Effect of variation in coronary artery anatomy on distribution of stenotic lesions

Design of experiment approach to identify the dominant geometrical feature of left coronary artery influencing atherosclerosis

Background and Objective. Coronary artery geometry heavily influences local hemodynamics, potentially leading to atherosclerosis. Consequently, the unique geometrical configuration of an individual by birth can be associated with future risk of atherosclerosis. Although current researches focus on exploring the relationship between local hemodynamics and coronary artery geometry, this study aims to identify the order of influence of the geometrical features through systematic experiments, which can reveal the dominant geometrical feature for future risk assessment.Methods. According to Taguchi's method of design of experiment (DoE), the left main stem (LMS) length (lLMS), curvature (kLMS), diameter (dLMS) and the bifurcation angle between left anterior descending (LAD) and left circumflex (LCx) artery (αLAD-LCx) of two reconstructed patient-specific left coronary arteries (LCA) were varied in three levels to create L9 orthogonal array. Computational fluid dynamic (CFD) simulations with physiological boundary conditions were performed on the resulting eighteen LCA models. Average helicity intensity (h2) and relative atheroprone area (RAA) of near-wall hemodynamic descriptors were analyzed.Results. The proximal LAD (LADproximal) was identified to be the most atheroprone region of the left coronary artery due to higherh2,large RAA of time averaged wall shear stress (TAWSS < 0.4 Pa), oscillatory shear index (OSI ∼ 0.5) and relative residence time (RRT > 4.17 Pa-1). In both patient-specific cases, based onh2and TAWSS,dlmsis the dominant geometric parameter while based on OSI and RRT,αLAD-LCxis the dominant one influencing hemodynamic condition in proximal LAD (p< 0.05). Based on RRT, the rank of the geometrical factors is:αLAD-LCx>dLMS>lLMS>kLMS, indicating thatαLAD-LCxis the most dominant geometrical factor affecting hemodynamics at proximal LAD which may influence atherosclerosis.Conclusion. The proposed identification of the rank of geometrical features of LCA and the dominant feature may assist clinicians in predicting the possibility of atherosclerosis, of an individual, long before it will occur. This study can further be translated to be used to rank the influence of several arterial geometrical features at different arterial locations to explore detailed relationships between the arterial geometrical features and local hemodynamics.

Left main coronary artery morphological phenotypes and its hemodynamic properties

BACKGROUND

Atherosclerosis may be linked to morphological defects that lead to variances in coronary artery hemodynamics. Few objective strategies exit at present for generalizing morphological phenotypes of coronary arteries in terms of hemodynamics. We used unsupervised clustering (UC) to classify the morphology of the left main coronary artery (LM) and looked at how hemodynamic distribution differed between phenotypes.

METHODS

In this study, 76 LMs were obtained from 76 patients. After LMs were reconstructed with coronary computed tomography angiography, centerlines were used to extract the geometric characteristics. Unsupervised clustering was carried out using these characteristics to identify distinct morphological phenotypes of LMs. The time-averaged wall shear stress (TAWSS) for each phenotype was investigated by means of computational fluid dynamics (CFD) analysis of the left coronary artery.

RESULTS

We identified four clusters (i.e., four phenotypes): Cluster 1 had a shorter stem and thinner branches (n = 26); Cluster 2 had a larger bifurcation angle (n = 10); Cluster 3 had an ostium at an angulation to the coronary sinus and a more curved stem, and thick branches (n = 10); and Cluster 4 had an ostium at an angulation to the coronary sinus and a flatter stem (n = 14). TAWSS features varied widely across phenotypes. Nodes with low TAWSS (L-TAWSS) were typically found around the branching points of the left anterior descending artery (LAD), particularly in Cluster 2.

CONCLUSION

Our findings demonstrated that UC is a powerful technique for morphologically classifying LMs. Different LM phenotypes exhibited distinct hemodynamic characteristics in certain regions. This morphological clustering method could aid in identifying people at high risk for developing coronary atherosclerosis, hence facilitating early intervention.

