Transesophageal Doppler echocardiography evaluation of coronary blood flow velocity in baseline conditions and during dipyridamole-induced coronary vasodilation.

SummaryBackground: The successful application of noninvasive Doppler spectrum analysis has been reported for the hemodynamic assessment of LIMA graft after myocardial revascularization.Hypothesis: The objective of this study was to assess the utility of transthoracic Doppler echocardiography (TTE) in providing information on LIMA flow in patients after coronary artery bypass graft surgery.Methods: In all, 22 patients (aged 62 ± 8 years) with LIMA graft to the left anterior descending (LAD) coronary artery who underwent coronary angiography were assessed using high-frequency (5 MHz) transthoracic Doppler echocardiography. They were compared with 25 patients with angina (control group A, aged 59 ± 12 years), in whom an ungrafted LIMA was assessed, and with 17 patients (control group B, aged 59 ± 9 years) with angiographically normal coronary arteries, in whom the LAD was assessed.Results: A biphasic pattern (systolic and diastolic) was recorded in all cases. In 14 patients with a normal graft or < 70% stenosis (Group 1) and in control group B, blood flow was maximal during diastole. In eight patients with severe graft stenosis > 70% (Group 2) and control group B, blood flow was maximal during systole, with low diastolic flow. The diastolic fraction of the velocity time integrals was 0.81 ± 0.11 for Group 1 and 0.25 ± 0.06 for Group 2 (p < 0.05). A diastolic velocity time integral fraction < 0.5 predicted > 70% stenosis

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“…This technique has been reported in the assessment of LAD stenoses using transesophageal echocardiography. 20 …”

Section: Discussionmentioning

confidence: 99%

Assessment of Left Internal Mammary Artery Graft Patency by Transthoracic Doppler Echocardiography

Elmasry

Salama

Darwish

et al. 2002

Clinical Cardiology

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“…The mean velocity is chosen to be 0.24 m s 21 as the average of the mean diastolic and systolic velocities in the LAD, so that the resulting mean Reynolds number (Re) based on the diameter of the artery is approximately 270 [33].…”

Section: Boundary Conditionsmentioning

confidence: 99%

Nitric oxide transport in an axisymmetric stenosis

Liu

Fan

et al. 2012

J. R. Soc. Interface.

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To test the hypothesis that disturbed flow can impede the transport of nitric oxide (NO) in the artery and hence induce atherogenesis, we used a lumen -wall model of an idealized arterial stenosis with NO produced at the blood vessel -wall interface to study the transport of NO in the stenosis. Blood flows in the lumen and through the arterial wall were simulated by Navier -Stokes equations and Darcy's Law, respectively. Meanwhile, the transport of NO in the lumen and the transport of NO within the arterial wall were modelled by advection -diffusion reaction equations. Coupling of fluid dynamics at the endothelium was achieved by the Kedem -Katchalsky equations. The results showed that both the hydraulic conductivity of the endothelium and the non-Newtonian viscous behaviour of blood had little effect on the distribution of NO. However, the blood flow rate, stenosis severity, red blood cells (RBCs), RBC-free layer and NO production rate at the blood vessel -wall interface could significantly affect the transport of NO. The theoretical study revealed that the transport of NO was significantly hindered in the disturbed flow region distal to the stenosis. The reduced NO concentration in the disturbed flow region might play an important role in the localized genesis and development of atherosclerosis.

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“…where U0 is the mean inlet velocity taken to be 24 cm/s as the average of the mean diastolic and systolic velocities in the LAD (11). To match the experimental conditions of Meyer et al (21), a constant pressure boundary condition of 70 mmHg is used at the outlet.…”

Section: Ajp-heart Circ Physiolmentioning

confidence: 99%

Computational modeling of coupled blood-wall mass transport of LDL: effects of local wall shear stress

Olgaç

Kurtcuoglu²,

Poulikakos³

2008

American Journal of Physiology-Heart and Circulatory Physiology

119

175

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Olgac U, Kurtcuoglu V, Poulikakos D. Computational modeling of coupled blood-wall mass transport of LDL: effects of local wall shear stress. Am J Physiol Heart Circ Physiol 294: H909-H919, 2008. First published December 14, 2007 doi:10.1152/ajpheart.01082.2007.-The work herein represents a novel approach for the modeling of lowdensity lipoprotein (LDL) transport from the artery lumen into the arterial wall, taking into account the effects of local wall shear stress (WSS) on the endothelial cell layer and its pathways of volume and solute flux. We have simulated LDL transport in an axisymmetric representation of a stenosed coronary artery, where the endothelium is represented by a three-pore model that takes into account the contributions of the vesicular pathway, normal junctions, and leaky junctions also employing the local WSS to yield the overall volume and solute flux. The fraction of leaky junctions is calculated as a function of the local WSS based on published experimental data and is used in conjunction with the pore theory to determine the transport properties of this pathway. We have found elevated levels of solute flux at low shear stress regions because of the presence of a larger number of leaky junctions compared with high shear stress regions. Accordingly, we were able to observe high LDL concentrations in the arterial wall in these low shear stress regions despite increased filtration velocity, indicating that the increase in filtration velocity is not sufficient for the convective removal of LDL.low-density lipoprotein transport; lipid accumulation; atherosclerosis; leaky junction MASS TRANSPORT of large molecules such as low-density lipoprotein (LDL) has received considerable interest in recent years because of its significance in the early stages of atherosclerosis. Locally elevated concentrations of LDL in the arterial wall are considered to be the initiator of atherosclerotic plaque formation (20,26). Various experimental (2,19,21,37,38) and computational (1, 13-15, 25, 31, 33, 40) studies have been conducted to comprehend the pathways and mechanisms governing LDL transport from the artery lumen into the arterial wall and within the arterial wall. There are two pathways of LDL transport through the endothelium: by vesicular transcytosis, which is regulated by receptors on the endothelial cells (30), and through leaky junctions, most of which are located at the sites of dying or replicating cells (18,19).Early experimental studies on LDL transport were performed in animals. The main method was systemic injection of LDL solution with subsequent harvesting and examination of the animal's arteries. Lin et al. (19) 2) used endothelial cell cultures to study LDL transport under pressurized conditions and found that LDL transport through leaky junctions constitutes the major part of total LDL transport (90.9%), whereas only a small portion occurs via the vesicular pathway (9.1%). Because the occurrence of leaky junctions is governed by the adjacent endothelial cells, and because the behavior o...

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Transesophageal Doppler echocardiography evaluation of coronary blood flow velocity in baseline conditions and during dipyridamole-induced coronary vasodilation.

Cited by 282 publications

References 19 publications

Assessment of Left Internal Mammary Artery Graft Patency by Transthoracic Doppler Echocardiography

Assessment of Left Internal Mammary Artery Graft Patency by Transthoracic Doppler Echocardiography

Nitric oxide transport in an axisymmetric stenosis

Computational modeling of coupled blood-wall mass transport of LDL: effects of local wall shear stress

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