Difference in the topography of atherosclerosis in the left versus right coronary artery in patients referred for coronary angiography.

BACKGROUND: We sought to determine the difference in the localization of coronary artery disease (CAD) between the left and right coronary artery system and investigate the effect of sex and age on that difference. METHODS: We retrospectively analyzed 17,323 consecutive angiographies from January 1st, 1984 to December 31st, 2003. The demographic parameters, in particular age and sex of the investigated cases as well as the angiographic results were recorded and summarized. RESULTS: Of 13,305 cases with CAD, 861 (6.5%) had right coronary artery (RCA)-only disease, 4,621 (34.7%) had left coronary artery (LCA)-only disease, while 7,823 (58.8%) cases had concomitant RCA and LCA disease. LCA-only disease was more frequent than RCA-only disease [LCA-only/RCA-only odds ratio (OR): 5.37, 95% CI: 4.99 to 5.77, p < 0.001]. Women were more likely to have LCA-only disease (men/women OR 0.75 95% CI: 0.68 to 0.82, p < 0.001) compared with men who were more likely to present with concomitant RCA and LCA disease (men/women OR 1.33 95% CI: 1.21 to 1.45, p < 0.001). RCA-only and LCA-only disease were both more frequent in patients aged from 51 to 60 years, while concomitant RCA and LCA disease in patients between 61 and 70 years of age. CONCLUSIONS: LCA-only disease is more frequent than RCA-only disease. Men have a higher probability than women to present with concomitant RCA and LCA disease while women are more likely than men to be found with LCA-only disease.

Prevalence, clinical correlates and treatment of permanent atrial fibrillation among the elderly: insights from the first prospective population-based study in rural Greece.

To investigate the prevalence of permanent atrial fibrillation (AF), its clinical associated conditions and treatment status in the elderly population in rural Greece. 720 people (46.1% males) older than 65 years (mean age: 72.5 +/- 5.7 years) living in four villages in rural Greece were screened with an electrocardiogram (response rate: 90.5%) for the presence of permanent AF. They underwent a physical examination, including blood pressure (BP) measurement, and body mass index (BMI) calculation, in addition to an interview about their medical history, physical activity, smoking habits, alcohol consumption and medication use. Subjects with AF for whom anticoagulants were contraindicated were identified and stroke risk stratification was performed using the CHADS2 algorithm. The prevalence of permanent AF was 5% (6.6% among men and 3.6% among women) and it increased with age. In the entire population, ECG evidence of myocardial ischaemia and ventricular premature beats were independently associated with the presence of permanent AF (OR 5.266; 95% CI 2.22-12.49, P = 0.0001 and OR 2.61; 95% CI 1.059-6.432, P = 0.037, respectively), while female sex was independently associated with the absence of the AF (OR 0.327; CI 0.147-0.729, P = 0.006). From those patients who were eligible for anticoagulation, 40.6% were treated with anticoagulants, 34.3% were given antiplatelets therapy and the rest received no antithrombotic treatment. This is the first prospective study demonstrating the prevalence, clinical correlates and treatment status of permanent AF in Greece. These results confirm the high prevalence of permanent AF among the elderly and underscore the issue regarding anticoagulants underutilization.

Impaired right ventricular systolic function demonstrated by reduced atrioventricular plane displacement in adults with Marfan syndrome.

AIMS: The right ventricle (RV) ejects the same volume of blood at the same rate as the left ventricle (LV). Mild LV dysfunction has been demonstrated in Marfan syndrome (MFS). However, little attention has been paid to the functioning of the RV. The aim of this study was to assess RV function in unoperated adult MFS patients. METHODS AND RESULTS: In 66 unoperated (15-58 years) MFS patients and 61 controls, rate of pressure rise (dp/dt) in RV, and tricuspid annular motion (TAM) were studied using conventional echocardiography and tissue Doppler imaging (TDI). When compared with controls, MFS patients showed impaired RV systolic function as expressed by a reduced dp/dt, TAM obtained by M-mode echocardiography, and peak TDI systolic velocities at the basal lateral wall (745.36+/-37.85 vs. 1103.30+/-27.30 mmHg, P<0.001; 2.2+/-0.05 vs. 2.5+/-0.05 cm, P<0.001; and 0.13+/-0.002 vs. 0.16+/-0.002 m/s, P<0.001, respectively). CONCLUSION: This study demonstrated a primary impairment of RV systolic function in MFS. This is the first study to report RV dysfunction in MFS. Such data could prove valuable during the peri-operative and long-term medical management of MFS patients.