Relationship between Coronary Arterial Geometry and the Presence and Extend of Atherosclerotic Plaque Burden: A Review Discussing Methodology and Findings in the Era of Cardiac Computed Tomography Angiography

Coronary artery disease (CAD) represents a modern pandemic associated with significant morbidity and mortality. The multi-faceted pathogenesis of this entity has long been investigated, highlighting the contribution of systemic factors such as hyperlipidemia and hypertension. Nevertheless, recent research has drawn attention to the importance of geometrical features of coronary vasculature on the complexity and vulnerability of coronary atherosclerosis. Various parameters have been investigated so far, including vessel-length, coronary artery volume index, cross-sectional area, curvature, and tortuosity, using primarily invasive coronary angiography (ICA) and recently non-invasive cardiac computed tomography angiography (CCTA). It is clear that there is correlation between geometrical parameters and both the haemodynamic alterations augmenting the atherosclerosis-prone environment and the extent of plaque burden. The purpose of this review is to discuss the currently available literature regarding this issue and propose a potential non-invasive imaging biomarker, the geometric risk score, which could be of importance to allow the early detection of individuals at increased risk of developing CAD.

Bench testing and coronary artery bifurcations: a consensus document from the European Bifurcation Club

This is a consensus document from the European Bifurcation Club concerning bench testing in coronary artery bifurcations. It is intended to provide guidelines for bench assessment of stents and other strategies in coronary bifurcation treatment where the United States Food and Drug Administration (FDA) or International Organization for Standardization (ISO) guidelines are limited or absent. These recommendations provide guidelines rather than a step-by-step manual. We provide data on the anatomy of bifurcations and elastic response of coronary arteries to aid model construction. We discuss testing apparatus, bench testing endpoints and bifurcation nomenclature.

Use of factor analysis to characterize arterial geometry and predict hemodynamic risk: application to the human carotid bifurcation

The detailed geometry of atherosclerosis-prone vascular segments may influence their susceptibility by mediating local hemodynamics. An appreciation of the role of specific geometric variables is complicated by the considerable correlation among the many parameters that can be used to describe arterial shape and size. Factor analysis is a useful tool for identifying the essential features of such an inter-related data set, as well as for predicting hemodynamic risk in terms of these features and for interpreting the role of specific geometric variables. Here, factor analysis is applied to a set of 14 geometric variables obtained from magnetic resonance images of 50 human carotid bifurcations. Two factors alone were capable of predicting 12 hemodynamic metrics related to shear and near-wall residence time with adjusted squared Pearson's correlation coefficient as high as 0.54 and P-values less than 0.0001. One factor measures cross-sectional expansion at the bifurcation; the other measures the colinearity of the common and internal carotid artery axes at the bifurcation. The factors explain the apparent lack of an effect of branch angle on hemodynamic risk. The relative risk among the 50 bifurcations, based on time-average wall shear stress, could be predicted with a sensitivity and specificity as high as 0.84. The predictability of the hemodynamic metrics and relative risk is only modestly sensitive to assumptions about flow rates and flow partitions in the bifurcation.

Percutaneous coronary intervention and the no-reflow phenomenon

No-reflow during percutaneous coronary intervention (PCI) is observed most commonly during saphenous vein graft intervention, rotational atherectomy and primary PCI for acute ST-elevation myocardial infarction. The contributions of distal embolization and ischemia/reperfusion injury to the pathogenesis of no-reflow vary in these settings, as does prevention and management. Prevention of no-reflow in these high-risk groups is the best treatment strategy, employing antiplatelet agents, vasodilators and/or mechanical devices to prevent distal embolization. Once mechanical factors are excluded as a cause for reduced epicardial flow, the treatment of established no-reflow is mainly pharmacologic, since the obstruction occurs at the level of the microvasculature. Compared with patients in whom no-reflow is transient, refractory no-reflow is associated with a markedly increased risk of 30-day mortality.

Risk assessment of slow or no-reflow phenomenon in aortocoronary vein graft percutaneous intervention

Slow or no-reflow phenomenon (SNR) complicates 10%-15% of cases of percutaneous intervention (PCI) in aortocoronary saphenous vein grafts (SVG). At present, there are no uniform, effective strategies to predict or prevent this common and potentially serious complication. The purpose of our study was to characterize variables correlated with the risk of SNR in SVG PCI in the era of stenting and glycoprotein IIb/IIIa receptor inhibitors. We identified 2,898 consecutive patients who had PCI, of whom 163 underwent PCI of at least one SVG. The clinical and angiographic characteristics of patients who developed SNR (SNR group) were compared with those who did not (no-SNR group). A total of 23 patients experienced SNR and 140 did not. Using a stepwise multivariate logistic regression analysis, four independent predictors for SNR were detected: probable thrombus (OR 6.9; 95% CI, 2.1-23.9; P = 0.001), acute coronary syndromes (OR 6.4; 95% CI, 2.0-25.3; P = 0.003), degenerated vein graft (OR 5.2; 95% CI, 1.7-16.6; P = 0.003), and ulcer (OR 3.4; 95% CI, 0.99-11.6; P = 0.04). The risk of developing SNR could be estimated according to the number of predictors found: low-grade risk (1%-10%) if < or = one variable was present, moderate risk (20%-40%) if two variables were present, and high risk (60%-90%) if three or more variables were present. We identified and quantified current risk factors for SNR and concluded that the risk of developing SNR during PCI in SVG can be predicted by simple clinical and angiographic variables obtained before PCI. This information may be useful when the risk of PCI has to be balanced against alternative strategies such as medical therapy or redo-bypass surgery or in the selection of those patients that will most benefit from the use of protection devices during PCI.

