Low-density lipoprotein concentration in the normal left coronary artery tree

<p>Abstract</p> <p>Background</p> <p>The blood flow and transportation of molecules in the cardiovascular system plays a crucial role in the genesis and progression of atherosclerosis. This computational study elucidates the Low Density Lipoprotein (LDL) site concentration in the entire normal human 3D tree of the LCA.</p> <p>Methods</p> <p>A 3D geometry model of the normal human LCA tree is constructed. Angiographic data used for geometry construction correspond to end-diastole. The resulted model includes the LMCA, LAD, LCxA and their main branches. The numerical simulation couples the flow equations with the transport equation applying realistic boundary conditions at the wall.</p> <p>Results</p> <p>High concentration of LDL values appears at bifurcation opposite to the flow dividers in the proximal regions of the Left Coronary Artery (LCA) tree, where atherosclerosis frequently occurs. The area-averaged normalized luminal surface LDL concentrations over the entire LCA tree are, 1.0348, 1.054 and 1.23, for the low, median and high water infiltration velocities, respectively. For the high, median and low molecular diffusivities, the peak values of the normalized LDL luminal surface concentration at the LMCA bifurcation reach 1.065, 1.080 and 1.205, respectively. LCA tree walls are exposed to a cholesterolemic environment although the applied mass and flow conditions refer to normal human geometry and normal mass-flow conditions.</p> <p>Conclusion</p> <p>The relationship between WSS and luminal surface concentration of LDL indicates that LDL is elevated at locations where WSS is low. Concave sides of the LCA tree exhibit higher concentration of LDL than the convex sides. Decreased molecular diffusivity increases the LDL concentration. Increased water infiltration velocity increases the LDL concentration. The regional area of high luminal surface concentration is increased with increasing water infiltration velocity. Regions of high LDL luminal surface concentration do not necessarily co-locate to the sites of lowest WSS. The degree of elevation in luminal surface LDL concentration is mostly affected from the water infiltration velocity at the vessel wall. The paths of the velocities in proximity to the endothelium might be the most important factor for the elevated LDL concentration.</p

Is left coronary system more susceptible to atherosclerosis than right? A pathophysiological insight

On the basis of pathological, angiographical, intravascular ultrasound and computed tomography data coronary atherosclerosis appears to be more prevalent in the left coronary arterial system compared to the right. However, the pathophysiological mechanisms implicated in this discrepancy largely remain uncertain. The hemodynamic or anatomical differences between the right and left coronary artery might play a key role. Physiologically, the right coronary flow is more uniform during the cardiac cycle compared to the left, which experiences a remarkable systolic decline accompanied by a significant diastolic increment. Thus, the oscillatory shear stress, that constitutes a proved atherogenic factor, is more intense in regions with disturbed flow in the left coronary system. Likewise, the wall stress is more oscillatory during the cardiac cycle in the left coronary artery. On top of that, several differences regarding the anatomical configuration (3D geometry, branching) and the phasic motion between the right and the left arterial system appear to play a critical role in the modulation of the local atherogenic environment. Therefore, it could be assumed that the flow characteristics along with the geometrical and phasic motion patterns generate an intense oscillation of the imposed to the arterial wall stresses, especially in the left coronary artery. Over the long-term, these augmented oscillatory stresses, in combination with the effect of systemic risk factors, might modulate a more atherogenic environment in the atherosclerosis-prone regions of the left coronary system

Prevalence of ectasia in human coronary arteries in patients in northern Greece referred for coronary angiography

We determined the prevalence of coronary artery ectasia (CAE) in patients who were referred to our institution for coronary angiography for any reason and investigated its potential association with angiographically significant coronary artery disease (CAD). We also examined whether CAE and CAD are topographically associated. In 10,524 consecutive patients from January 1, 1995 to December 31, 2003, the corresponding coronary angiographies were analyzed and cases of CAE were identified, recorded, and summarized. CAE was found in 287 patients (2.7%). It was markedly more prevalent in men than in women (p < 0.0001). Younger patients exhibited a higher prevalence of CAE (p < 0.01), and this was confirmed for men (p < 0.05) but not for women. Co-existence with CAD was noted in 250 cases of CAE (87.1%) (p = 0.001). CAD increased remarkably throughout the study (p < 0.001), whereas the prevalence of CAE remained unchanged. The prevalence of CAE was significantly greater in the right coronary artery than in the left anterior descending (LAD) coronary artery and the left circumflex artery (p < 0.0001), whereas CAD most commonly affected the LAD (p < 0.0001). Further, CAE in the right coronary artery showed a strong association with the existence of CAD in the LAD (p = 0.015). In conclusion, CAE is more frequent in young men who show a predilection for the right coronary arterial system. Although associated with CAD, a direct causal relation cannot be established

Ventricular diverticulum: Definition, pathophysiology, clinical manifestations and treatment

Ventricular diverticula are rare abnormalities of the heart, whose origin is not fully understood yet. They are mostly congenital, either isolated or associated with other cardiac and extracardiac defects (Cantrell’s pentalogy). Although their etiology is not clear, an embryologic developmental defect has been proposed. Yet, some of them are associated with cardiomyopathies, inflammation or trauma. We discuss the case of a patient with hypertrophic cardiomyopathy and an apical diverticulum. The hypothesis made was that, an obstructing hypertrophic mass, localized in the midportion of the left ventricle, creates a pressure gradient between the apical and basal portions which finally leads to the creation of the diverticulum. Acute rupture, ventricular arrhythmias, peripheral arterial embolism and infective endocarditis are few of their complications. Besides transthoracic 2-D echocardiography and left ventriculography, magnetic resonance imaging (MRI) is the gold standard means of diagnosis. The opinions in the literature, as far as the pharmacological treatment or surgical resection, are controversial

