Alterations in Aortic Wave Reflection With Vasodilation and Vasoconstriction in Anaesthetized Dogs

• Published in: Canadian journal of cardiology Vol. 29; no. 2; pp. 243 - 253
• Main Authors: Wang, Jiun-Jr, PhD, Bouwmeester, J. Christopher, MSc, Belenkie, Israel, MD, Shrive, Nigel G., PhD, Tyberg, John V., MD, PhD
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01-02-2013
• Subjects: Anesthesia, General; Animals; Aorta, Thoracic - drug effects; Aorta, Thoracic - physiopathology; Arterial Pressure; Cardiovascular; Disease Models, Animal; Dogs; Hypertension - diagnosis; Hypertension - physiopathology; Methoxamine - pharmacology; Nitroprusside - pharmacology; Vasoconstriction - drug effects; Vasoconstriction - physiology; Vasoconstrictor Agents - pharmacology; Vasodilation - drug effects; Vasodilation - physiology; Vasodilator Agents - pharmacology
• ISSN: 0828-282X; 1916-7075
• DOI: 10.1016/j.cjca.2012.03.001

Abstract Background Using the reservoir-wave approach, we studied wave propagation, reflection, and re-reflection in the canine aorta with administrations of sodium nitroprusside (NP) and methoxamine (Mtx). Methods In 8 anaesthetized dogs, excess pressures were calculated from pressure and flow measurements at 4 locations along the aorta; wave intensity analysis was employed to identify wavefronts and the type of waves. Results NP (intravenous; 14 μg/min) decreased mean aortic pressure from 80 ± 3 mm Hg to 48 ± 1 mm Hg; Mtx (intravenous; 10 μg/min) increased mean pressure from 80 ± 3 mm Hg to 104 ± 4 mm Hg. NP increased negative reflection near the kidneys (reflection coefficient: −0.33 vs −0.18; P < 0.01) and produced new negatively reflecting sites just beyond the arch and in the proximal femoral arteries, consistent with a vasodilating effects of nitrates on conducting arteries. Mtx negated negative reflection from near the kidneys (−0.02 vs −0.17; P < 0.01) and increased positive femoral reflection (0.38 vs 0.26; P < 0.01). The large reflected compression wave was re-reflected from the closed aortic valve to produce a prominent increase in middiastolic pressure in the distal aorta. Conclusions The reservoir-wave approach explains decreasing diastolic pressure without positing waves that travel at near-infinite velocities and reveals the pressure changes that are uniquely due to wave motion.