Intravascular ultrasound assessment of the stenoses location and morphology in the left main coronary artery in relation to anatomic left main length

Eighty-seven left main stenoses were evaluated by angiography and intravascular ultrasound. Intravascular ultrasound analysis included left main length (bifurcation to ostium), stenosis location, stenosis length, stenosis external elastic membrane, lumen, plaque & media cross-sectional area (CSA), plaque burden (plaque & media/external elastic membrane CSA), calcium arc, calcium length, eccentricity, and remodeling index (stenosis/reference external elastic membrane CSA). Long anatomic left main arteries (length > or =10 mm, n = 43) were compared with short anatomic left main arteries (length <10 mm, n = 44) regarding stenosis location. Ostial (proximal third of left main artery) (n = 32) and nonostial (midthird and distal third) stenoses (n = 55) were compared regarding stenosis morphology. Short anatomic left main arteries developed stenoses more frequently near the ostium (ostium 55%, bifurcation 38%). Conversely, long anatomic left main arteries developed stenoses more frequently near the bifurcation (ostium 18%, bifurcation 77%, p = 0.001). Ostial left main stenoses were more common in women (44% vs 20%, p = 0.02), had larger lumen area (6.2 +/- 2.2 vs 4.6 +/- 2.3 mm(2), p = 0.002), less plaque burden (62 +/- 15% vs 80 +/- 9%, p <0.0001), less calcification (arc = 78 +/- 65 degrees vs 195 +/- 101 degrees, p <0.0001), and more negative remodeling (remodeling index = 0.87 +/- 0.19 vs 1.01 +/- 0.21, p = 0.005) than nonostial left main stenoses. Most ostial left main stenoses were categorized as eccentric (97% vs 76%, p = 0.01). Short and long left main arteries develop stenoses at different locations. Stenosis morphology was significantly different in these 2 locations.

Localizing role of hemodynamics in atherosclerosis in several human vertebrobasilar junction geometries

Atherosclerosis is a common finding in the vertebrobasilar junction and in the basilar artery. Several theories try to link the process of atherogenesis with the forces exerted by the flowing blood. An attractive relation has been found between the locations in vessels at which atherosclerotic plaques are often present and the locations in models where complicated flow patterns exist. Most of the studies provided data on bifurcations. Finding a similar relation in an arterial confluence would certainly add to the credibility of the (causal) relationship between hemodynamics and atherosclerosis. Further support can be provided if variations of the geometry result in changes of the location of the atherosclerotic lesions, corresponding to the changes of the flow force distribution. In our previous numerical and experimental work, the influence of geometric and hemodynamic parameters, such as asymmetrical inflow, confluence angle, and blunting of the apex, on the flow in vertebrobasilar junction models has been investigated in detail. Recirculation areas and distribution of the wall shear stress have been computed. In this anatomic study, the effect of modulation of these geometric and hemodynamic parameters on the flow pattern is compared with the size and location of plaques in human vertebrobasilar junctions and basilar arteries. In addition, a comparison is made between the preferential areas of atherosclerotic plaques in junctions and bifurcations to demonstrate the localizing role of hemodynamics in atherogenesis. The apex of the vertebrobasilar junction and the lateral walls of the basilar artery appeared to be prone to atherosclerosis. In 43 of 85 vertebrobasilar junctions, a plaque was found at the apex. Furthermore, the summed plaque thickness at both lateral walls differs significantly (paired t test, P=.03) from that at the walls facing the pons and the skull base. In contrast, several authors found that the lateral walls of the mother vessel and the apex in bifurcations are often spared. Modulation of the various parameters in the models changed the size of the regions with low wall shear stress and/or recirculation areas dramatically. A comparable effect was found in the occurrence of plaques in the human vertebrobasilar junction; eg, for an atherosclerotic plaque at the apex, a predicted probability larger than 0.5 was computed for blunted apexes and for sharp-edged apexes with a confluence angle exceeding 90 degrees. Apparently, two geometric risk factors for an atherosclerotic plaque at the apex can be distinguished: a blunted apex and a large confluence angle.

