Changes in aortic stiffness and augmentation index after acute converting enzyme or vasopeptidase inhibition.
Augmentation index (AI), a measure of enhanced wave reflection, has been proposed as a bedside measure of aortic stiffness. However, because AI is potentially sensitive to various factors other than vessel wall stiffness, the utility of AI as a stiffness indicator may be limited. To assess relations between AI and vascular properties, we used arterial tonometry and aortic Doppler flow to evaluate trough (24 hours) and peak (4 hours) pulsatile hemodynamics and pulse wave velocity in 159 individuals with systolic hypertension at the completion of a 12-week period of monotherapy with the vasopeptidase inhibitor omapatrilat (80 mg; n=75) or the converting enzyme inhibitor enalapril (40 mg; n=84). Characteristic impedance (Zc) was calculated from the ratio of change in carotid pressure and aortic flow in early systole. Systolic ejection period (SEP), timing of wave reflection, and AI were assessed from the carotid waveform. Comparable acute reductions in mean pressure were associated with greater reductions in peripheral resistance with enalapril, whereas neither drug had an acute effect on Zc. Both drugs reduced AI, but neither drug altered the timing of wave reflection. Both drugs increased heart rate and shortened SEP. Multiple regression analysis demonstrated that the acute reduction in AI was most affected by reductions in SEP and peripheral resistance. Change in AI was inversely related to change in Zc and pulse wave velocity did not enter the model. Our findings indicate that AI is a complex surrogate marker that is inversely related to changes in proximal aortic stiffness in systolic hypertension.
Mitchell
Gary F
GF
Cardiovascular Engineering, Inc, Waltham, MA 02453, USA. GaryFMitchell@mindspring.com
Lacourcière
Yves
Y
Arnold
J Malcolm O
JM
Dunlap
Mark E
ME
Conlin
Paul R
PR
Izzo
Joseph L
JL
D000328:Adult; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use*; D001011:Aorta / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002339:Carotid Arteries / Q000503:physiopathology; D004311:Double-Blind Method; D004452:Echocardiography; D004548:Elasticity; D004562:Electrocardiography; D004656:Enalapril / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000503:physiopathology*; D008297:Male; D011480:Protease Inhibitors / Q000627:therapeutic use*; D011673:Pulsatile Flow; D011725:Pyridines / Q000627:therapeutic use*; D012044:Regression Analysis; D016037:Single-Blind Method; D013599:Systole; D013841:Thiazepines / Q000627:therapeutic use*
D000806:Angiotensin-Converting Enzyme Inhibitors; D011480:Protease Inhibitors; D011725:Pyridines; D013841:Thiazepines; C106266:omapatrilat; D004656:Enalapril