ACE Inhibition and Vascular Remodeling of Resistance Vessels: Vascular Compliance and Cardiovascular Implications

The arterial circulation is composed of conduit arteries that store blood in systole (capacitive function), small branch points that contribute to pressure oscillations and reflected waves (oscillatory function), and arterioles that control blood flow (resistance function). These vessels are lined by endothelial cells that secrete nitric oxide and other substances that influence smooth-muscle tone, growth, and structural remodeling. The role of endothelial function is greater in thin-walled vessels than in conduit arteries, including proximal elastic vessels with thick walls. Thus, endothelial dysfunction is most likely to raise resistance and alter pressure oscillations than to produce early changes in the conduit artery wall. Later structural changes, facilitated by endothelial dysfunction, lead to reduced large artery compliance and widened pulse pressure as markers of risk for a cardiovascular event. Angiotensin-converting enzyme inhibitors, particularly those with vascular effects, tend to restore endothelial function and may result in regression of the structural alterations. Pulse contour analysis is the most sensitive means of assessing both capacitive oscillatory and resistance vessel function of the vasculature. Noninvasive radial artery tonometry with computer analysis of diastolic pressure decay provides independent measures of capacitive function, oscillatory function, and resistance, which allows screening and monitoring of arterial function. Such monitoring should lead to more individualized management that could supplement pressure monitoring as a guide to the efficacy of therapeutic intervention.