used as a measure of this. 9 -12 However, in addition to PWV, AIx may depend on the pattern of ventricular ejection and on arterial properties determining the amount and site of wave reflection. 1 These latter factors may be influenced by the vascular tone of the small muscular arteries/arterioles rather than by the elastic properties of the aorta. To clarify the relationship between AIx and PWV, we made simultaneous measurement...

Interaction between pulse wave velocity, augmentation index, pulse pressure and left ventricular function in chronic heart failure

“…However, this positive correlation was not found after adjustment for age in a previous study. 36 Moreover, this relation implies that the coefficient and the sites of reflection are stable, which was probably not the case in our study because of the extensive arthrosclerosis and regional modifications of vascular resistance inherent in heart failure. 37 As previously reported, 21 we found regional heterogeneity of arterial stiffening according to EF status, probably partly because of the marked increase in proximal arterial stiffness associated with age.…”

Whole-body vibration training reduces arterial stiffness, blood pressure and sympathovagal balance in young overweight/obese women

“…38 Nitrate administration decreases SBP and AIx via a reduction in vascular tone of small arteries independently from aortic PWV. 39 In a previous study, we showed that acute WBV attenuated the increases in reflected wave magnitude, aSBP, leg PWV and baPWV during metaboreflex-induced sympathetic activation following a continuous 4 min session of static squat, suggesting that vibration-related factors induced functional sympatholysis in the legs. 22 In the current study, WBV training decreased the sympathovagal balance (LFnu/ HFnu) due to a concurrent decrease in sympathetic (LFnu) and increase in cardiovagal (HFnu) modulation.…”

Diastolic blood pressure is an important determinant of augmentation index and pulse wave velocity in young, healthy males

“…18,19 Other studies reported that augmentation index was correlated to both SBP and DBP 20 or only to SBP. 21,22 Interestingly, Cameron et al 21 found in a study population of 262 hypertensive subjects that augmentation index was correlated to DBP only in males and that this relation was lost when augmentation index was normalised for age.…”