Theoretical study of the flow rate toward the right heart territory in case of total occlusion of the right coronary artery

In this work, patients with severe coronary disease and chronic occlusion of the right coronary artery (RCA) are studied. In this clinical situation, the collateral circulation is an important factor in the preservation of the myocardium until reperfusion of the area at risk. An accurate estimation of collateral flow is crucial in surgical bypass planning as it can influence the outcome of a given treatment for a given patient. The evaluation of collateral flow is frequently achieved using an index (CFI, Collateral Flow Index) based on pressure measurements.Using a model of the coronary circulation based on hydraulic/electric analogy, we demonstrate, through theoretical simulations, that a wide range of fractional collateral flow values can be obtained for any given distal pressure difference depending on the values of the capillary and collateral resistances.     

超声二次谐波声面声学造影评价冠脉的微血管血流灌注

目的：本文获取冠状动脉血流变化所致的心肌灌注类型,以了解冠脉的微血管血流灌注变化。方法：36人先后完成冠状动脉影,静脉注射声学造影剂利声显（Levovist),通过超声二次谐波技术获取心肌灌注图像,按心肌灌注积分指数将病人分为三组。结果：三组病人的冠状动脉狭窄程度、心肌灌注积分指数明显差异（P＜0．001）,冠状动脉狭窄波＜75％者,病人心肌灌注多为正常,随着冠状动脉狭窄程度加重,出现不同程度的心肌灌注异常。8例完全阻塞的冠状动脉有不同的冠状动脉侧支循环表现为不同的心肌灌注类型。结论：静脉心肌声学造影是反映心肌灌注的有效方法,能够反应冠状动脉血流的改变及微循环结构的完整性变化,从而弥补冠状动脉造影仅能显示心外膜下的冠状动脉而无法观察毛细血管水平的心肌灌注之缺限。当心肌灌注不良时,MCE能提示冠状动脉病变的存在,及其严重性,但要注意侧支循环对心肌灌注之影响,可影响对冠脉病变程度判断的精确性。冠状动脉造影确定某支冠脉病变时,MCE心机灌注有助于评价侧支循环状态。     

Effect of intracoronary shunt on right ventricular function during off-pump grafting of dominant right coronary artery with poor collateral

Although numerous studies have validated the efficacy of intracoronary shunt on reducing left ventricular dysfunction during off-pump coronary artery bypass surgery (OPCAB), there is lack of evidence supporting its role on right ventricular (RV) function during right coronary artery (RCA) revascularization. Therefore, we studied the effect of intracoronary shunt during grafting of dominant RCA without visible collateral supply on global RV function using thermodilution method. Forty patients scheduled for multivessel OPCAB with right dominant coronary circulation without collateral supply confirmed by angiography were randomized to RCA revascularization either with a shunt (n=20) or soft snare occlusion (n=20). RV ejection fraction (RVEF) was recorded at baseline, during RCA grafting, and 15 min after reperfusion. Corresponding RV stroke work index (RVSWI) was calculated. RVEF and RVSWI decreased significantly during RCA grafting and returned to baseline values after reperfusion in both groups without any significant differences between the groups. Intracoronary shunt did not exert any beneficial effect on global RV function during RCA grafting, even in the absence of visible collateral supply. Regarding the possibility of graft failure by intracoronary shunt-induced endothelial damage, routine use of intracoronary shunt during RCA grafting is not recommended in patients with preserved biventricular function.     

A very rare anatomic variation of the right ventricular branch: right ventricular descending branch from the anterior interventricular branch

The anterior interventricular branch of the left coronary artery has the most constant distribution in the human heart and rarely gives off right ventricular branches. Here we report a case with a right ventricular branch which diverged from the anterior interventricular branch and descended on the anterior right ventricular wall parallel to the anterior interventricular sulcus; we termed it the right ventricular descending branch. This artery gave a collateral artery to the occluded anterior interventricular branch at the apex, and had prevented anterior myocardial infarction. The right ventricular descending branch should be precisely identified in order to perform successful myocardial revascularization procedures such as coronary artery bypass grafting and percutaneous coronary intervention, especially in a patient with anterior interventricular branch occlusion.     