In vivo comparative study of linear versus geometrically correct three-dimensional reconstruction of coronary arteries.

Although conventional linear 3-dimensional (3D) reconstruction of coronary arteries by intravascular ultrasound has been widely used for the assessment of plaque volume and progression; the volumetric error (VE) that is produced has not been adequately studied. Linear and geometrically correct 3D reconstruction was applied in 16 coronary arterial segments from 9 patients. Using geometrically correct reconstruction as reference, VE was assessed in 1-mm-long arterial slices. Although for the entire length of the coronary arteries VEs for lumen, external elastic membrane (EEM), and intima-media volumes were minimal (lumen VE 0.4%, -0.8 to 1.8; EEM VE 0.3%, -0.9 to 1.9; intima-media VE 0.4%, -1.4 to 2.2), the VE in each arterial slice exhibited a large variation from -15.6% to 36.2% for lumen volume, from -12.9% to 33.1% for EEM volume, and from -17.2% to 46.7% for intima-media volume, suggesting that linear reconstruction over- or underestimates the true arterial volumes. Lumen VE, EEM VE, and intima-media VE were also significantly higher in curved arterial subsegments than in relatively straight arterial subsegments (p <0.05). In conclusion, in highly curved arterial subsegments, the VE that is produced by linearly stacking the intravascular ultrasound images may be not negligible. Geometrically correct reconstruction of coronary arteries provides more reliable arterial reconstructions and plaque volume measurements. It is anticipated that clinical application of this technique will contribute to more accurate follow-up of the progression of atherosclerosis and assessment of arterial remodeling.

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.

Low-Density Lipoprotein concentration in the normal Left Coronary Artery tree.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Gender-specific differences in hypertension prevalence, treatment, control, and associated conditions among the elderly: data from a Greek population.

PURPOSE: In the present study we sought to assess the gender-specific prevalence, treatment rates, and control of hypertension, as well as to identify its associated conditions and additional cardiovascular (CV) risk factors, in a Greek population aged > or = 65 years old. METHODS: This is a population-based study including a clinical interview, an ECG recording, and blood pressure (BP) measurements by sphygmomanometer. RESULTS: The overall prevalence of hypertension was 83.3%, higher in females and increasing with age. In males, hypertension was independently associated with increased body mass index (BMI), a history of stroke, and myocardial infarction, while in females increased age, BMI, and a history of diabetes were independently associated with hypertension. A considerable proportion of hypertensives were treated (77.3%), while an effective control of BP was achieved in 42.5% of treated subjects. Despite the fact that hypertension treatment rates did not differ between the genders, control rates were lower among females. Finally, more hypertensive females presented additional CV risk factors than normotensives. CONCLUSION: Elderly females exhibit a higher prevalence of hypertension and are characterized by lower hypertension control compared to hypertensive males.

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.

Trimetazidine administration minimizes myocardial damage and improves left ventricular function after percutaneous coronary intervention.