Influence of the Geometry of the Left Main Coronary Artery Bifurcation on the Distribution of Sudanophilia in the Daughter Vessels

Uptake of circulating albumin by the aortic wall is greater downstream than upstream of branches in immature rabbits, but the opposite pattern occurs in mature animals. We investigated the role of NO in determining these variations. Descending thoracic aortas of rabbits were cannulated using techniques that avoid depressurization, overstretching, and excessive fluid dynamic stresses at the endothelial surface. They were perfused in situ at a constant pressure and flow rate with oxygenated, protein-containing physiological buffer, with or without N w -monomethyl-L-arginine, an inhibitor of NO synthesis. Aortas were fixed 7 to 8 minutes after the addition of rhodamine-labeled albumin to this perfusate, and uptake of the tracer near intercostal ostia was measured by digital imaging fluorescence microscopy of sections through the wall. Despite the absence of pulsatile flow, blood cells, and many plasma components, patterns of transport in control experiments were the same as those occurring in vivo; uptake was greatest downstream of ostia in immature vessels and upstream in mature ones, although mean uptake was higher than previously reported. In the presence of the inhibitor, mean uptake in immature arteries was elevated threefold and the maximum tracer concentration occurred deeper in the wall, but there was no change in the fractional difference between regions. Conversely, the reverse of the control pattern of transport was observed in mature arteries exposed to the inhibitor, but there was no change in mean uptake. The reversal was almost entirely prevented by adding excess L-arginine to the perfusate and was largely stereospecific. Endogenous NO thus appears to determine the mature pattern of transport near branches and helps to maintain the barrier function of the immature wall. ( Arterioscler Thromb Vase Biol. 1997;17:1361-1368.)

Relationship between the geometry and quantitative morphology of the left anterior descending coronary artery

The well established 'systemic' risk factors for atherosclerosis can explain only half of the variability in its occurrence. To account for some of the remaining variability, it was suggested that certain geometric features of atherosclerosis-prone segments ('geometric risk factors') can increase the likelihood of disease locally through their influence on the hemodynamic environment of the vessel wall. Since this mediation might elicit early morphological changes in the artery, relationships were sought between the histomorphometry and axial geometry of the left anterior descending (LAD) coronary arteries of 15 angiographically lesion-free human hearts obtained at autopsy. Geometric variables were quantified by image processing of multiplane angiograms of the hearts, and morphometry was obtained from transverse histologic sections at 91 sites. The results show that: (1) total intimal and medial area are negatively correlated with the distance from the site to the origin of the LAD; (2) the angle of the branch immediately proximal to the site is positively correlated with most of the intimal and medial variables, and appears to have a major influence on the intima; (3) the area ratio of the immediately proximal branch is correlated primarily with medial variables; and (4) local curvature is correlated only with the maximum thickness of the intima and media. These observations suggest that there are significant relationships between arterial geometry and vascular morphology prior to the development of frank disease.

Percutaneous revascularization of ostial saphenous vein graft stenoses

OBJECTIVES

This study sought to evaluate the short-term results and long-term outcome of percutaneous revascularization of ostial saphenous vein graft stenoses in a large patient series.

BACKGROUND

Previous studies have demonstrated that the results of balloon angioplasty for native coronary ostial stenoses are significantly worse than those for nonostial lesions. However, it is controversial whether interventions in patients with ostial saphenous vein grafts carry a similar prognosis.

METHODS

We identified 68 consecutive patients with ostial (group I) and 72 consecutive patients with proximal, nonostial (group II) saphenous vein graft stenoses who underwent percutaneous angioplasty or directional atherectomy for a single new stenosis at the Cleveland Clinic between 1986 and 1992.

RESULTS

Success was achieved in 61 patients (89.7%) in group I and 64 (88.9%) in group II (p = 0.88). There were no differences in major procedural complications (death, Q wave infarction and bypass surgery) between the two groups. At a mean (+/- SD) follow-up of 23 +/- 17 months, 36 patients (64%) in group I had one or more adverse events (death, infarction, repeat coronary revascularization or cardiac-related hospital admission) compared with 34 patients (58%) in group II (p = 0.87). Twenty-eight patients (50%) were angina free in group I compared with 33 (56%) in group II (p = 0.65). During the follow-up period in group I, 7 patients died (13%), 10 had a myocardial infarction (18%), 11 had repeat bypass surgery (20%), 8 had repeat percutaneous interventions (14%), and 30 had one or more cardiac-related hospital admissions (54%). The incidence of these events was similar in group II except for a slightly higher incidence of myocardial infarction: 6 patients died (10%), 3 had a myocardial infarction (5%), 12 had repeat bypass surgery (20%), 12 had repeat percutaneous interventions (20%), and 26 had one or more cardiac-related hospital admissions (44%).

