Smart Damping Modulation of Carotid Wall Energetics in Human Hypertension: Effects of Angiotensin-Converting Enzyme Inhibition

Damping is the conversion of mechanical energy of a structure into thermal energy, and it is related to the material viscous behavior. To evaluate the role of damping in the common carotid artery (CCA) wall in human hypertension and the possible improvement of angiotensin-converting enzyme (ACE) inhibition, we used noninvasive CCA pressure (tonometry) and diameter (B-mode echography) waveforms in normotensive subjects (NT group; n=12) and in hypertensive patients (HT group; n=22) single-blind randomized into HT–placebo (n=10) or HT-treated (ramipril, 5 to 10 mg/d during 3 months; n=12). Vascular smooth muscle (VSM) null tonus condition was achieved from in vitro pressure and diameter waveforms (Konigsberg microtransducer and sonomicrometry) measured in explanted human CCA (n=14). Arterial wall dynamics was described by viscous (η), inertial (M), and compliance (C) parameters, mean circumferential wall stress, viscous energy dissipation (WD), peak strain energy (WSt), damping ratio (ξ=WD/WSt), and modeling isobaric indexes CIso and WSt(Iso). The lack of VSM tonus isobarically increased wall stress and reduced η, CIso, and damping (P