BACKGROUND AND OBJECTIVE: The aim of this study was to evaluate whether the administration of trimetazidine, a piperazine derivative, to patients before and after percutaneous coronary intervention (PCI) minimizes the PCI-induced myocardial damage and improves left ventricular function 1 and 3 months after the procedure. METHODS: Fifty-two patients hospitalized for acute coronary syndromes (ACS) were included in this study. Patients were randomized into two groups: group A (trimetazidine group; n = 27) and group B (placebo group; n = 25). All patients received conventional antianginal therapy. In addition, group A patients received oral trimetazidine 20 mg every 8 hours, starting 15 days before PCI and continuing for 3 months after the procedure. For each patient, serum troponin I and creatinine kinase (CK)-MB levels were measured before PCI, then at 6, 24, and 48 hours after the procedure; a 2D cardiac echocardiogram was performed before PCI and at 1 and 3 months after the procedure. RESULTS: Twenty-four hours after PCI, troponin I levels were >1 ng/mL in 7 of 27 patients (26%) of group A and 11 of 25 patients (44%) in group B. Fourty-eight hours after revascularization troponin levels remained elevated in 15% of patients in group A and in 32% of patients in group B. Twenty-two percent of patients in group A had CK-MB levels >5 ng/mL, 24 hours after PCI, compared with 40% of patients in group B; four patients of group A had high CK-MB levels prior to PCI procedure. Echocardiographic measurements before revascularization revealed that 11 of 27 patients (40%) in group A had an ejection fraction <50% versus 8 of 24 patients (33%) in group B . The number of patients with an ejection fraction <50% was significantly reduced in group A compared with group B at 1 and 3 months after PCI, i.e. 11% versus 16% (p = 0.046) at 1 month and 4% versus 16% (p = 0.017) at 3 months.A significant improvement in regional wall motion was noted after treatment with trimetazidine compared with placebo. One month after PCI, inferior left ventricular (LV) wall hypokinesia had improved in 4 of 6 trimetazidine recipients and in 4 of 14 placebo recipients (p = 0.014, group A vs group B). After 3 months inferior wall hypokinesia improved in four patients in group A versus six patients in group (p = 0.05). Similarly, anterior LV wall motion improved in 3 of 11 patients in group A and in 1 of 6 patients in group B at 1 month. After 3 months anterior wall hypokinesia had improved in eight patients in group A and in two patients in group B (p = 0.04, group A vs group B). CONCLUSION: The metabolic agent trimetazidine appears to minimize myocardial reperfusion injury during PCI and improves global and regional wall motion at 1 and 3 months after PCI. This study was limited by small patient numbers and further studies are necessary to evaluate exact mechanisms of action and clinical implications of using trimetazidine in conjunction with PCI.

Flow parameters in normal left coronary artery tree. Implication to atherogenesis.

The dominant haemodynamic flow parameters of wall pressure (WP), wall shear stress (WSS), molecular viscosity and the spatial gradients: wall pressure gradient (WPG) and wall shear stress gradient (WSSG) along the normal human left coronary artery (LCA) tree are numerically analyzed in relation to atheronegenesis. The LCA tree includes the left main coronary artery, the left anterior descending branch, the left circumflex branch and their major branches. Spatial differentiation indicates that low values of WP (locally), WPG, WSS, WSSG and high molecular viscosity appear opposite flow dividers and this probably correlates to atherosclerosis localization.

A novel active contour model for fully automated segmentation of intravascular ultrasound images: in vivo validation in human coronary arteries.

The detection of lumen and media-adventitia borders in intravascular ultrasound (IVUS) images constitutes a necessary step for the quantitative assessment of atherosclerotic lesions. To date, most of the segmentation methods reported are either manual, or semi-automated, requiring user interaction at some extent, which increases the analysis time and detection errors. In this work, a fully automated approach for lumen and media-adventitia border detection is presented based on an active contour model, the initialization of which is performed via an analysis mechanism that takes advantage of the inherent morphologic characteristics of IVUS images. The in vivo validation of the proposed model in human coronary arteries revealed that it is a feasible approach, enabling accurate and rapid segmentation of multiple IVUS images.

Conceptual Foundations of Systems Biology Explaining Complex Cardiac Diseases.

Systems biology is an important concept that connects molecular biology and genomics with computing science, mathematics and engineering. An endeavor is made in this paper to associate basic conceptual ideas of systems biology with clinical medicine. Complex cardiac diseases are clinical phenotypes generated by integration of genetic, molecular and environmental factors. Basic concepts of systems biology like network construction, modular thinking, biological constraints (downward biological direction) and emergence (upward biological direction) could be applied to clinical medicine. Especially, in the field of cardiology, these concepts can be used to explain complex clinical cardiac phenotypes like chronic heart failure and coronary artery disease. Cardiac diseases are biological complex entities which like other biological phenomena can be explained by a systems biology approach. The above powerful biological tools of systems biology can explain robustness growth and stability during disease process from modulation to phenotype. The purpose of the present review paper is to implement systems biology strategy and incorporate some conceptual issues raised by this approach into the clinical field of complex cardiac diseases. Cardiac disease process and progression can be addressed by the holistic realistic approach of systems biology in order to define in better terms earlier diagnosis and more effective therapy.

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.