CONCLUSIONS

Unlike ostial native coronary disease, the clinical, procedural and follow-up profile of ostial saphenous vein graft revascularization is not significantly worse than proximal nonostial disease. This finding may be related to the overall suboptimal results of percutaneous revascularization in saphenous vein grafts compared with native coronary arteries or to the unfavorable intrinsic properties of ostial native coronary arteries compared with ostial vein grafts.

Rotational coronary atherectomy with adjunctive balloon angioplasty for the treatment of ostial lesions

Conventional balloon angioplasty (PTCA) of ostial lesions (OL) is associated with suboptimal results and a higher complication rate. Partial plaque ablation with rotational atherectomy (RA) before PTCA might improve results. This approach was used in 63 patients (pts) (mean age 64 +/- 10 yrs; 44 men, 19 women) with 69 OL. There were 15 aorto-OL and 54 branch-OL. Calcification was more frequent in aorto-OL than in branch-OL (67% vs. 35%, P < 0.05). Mean burr size was 1.8 +/- 0.3 mm. Burr-artery ratio was 0.74 +/- 0.10. Adjunctive PTCA was systematically performed. Procedural success was achieved in 58 pts (92%): 14 aorto-OL (93%) and 50 branch-OL (93%) were successfully treated; major complications occurred in 1 (7%) aorto-OL and 1 (2%) branch-OL. Uncomplicated failure occurred in three cases. Minimal lumen diameter (MLD) increased from 0.69 +/- 0.31 mm before RA to 1.43 +/- 0.28 mm after RA (P < 0.001) and 2.16 +/- 0.29 mm after PTCA (P < 0.001). Diameter stenosis (DS) decreased from 75 +/- 13% before RA to 32 +/- 12% after RA (P < 0.001) and 14 +/- 10% after PTCA (P < 0.001). All successfully treated pts underwent repeat angiography 24 h later and exercise testing or repeat cardiac catheterization > 6 mo later. At 24 h repeat angiography, DS was 17 +/- 15% (P = NS vs. after PTCA); no lesion had a DS > or = 50%. Follow-up coronary angiography was performed in 30 pts (52%) who had abnormal stress testing: 13 pts (43%) showed angiographic restenosis in at least one successfully treated OL. (ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of the geometric parameters of the aortic bifurcation from magnetic resonance images

This paper presents a method for measuring arterial geometry in vivo using MRI. The approach was validated using MR images of three perfused compliant casts of human aortic bifurcations whose geometry was known. Preliminary human studies demonstrated the reproducibility of the technique. The approach was applied to 20 normal individuals to study the effects of age, race, and gender on the geometry of the aortic bifurcation. The results show that older people tend to have a smaller bifurcation angle, lower planarity, and larger angular asymmetry than younger people. Asians have larger bifurcation angles than whites. The bifurcation of males is more asymmetric than that of females. These results may have implications regarding the heritability of arterial geometry, the similarities of cardiovascular risk within families, and differences in risk among groups.

Variability of human coronary artery geometry: an angiographic study of the left anterior descending arteries of 30 autopsy hearts

A computer-based system is described to measure objectively the geometric parameters of arteries from pairs of projection angiograms. This technique, which employs back-projection to define the vessel axes in 3-D space, was used to obtain selected parameters of coronary artery geometry from radiographic images of autopsy hearts. Results of the first 30 cases are presented, focussing on the distribution of the geometric parameters of the left anterior descending coronary artery (LAD) and its first two major branches. The derived parameters include the angle between the left circumflex artery and the LAD; the angles between the LAD and its early diagonal and septal perforator branches; distances between branch points; and tortuosity. The geometric parameters vary considerably, presumably contributing to a corresponding variability in local hemodynamic and mechanical stresses. Most parameters are uncorrelated. One exception is the angle at the origin of the second diagonal branch, which is positively correlated (p < 0.01) with the distance between the ostia of the first two diagonal vessels; this correlation could reflect the existence of "target" perfusion regions. No relation between geometric parameters and age or gender was seen. In this sample, blacks had a larger angle at the left main bifurcation than whites (p < 0.05).