Anatomic variant of the posterior interventricular coronary artery: Implications for coronary angioplasty in acute myocardial infarction

Acute thrombotic occlusion of an infarct-related artery is frequently found in patients presenting with myocardial infarction. In a patient with acute inferior wall myocardial infarction complicated by continuous chest pain and hemodynamic instability, emergency diagnostic coronary arteriography demonstrated a patent, infarct-related, “pseudo” right coronary artery while, in fact, this vessel was a rare anatomic variant of the posterior interventricular branch with very early origin from the right coronary artery and the true right coronary artery was completely occluded by a thrombotic obstruction. Accurate anatomic-angiographic interpretation of the angiogram was crucial for successful performance of emergency recanalization and revascularization of the true right coronary artery with laser and balloon angioplasty. Once antegrade flow was restored another rare coronary variant was discovered, i.e., a sinoatrial node artery arising from the middle portion of the newly patent right coronary artery. Clin. Anat. 10:303–306, 1997. © 1997 Wiley-Liss, Inc.     

冠心病患者冠状动脉侧支循环的形成与PDGF mRNA水平的关系

目的:探讨冠心病患者单核细胞血小板源性生长因子(PDGF)与冠状动脉侧支循环的关系。方法:依据选择性冠状动脉造影结果将64例患者分为对照组(非冠心病患者,n=15)、冠心病不伴侧支循环组(n=31)、冠心病伴侧支循环组(n=18),采用RT-PCR技术检测3组患者主动脉根部血液及股动脉血液中单核细胞PDGFmRNA水平。结果:(1)冠心病患者有、无侧支循环组之间的冠状脉动病变程度、不稳定心绞痛及心肌梗死发生率无显著差异(P>0.05);但无侧支循环患者心功能不全、室壁瘤的发生率显著增加(P<0.01);(2)与对照组相比,冠心病患者主动脉根部血液单核细胞PDGFmRNA水平增加(P<0.01);有侧支循环患者增加更为显著(P<0.01);而冠心病患者股动脉血液中单核细胞PDGFmRNA水平显著增加(P<0.01),有无侧支循环者之间无显著差别(P>0.05)。结论:冠状动脉侧支循环的建立可显著降低心肌梗死后心功能不全、室壁瘤的发生;PDGFmRNA水平增加与冠状动脉侧支循环形成密切相关;侧支循环形成与否可能主要取决于病变冠状动脉局部单核细胞PDGF基因水平;单核细胞PDGF基因水平可作为评价冠心病患者预后好坏的指标之一。     

A more sensitive pressure-based index to estimate collateral blood supply in case of coronary three-vessel disease

With progressive occlusion of a coronary main artery, some anastomotic vessels are recruited in order to supply blood to the ischemic region. This collateral circulation is an important factor in the preservation of the myocardium until reperfusion of the area at risk. An accurate estimation of collateral flow is crucial in surgical bypass planning as it alters the blood flow distribution in the coronary network and can influence the outcome of a given treatment for a given patient. The evaluation of collateral flow is frequently achieved using an index based on pressure measurements. It is named Collateral Flow Index (CFI) and defined as: (P(w)-P(v))/(P(ao)-P(v)), where P(w) is the pressure distal to the thrombosis, P(ao) the aortic pressure and P(v) the central venous pressure. We propose here another index, that is more sensitive to the P(w) value and could thus describe the role of collateral flow with more precision. We illustrate this idea using some clinical pressure measurements in patients with severe coronary disease (stenoses on the left branches and total occlusion of the right coronary artery).     

Functional Development of the Coronary Collateral Circulation During Coronary Artery Occlusion in the Conscious Dog

We studied changes in the coronary collateral circulation during coronary artery occlusion in 14 conscious dogs by: a) determining simultaneous changes in peripheral coronary pressure (PCP) and retrograde flow (RF) after abrupt coronary artery occlusion; b) correlating these functional indices with quantitative anatomic indices (AI) of coronary collateral development (Menick et al: Am Heart J 82:503-510, 1971); and c) observing changes in these indices after repeated reocclusions of a coronary artery. These dogs were subjected to left circumflex coronary artery (LCCA) occlusions for 2 hours to 8 days; pressure tubes were implanted in the aorta and LCCA, the latter tube placed distal to an occlusive cuff for PCP and RF measurements. Afterwards the animals were sacrificed, their hearts injected with a modified Schlesinger's gelatin mass, and AI determined. During 2 to 24 hour LCCA occlusions (11 dogs) mean PCP rose to levels 50 to 80% of prevailing aortic pressure. During repreated 2- to 24-hour occlusions (2 dogs) in the same dog, the rate at which PCP rose increased. Retrograde flow was unchanged during 2- to 24-hour occlusions. Anatomic indices of these dogs were in the same range as those observed in unoccluded controls. When LCCA occlusion was maintained for more than 4 days (3 dogs), mean PCP rose during the first 24 hours and then remained stable; RF did not change until 4 days into occlusion and then increased. Anatomic indices of dogs occluded for more than 4 days were significantly greater (P < 0.001) than those of the 2- to 24-hour occlusion groups. Our study shows that: a) the early PCP rise after occlusion is not associated with an increase in RF, b) RF is a better index of collateral function and c) RF correlated well with the anatomic development of the collateral bed.     