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 <0.001). Men with LMSS (median age 63 years, interquartile range 57 to 69) were younger than the women (median age 67 years, interquartile range 61 to 72, p <0.001). Logistic regression analyses revealed male gender (odds ratio [OR] 1.79, 95% confidence interval [CI] 1.46 to 2.18, p <0.001) and age (OR 1.05, 95% CI 1.04 to 1.06, p <0.001) as independent predictors of LMSS. In the total series, luminal narrowing >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.

Parathyroid hormone-related protein is reduced in severe chronic heart failure.

In the cardiovascular system, parathyroid hormone-related peptide (PTHrP) is expressed in various cells such as cardiac vascular smooth muscle cells, coronary endothelial cells and cardiomyocytes and acts as an autocrine/paracrine substance. We compared PTHrP levels in 35 consecutive patients with severe CHF (33 male, mean age 66.2 +/- 8.9 years) with 26 normal controls (24 male, mean age 63.1 +/- 8.6 years). PTHrP levels were reduced in severe CHF patients (11.10 +/- 1.37 fmol/ml) compared with the controls (20.62 +/- 3.30 fmol/ml, p = 0.005). PTHrP values decreased as a function of New York Heart Association classification. These results suggest that PTHrP levels decrease in proportion to the severity of heart failure and could potentially be used to monitor progression of disease non-invasively.

In-vivo validation of spatially correct three-dimensional reconstruction of human coronary arteries by integrating intravascular ultrasound and biplane angiography.

OBJECTIVES: The in-vivo validation of geometrically correct three-dimensional reconstruction of human coronary arteries by integrating intravascular ultrasound and biplane coronary angiography has not been adequately investigated. The purpose of this study was to describe the reconstruction method and investigate its in-vivo feasibility and accuracy. METHODS: In 17 coronary arteries (mean length, 85.7+/-17.1 mm) from nine patients, an intravascular ultrasound procedure along with a biplane coronary angiography was performed. From each angiographic projection, a single end-diastolic frame was selected in order to reconstruct the intravascular ultrasound catheter trajectory in space. In each end-diastolic intravascular ultrasound image, the lumen and media-adventitia contours were detected semi-automatically by an active contour algorithm. Each pair of contours was located on the catheter trajectory appropriately and interpolated with the adjacent pairs creating a three-dimensional volume of the arterial lumen and wall. The reconstructed lumen was back-projected onto both angiographic planes and the agreement between the back-projected and the angiographic luminal outlines was calculated. RESULTS: The angiogram-derived catheter length showed very high correlation (y=0.97 x + 1.8, P<0.001) and agreement with the corresponding pullback-derived values. Accordingly, the semi-automated segmentation of intravascular ultrasound images was also in significant correlation (r> or =0.96, P<0.001) and agreement with the reference manual tracing. The back-projected luminal borders showed good overall association with the corresponding angiographic ones (r=0.78, P<0.001) as well as remarkable agreement. CONCLUSIONS: Spatially correct three-dimensional reconstruction of human coronary arteries constitutes an imaging method with considerably high in-vivo feasibility and accuracy.

In-vivo accuracy of geometrically correct three-dimensional reconstruction of human coronary arteries: is it influenced by certain parameters?

OBJECTIVE: The geometrically correct three-dimensional reconstruction of human coronary arteries by integrating intravascular ultrasound (IVUS) and biplane angiography constitutes a promising imaging method for coronaries with broad clinical potential. The determinants of the accuracy of the method, however, have not been investigated before. METHODS: In total, 17 arterial segments (right coronary artery, n=7; left anterior descending, n=4; left circumflex, n=6) derived from nine patients were three-dimensionally reconstructed by applying three-dimensional intravascular ultrasound. The degree of matching between the reconstructed lumen back-projected onto each angiographic plane and the actual lumen in each plane was used as a measure of method's accuracy. The investigated factors that could potentially affect the reliability of the method included the type of the artery (left anterior descending, left circumflex, right coronary artery) and several geometrical and morphological characteristics of the reconstructed arteries. RESULTS: The correlation between the back-projected reconstructed lumens and the actual angiographic ones was found to be high (r=0.78, P<0.001). Neither the category of the reconstructed arteries nor their particular geometrical and morphological characteristics influenced the accuracy of the reconstruction method significantly. Nonetheless, the method exhibited slightly less accuracy in the reconstruction of right coronary arteries, an observation that could be attributed to the more intense pulsatile motion that this artery experiences during the cardiac cycle compared to the left anterior descending and left circumflex artery. CONCLUSIONS: The in-vivo accuracy of three-dimensional intravascular ultrasound (3D IVUS) is significantly high regardless of the type of the coronary arteries or their particular geometrical and morphological characteristics. This finding further supports the applicability of the method for either diagnostic or investigational purposes.