Non-Newtonian models for molecular viscosity and wall shear stress in a 3D reconstructed human left coronary artery

The capabilities and limitations of various molecular viscosity models, in the left coronary arterial tree, were analyzed via: molecular viscosity, local and global non-Newtonian importance factors, wall shear stress (WSS) and wall shear stress gradient (WSSG). The vessel geometry was acquired using geometrically correct 3D intravascular ultrasound (3D IVUS). Seven non-Newtonian molecular viscosity models, plus the Newtonian one, were compared. The WSS distribution yielded a consistent LCA pattern for nearly all non-Newtonian models. High molecular viscosity, low WSS and low WSSG values occurred at the outer walls of the major bifurcation in proximal LCA regions. The Newtonian blood flow was found to be a good approximation at mid- and high-strain rates. The non-Newtonian Power Law, Generalized Power Law, Carreau and Casson and Modified Cross blood viscosity models gave comparable molecular viscosity, WSS and WSSG values. The Power Law and Walburn-Schneck models over-estimated the non-Newtonian global importance factor I(G) and under-estimated the area averaged WSS and WSSG values. The non-Newtonian Power Law and the Generalized Power Law blood viscosity models were found to approximate the molecular viscosity and WSS calculations in a more satisfactory way

Prevalence of narrowing >or=50% of the left main coronary artery among 17,300 patients having coronary angiography

We sought to investigate the prevalence of left main coronary artery significant stenosis (LMSS) (>or=50% of the luminal diameter) in an angiographic series of patients, to describe the associated coronary stenoses, and to assess the influence of age and gender on these findings. The angiograms of 17,323 consecutive patients from January 1, 1984 to December 31, 2003 were retrospectively analyzed. LMSS was found in 823 patients (4.8%) and was more predominant in men (p or=50% in the right coronary artery, the left circumflex artery, the left anterior descending artery, the intermediate artery, first and second obtuse marginal branch, posterior descending artery, and posterolateral branch was significantly more frequent in association with LMSS. Approximately half of the patients with LMSS also had triple-vessel disease. Co-existent disease in 3 major vessels with minor branches was more evident in men (men/women OR 1.77, 95% CI 1.08 to 2.88, p = 0.02). In contrast, LMSS without lesions in any of the other coronary arteries was found in [corrected] 4.7% of patients with LMSS, and this was more frequent in women (men/women OR 0.31, 95% CI 0.15 to 0.61, p = 0.001). In conclusion, men presented more frequently with LMSS and at a younger age than women. Also, LMSS with co-existent triple-vessel disease was more common in men

Sex-related differences in the angiographic results of 14,500 cases referred for suspected coronary artery disease

OBJECTIVE: To investigate sex differences of angiographic results in patients undergoing coronary angiography for suspected coronary artery disease (CAD). METHODS: We retrospectively assessed the coronary angiograms of 2840 women and 11,610 men from 1984 to 2003. We examined sex differences regarding the extent and topography of significant stenoses (SS) (i.e. > or =50% of the luminal diameter), the age of presentation, and the variation of the annual frequency of the angiographic findings across the study period. RESULTS: SS were recorded in 1817 women and 9984 men (64 vs. 86%, P<0.001). Women were more likely to present with nonsignificant stenoses (i.e. <50% of the luminal diameter) or angiographically normal coronaries (P<0.001). In patients with SS, women had a higher chance to present with one-vessel (P<0.001) or peripheral branches (P<0.05) disease, whereas men were more likely to have two-vessel disease (P<0.005). Compared with men, women were less likely to exhibit SS in the right coronary artery (P<0.001), left circumflex (P<0.01), intermediate artery (P<0.01) and first obtuse marginal branch (P<0.01). No significant sex differences were recorded in the frequency of SS in the left anterior descending artery. In patients aged from 31 to 60 years, SS were more common in men, whereas in patients 61-80 years of age SS were more common in women. The annual frequency of SS in women gradually increased throughout the study period. CONCLUSION: SS were less common in women, were found later in life, and were less likely to involve the right coronary artery, left circumflex, intermediate artery and first obtuse marginal branch than in men

Elevated heart rate and atherosclerosis: an overview of the pathogenetic mechanisms

Several epidemiological studies have reported that an elevated heart rate is associated with coronary atherosclerosis independently of other risk factors. In this review we explore the pathophysiologic mechanisms involved in the pro-atherosclerotic effect of elevated heart rate, apart from its association with sympathetic tone. An elevated heart rate enhances the magnitude and frequency of the tensile stress imposed on the arterial wall and prolongs the exposure of coronary endothelium to the systolic low and oscillatory shear stress. Moreover, increased heart rate intensifies the pulsatile motion of the heart and, therefore, the frequency of the periodically changing geometry of the coronary arteries, thereby affecting the local hemodynamic environment. All these processes induce structural and functional changes of the endothelial cells, which are accumulated over the time in atherosclerosis-prone regions promoting atherosclerosis. Heart rate should be considered in every patient with coronary heart disease, especially since it is an easily measurable and reproducible parameter. Slowing the heart rate could potentially decrease the progression of atherosclerosis by reducing the local pro-atherosclerotic vascular environment. This effect may be involved in any beneficial role of heart rate lowering agents in preventing coronary heart disease