Initial experience with excimer laser angioplasty for coronary ostial stenoses

The excimer laser has several potential advantages over conventional balloon angioplasty in the management of stenoses of the native coronary arteries and of the ostia of saphenous vein grafts. Its use in nine patients, eight of whom were classed as high risk, is described. Four lesions involved the ostia of saphenous vein grafts, three of protected left main stems, and two of native right coronary arteries. Stand alone laser was used in seven cases and laser with additional balloon angioplasty was used in two vein graft stenoses. Acute laser success was achieved in all cases, with a mean reduction of stenosis from 82% to 34% after laser alone and to 28% when balloon angioplasty was used as well. One patient died during laser angioplasty to a non-ostial lesion (procedural success rate 89%) and a second died ten weeks after the procedure. In one patient recurrent angina developed (clinical recurrence rate 25%) and restenosis was confirmed on angiography. Follow up angiography was also performed on the other six surviving patients, all of whom were symptom free and none of whom showed evidence of significant restenosis (restenosis rate 14%). With a mean follow up of 19.7 months the overall success rate was 67%.

Relation between coronary artery geometry and the distribution of early sudanophilic lesions

The relationship between the angle formed by the left circumflex (LCX) and left anterior descending (LAD) coronary arteries at the bifurcation of the left main coronary artery (LM) and the location of sudanophilia in the proximal portions of the LCX and LAD, was investigated, using a normalized index of disease severity (relative proximal involvement, RPI) to isolate the local effect of geometry on the predisposition to disease from that of other risk factors. Multiplane angiograms of the left coronary artery system of 15 hearts were digitized and processed to form a three-dimensional representation of the centerline of the lumen (termed the 'axis') of each coronary segment; the LM branch angle was objectively computed from the reconstruction. The coronary vessels were fixed in situ, removed from the hearts, opened longitudinally and stained with Sudan IV. The RPIs of the LAD and LCX were obtained by dividing the percentage sudanophilia seen en face in the first 1 cm of each vessel by the percentage sudanophilia in the first 5 cm. RPI was correlated negatively with LM branch angle, suggesting that a small LM branch angle may be a 'geometric risk factor' for proximal atherosclerotic disease in the daughter vessels. The correlation was stronger for the LCX than the LAD. These results would appear to be consistent with the notion that atherosclerosis is favored where a larger extent of the vessel experiences fluid dynamic wall shears near zero for an appreciable part of the pulsatile cycle.

Impedance matching at arterial bifurcations

Reflections of pulse waves will occur in arterial bifurcations unless the impedance is matched continuously through changing geometric and elastic properties. A theoretical model is presented which minimizes pulse wave reflection through bifurcations. The model accounts for the observed linear changes in area within the bifurcation, generalizes the theory to asymmetrical bifurcations, characterizes changes in elastic properties from parent to daughter arteries, and assesses the effect of branch angle on the mechanical properties of daughter vessels. In contradistinction to previous models, reflections cannot be minimized without changes in elastic properties through bifurcations. The theoretical model predicts that in bifurcations with area ratios (beta) less than 1.0 Young's moduli of daughter vessels may be less than that in the parent vessel if the Womersley parameter alpha in the parent vessel is less than 5. Larger area ratios in bifurcations are accompanied by greater increases in Young's moduli of branches. For an idealized symmetric aortic bifurcation (alpha = 10) with branching angles theta = 30 degrees (opening angle 60 degrees) Young's modulus of common iliac arteries relative to that of the distal abdominal aorta has an increase of 1.05, 1.68 and 2.25 for area ratio of 0.8, 1.0 and 1.15, respectively. These predictions are consistent with the observed increases in Young's moduli of peripheral vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency of success and complications of coronary angioplasty of a stenosis at the ostium of a branch vessel

The authors of this study hypothesized that percutaneous transluminal coronary angioplasty of a stenosis at the ostium of a branch vessel, whether isolated or associated with a bifurcation stenosis, was associated with reduced procedural success and increased in-hospital complications. One hundred six patients with 119 ostial branch stenoses were compared with 1,168 patients who underwent angioplasty of nonostial branch stenoses. An ostial branch stenosis was defined as a stenosis in the proximal 3 mm of a major branch vessel (diagonal [n = 58], posterior descending [n = 21], obtuse marginal [n = 34] and intermediate [n = 6]). The ostial branch stenosis was isolated in 61% of the patients and associated with a bifurcation stenosis in 39%. Despite a balloon to artery ratio of 1.05:1, angiographic success was 74% of ostial branch stenoses versus 91% of nonostial stenoses (p less than 0.01). Furthermore, angioplasty of ostial branch stenoses resulted in a complication rate of 13 versus 5% for angioplasty of nonostial branch stenoses (p less than 0.01). Therefore, angioplasty of ostial branch stenoses results in decreased procedural success and significant residual stenosis despite adequate balloon sizing, suggesting arterial elastic recoil and a significant increase in complications.