Spatial and phasic oscillation of non-Newtonian wall shear stress in human left coronary artery bifurcation: an insight to atherogenesis.

OBJECTIVE: To investigate the wall shear stress oscillation in a normal human left coronary artery bifurcation computational model by applying non-Newtonian blood properties and phasic flow. METHODS: The three-dimensional geometry of the investigated model included the left main coronary artery along with its two main branches, namely the left anterior descending and the left circumflex artery. For the computational analyses a pulsatile non-Newtonian flow was applied. To evaluate the cyclic variations in wall shear stress, six characteristic time-points of the cardiac cycle were selected. The non-Newtonian wall shear stress variation was compared with the Newtonian one. RESULTS: The wall shear stress varied remarkably in time and space. The flow divider region encountered higher wall shear stress values than the lateral walls throughout the entire cardiac cycle. The wall shear stress exhibited remarkably lower and oscillatory values in systole as compared with that in diastole in the entire bifurcation region, especially in the lateral walls. Although the Newtonian wall shear stress experienced consistently lower values throughout the entire cardiac cycle than the non-Newtonian wall shear stress, the general pattern of lower wall shear stress values at the lateral walls, particularly during systole, was evident regardless of the blood properties. CONCLUSIONS: The lateral walls of the bifurcation, where low and oscillating wall shear stress is observed, are more susceptible to atherosclerosis. The systolic period, rather than the diastolic one, favors the development and progression of atherosclerosis. The blood viscosity properties do not seem to qualitatively affect the spatial and temporal distribution of the wall shear stress.

Wall shear stress in normal left coronary artery tree.

Despite the fact that the role of wall shear stress (WSS) as a local mechanical factor in atherogenesis is well established, its distribution over the entire normal human left coronary artery (LCA) tree has not yet been studied. A three-dimensional computer generated model of the epicardial LCA tree, based on averaged human data set extracted from angiographies, was adopted for finite-element analysis of the Navier-Stokes flow equations treating blood as non-Newtonian fluid. The LCA tree includes the left main coronary artery (LMCA), the left anterior descending (LAD), the left circumflex artery (LCxA) and their major branches. In proximal LCA tree regions where atherosclerosis frequently occurs, low WSS appears. Low WSS regions occur at bifurcations in regions opposite the flow dividers, which are anatomic sites predisposed for atherosclerotic development. On the LMCA bifurcation, at regions opposite to the flow divider, dominant low WSS values occur ranging from 0.75 to 2.25 N/m2. High WSS values are encountered at all flow dividers. This work determines, probably for the first time, the topography of the WSS in the entire normal human LCA epicardial tree. It is also the first work determining the spatial WSS differentiation between proximal and distal normal human LCA parts. The haemodynamic analysis of the entire epicardial LCA tree further verifies the implications of the WSS in atherosclerosis mechanisms.

Molecular viscosity in the normal left coronary arterial tree. Is it related to atherosclerosis?

The purpose of this study is to elucidate, probably for the first time, the distribution of molecular viscosity in the entire left coronary artery (LCA) tree. The governing mass, momentum, and energy flow equations were solved by using a previously validated 3-dimensional numerical (finite-element analysis) code. High-molecular-viscosity regions occur at bifurcations in regions opposite the flow dividers, which are anatomic sites predisposed for atherosclerotic development. Furthermore, high-molecular-viscosity values appear in the proximal regions of the LCA tree, where atherosclerosis frequently occurs. The effect of blood flow resistance, due to increased blood viscosity, gives rise to increased contact time between the atherogenic particles of the blood and the endothelium, probably promoting atherosclerosis. Observations suggest that, whole viscosity distribution within the coronary artery tree may represent a risk factor for the resulting atherosclerosis. This distribution can become a possible tool for the location of atherosclerotic lesions.