Pressure dependence of the canine aortic characteristic impedance and the effects of alterations in smooth muscle activity

Abstract

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Optimization of Hemodynamic Energy Expenditure in the Arterial System

“…1. Similar results were found by others with measurements made both in vitro and in vivo (5,27). In certain extrathoracic arteries (e.g., splenic artery) the characteristic impedance is a monotonously increasing function of pressure when smooth muscle is relaxed but exhibits the U-shape form after activation (21).…”

“…The aim of this presentation is to evaluate the experimental results from our and others' laboratories related to arterial wall biomechanics (1,5,13,(17)(18)(19)(20)(21)27) and circulatory wave dynamics (1 1,12,14,16,22,25, 29,30,32) in order to identify possible physiological control mechanisms optimizing the values of mean arterial pressure and the pulsatile pressure oscillations.…”

“…Adaptive physiological control mechanisms of both the peripheral resistance at precapillary level and the large artery impedance may be equally important in optiiizing the hemodynamic energy expenditure of the heart (10). The aim of this presentation is to evaluate the experimental results from our and others' laboratories related to arterial wall biomechanics (1,5,13,(17)(18)(19)(20)(21)27) and circulatory wave dynamics (1 1,12,14,16,22,25, 29,30,32) in order to identify possible physiological control mechanisms optimizing the values of mean arterial pressure and the pulsatile pressure oscillations.…”

Endografting of the Descending Thoracic Aorta Increases Ascending Aortic Input Impedance and Attenuates Pressure Transmission in Dogs

“…Endografting of the descending aorta in these dogs results in a 30% increase in the modulus of the AAII at frequencies below 5 Hz, a 65% increase in Z 0, and a 40% decrease in aortic compliance. An increase in Z 0 is usually attributed to an increase in local aortic stiffness, 17 suggesting that the stenting resulted in an increase in the modulus of elasticity of the ascending aorta. The increase in Z 0 following stent placement is similar in magnitude to that reported in patients following an aortic interposition graft of the descending thoracic aorta, 10 and less than the 90% increase in Z 0 seen following acute interposition grafting of the descending thoracic aorta in swine.…”

Non-invasive Determination of Aortic Mechanical Properties and Their Effects on Left Ventricular Function Following Endovascular Abdominal Aneurysm Repair

“…Our patients, unlike the animal studies, had endografts deployed more distally in the aorta (abdomen vs thoracic) which may be too remote to induce changes in the ascending aorta. Alternatively, inhaled volatile anesthetic's suppression of the sympathetic nervous system may have counteracted the proposed mechanism of sympathetic activation for the changes in local aortic mechanics following endograft implantation [37][38][39]. Our measured SVR was lower post-EVAR, likely reflecting the cumulative effect of general anesthesia on decreased sympathetic/vascular tone at the level of the small arteries and arterioles (considered to be the largest contributors to SVR) [40].…”