Restenosis after percutaneous transluminal coronary angioplasty: the Emory University Hospital experience

Restenosis after coronary angioplasty, a gradual encroachment of the dilated arterial lumen by overgrowth of neointimal cells, occurs in a minority (25% to 30%) of patients. Clinical and anatomic descriptors of those patients who develop restenosis have been identified and suggest a complex, multifactorial etiology. Optimal initial enlargement of the diameter probably reduces the chance of restenosis on geometric grounds alone. The independent predictive value of a low final translesional pressure gradient indicates that adequate blood flow may reduce platelet adhesion and thrombus formation. The importance of the latter factor remains uncertain. Individual proliferative responses to the intimal and medial injury caused by balloon dilatation appear to be modulated by both lesion-specific and patient factors. Lesion-specific factors appear most important and relate to vessel site, tortuosity and branching. These factors are also thought to influence native atherogenesis but the relation between restenosis and atherogenesis remains obscure. Patient risk factors for coronary artery disease also appear to influence restenosis. Procedural factors and risk factor modification may partially modify the restenosis response; however, prevention of restenosis will depend on finding agents that block either stimulation or proliferation of smooth muscle cells.

Percutaneous coronary angioplasty: technique, indications, and results

The simplicity, safety, and economic advantages of percutaneous transluminal coronary angioplasty (PTCA) over coronary bypass surgery have encouraged its wide use as an alternative revascularization procedure. Four major problem areas require solutions before the technique fulfills its potential. First, PTCA technology requires further development to enhance success rates in severe, old, calcified lesions and in chronic total occlusions. Second, acute vessel reclosure needs intensive study to determine how this important complication can be foreseen and effectively managed if not avoided entirely. Third, effective treatment strategies for patients with multivessel disease require definition. Finally, the problem of late lesion recurrence needs to be solved. Until these goals are achieved, the general practice of PTCA should be restricted to treatment of early-stage coronary artery disease, single-vessel, or discrete two- and three-vessel disease.

Restenosis after successful coronary angioplasty in patients with single-vessel disease

To determine risk factors for restenosis, we studied 998 patients who underwent elective coronary angioplasty (PTCA) to native coronary arteries between July 1980 and July 1984. Restenosis, defined as a luminal narrowing of greater than 50% at follow-up, was present in 302 patients (30.2%). Univariate analysis of 29 factors revealed seven factors related to restenosis: vessel dilated (circumflex coronary artery 18%, right coronary artery 27%, left anterior descending artery 34%; p less than .01), final gradient of 15 mm Hg or less compared with greater than 15 mm Hg (27% vs 38%, p less than .01), duration of angina greater than 2 months compared with angina of shorter duration (27% vs 35%, p = .01), post-PTCA stenosis of 30% or less compared with 31% to 50% (28% vs 36%, p less than .025), stable vs unstable angina (26% vs 34%, p less than .05), presence vs absence of intimal dissection (26% vs 32%, p = .07), and female gender vs male gender (25% vs 32%, p = .08). Multivariate analysis revealed five factors independently related to increased risk of restenosis in the following order of importance: PTCA in the left anterior descending artery, absence of intimal dissection immediately after PTCA, final gradient greater than 15 mm Hg, a large residual stenosis after PTCA, and unstable angina. Restenosis after PTCA is a multifactorial problem. The hemodynamic and angiographic result at the time of PTCA significantly influences long-term outcome, but additional measures aimed at reducing the rate of recurrence of atherosclerotic plaque are required.

Distribution of the geometric parameters of human aortic bifurcations

The distribution of flow divider offset, branch angle, and angular asymmetry in a collection of 70 human aortic bifurcations are reported. A computer algorithm was used to determine these parameters objectively. The mean values with standard deviations and ranges are: 1) magnitude of flow divider offset = 1.4 +/- 1.4 mm (range = 0.04 to 8.1 mm); 2) branch angle = 35.0 degrees +/- 11.1 degrees (range = 10.4 degrees to 61.3 degrees); and 3) angular asymmetry = 15.3 degrees +/- 12.9 degrees (range 0.2 degrees to 56.1 degrees). Since these parameters have been shown to have a significant influence on hemodynamic shear, their variability suggests a corresponding variability in the fluid dynamic stresses to which the bifurcations were exposed in life.

Role of platelets and thrombosis in coronary atherosclerotic disease and sudden death

During the last decade, significant advances have been made in the understanding of the pathogenesis of coronary atherosclerotic disease. Two facts are important: 1) the early and some of the advanced coronary atherosclerotic lesions progress very slowly, probably by means of a complex stepwise biologic process with one of the steps being an interaction between platelets and the arterial wall; the process can be favored by the so-called risk factors of atherosclerotic disease, and 2) some of the advanced coronary atherosclerotic lesions progress very rapidly, probably by means of complicating anatomic events, one of which is related to a thrombogenic process. From a clinical point of view, technologic improvements, such as serial coronary arteriography, reperfusion during the acute coronary artery syndromes, postmortem coronary arteriography, and methods for serial histopathologic and histochemical studies, have brought to light the clinical importance of the processes of plaque rupture, dissecting hemorrhage and, most important, thrombosis. These complicated processes appear to be of paramount importance in the pathogenesis of some of the acute coronary syndromes including unstable angina, myocardial infarction and sudden coronary death. Antithrombotic and platelet inhibitor therapy is under investigation and appears promising in some of these patient subsets.

Prevalence of angiographically recognizable atherosclerosis in non-dominant right coronary arteries

Among 1,000 consecutive patients referred for coronary arteriography because of chest pain, 89 patients were found to have a non-dominant right coronary artery (NDRCA). These patients were compared to 89 consecutive patients with dominant right coronary artery (DRCA) matched for age, sex, smoking and serum cholesterol. There was a lower incidence of obstructive disease in NDRCA (23 of 89 patients, 26%) than in DRCA (55 of 89 patients, 62%), X2 = 23.368, p less than 0.001. The incidence of coronary disease was also lower in the NDRCA group, 50 of 89 patients (56%), than in the DRCA group, 68 of 89 patients (76%), X2 = 8.146, p less than 0.01. When only patients with coronary artery disease (CAD) were included in the analysis: 23 of 50 (46%) patients with CAD and NDRCA had obstructive disease in the right coronary artery (RCA) while 55 of 68 (80%) patients with DRCA and CAD had obstructive disease in the RCA, X2 = 15.646, p less than 0.001. The lower incidence of disease in NDRCA persisted even when only the proximal one-third of the DRCA was considered: 41 of 89 (46%) patients with DRCA had proximal lesions compared to the total length of NDRCA, 23 of 89 patients (26%), X2 = 7.940, p less than 0.01.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of lesions in the coronary circulation

The location of coronary artery narrowings in coronary disease (CAD) is of considerable importance in assessing the mass of myocardium at risk as well as patient prognosis. The detailed distribution of coronary lesions was mapped in 302 patients with CAD who had coronary angiography for chest pain. All identifiable coronary lesions were measured manually and the site and degree of narrowing were stored in a computer-based multisegmental model of the coronary tree. A high prevalence of CAD was found in proximal vessels and especially at, or adjacent to, proximal points of branching. In the left anterior descending coronary artery, the lesions were most prevalent immediately after the first diagonal branch and at the origin of this branch. In the right coronary artery, there was a high prevalence of narrowing between the infundibular and acute marginal branches and specifically around the origin of the right ventricular branch. In the left circumflex coronary artery, there was a predilection for narrowing in and around the origin of the first marginal branch. When a ramus intermedius was present, its origin was frequently the site of narrowing.

Accelerated atherosclerosis in subjects with some minor deviations from the common type of distribution of human coronary arteries

Gross dissection of the coronary arteries of 566 subjects aged 0--45 years from an unselected population sample of Bucharest revealed the presence of a similar anatomical branching pattern in 58% of cases. Starting from this common type of distribution of coronary arteries, some minor deviations were detected coexisting with a thicker intima, a more rapid onset and evolution of atherosclerotic plaques, and a more important degree of luminal obstruction. Among the 15 minor deviations described in this paper, 3 were constantly associated, 9 only occasionally associated and 3 not associated with an accelerated atherosclerosis. The most important of these atherogenic deviations was present in 29% of cases or in 1 out of every 3 or 4 subjects. In essence, these deviations consisted of an excessive increase in external diameter and length of the left coronary arterial system, coexisting with an underdeveloped right coronary arterial system, or vice versa. The atherogenic deviations from the common type of distribution of the coronary arteries seemed to represent an important genetically transmitted risk factor for coronary heart disease.