Anomalous first septal perforator artery: Anatomic-clinical correlates

The interventricular septum is considered the most densely vascularized portion of the heart, containing important elements of the cardiac conduction system and providing mechanical support for both right and left ventricular function. Anatomically, this structure is perfused by the relatively small caliber anterior and posterior septal perforator branches arising from two large epicardial coronary vessels, the anterior interventricular (descending) branch of the left coronary artery and the posterior interventricular (descending) branch of the right coronary artery, respectively. In cases of significant atherosclerotic disease depriving flow in the major coronary vessels and their septal branches, an anomalous septal perforator artery can take over the task of supporting the function of the interventricular septum by supplementing essential collateral flow. © 1996 Wiley-Liss, Inc.     

Septal collateralization: Demonstration of canine intramyocardial collaterals

The anatomical distribution of intra-myocardial collateral arteries that develop from the septal to the other major coronary arteries was studied in dogs following gradual Ameroid occlusion of tftt circumflex artery. The septal artery was cannulated and injected with Batson's plastic compound resulting in a cast of the coronary circulation. Collateral vessels radiated from the septal vascular bed to both the circumflex and anterior descending arteries. The collaterals developed from the entire base-to-apex extent of the septal artery and were found on both the right and left sides of the septum. Collateral growth appeared to be more concentrated at the apex of the heart. The anatomical details of septal collateral circulation illustrate the importance of intramyocardial collateralization in the dog, which was thought to exhibit primarily epicar-dial collaterals.     

Arterial vascularization of the human moderator band: an analysis of this structure's role as a collateral circulation route

In the human heart, the moderator band, or trabecula septomarginalis, is a muscle column that courses inferiorly from the right portion of the interventricular septum to the base of the anterior papillary muscle of the right ventricle This muscular structure is crossed by one or more arteries, which come from the anterior interventricular artery and perfuses the anterior papillary muscle of the right ventricle. In order to clarify the arterial supply of this muscle column, we studied 28 adult hearts, free of any signs of coronary disorder. The path of the moderator band artery was followed by means of microdissection, and we studied the source, course, and interconnections made with other arteries. We observed that the source of the moderator band artery lies in the first three anterior septal arteries, most often in the second one. In relation to the short axis of the heart, the artery of the moderator band can either follow a horizontal path to the septal papillary muscle of the right ventricle or an oblique route to the moderator band, depending on the position of its source. In all the hearts studied, the moderator band artery made anastomotic connections at the base of the anterior papillary muscle of the right ventricle with various branches of the right coronary artery, which means that it can play a key role in collateral circulation following obstruction of the epicardium coronary arteries.     

冠状动脉造影和三磷酸腺苷负荷超声心动图对川崎病冠状动脉损害远期追踪的价值

目的探讨选择性冠状动脉造影及三磷酸腺苷负荷超声心动图对川崎病（KD）冠状动脉损害远期追踪的价值。方法选取1999至2007年广州市儿童医院KD急性期超声心动图检查发现合并冠状动脉损害的患儿,同时采用三磷酸腺苷负荷超声心动图及选择性冠状动脉造影于恢复期进行远期随访。结果依据纳入标准和排除标准逐层筛选,确定9例KD患儿为本研究的样本。男8例,女1例,急性期发病年龄为1-10岁,平均（4.44±3.09）岁。检查时年龄4-12岁,平均（7.89±2.62）岁。追踪时间1.5~7年,平均（3.44±1.67）年。急性期超声心动图示9例患儿中冠状动脉巨瘤5例,冠状动脉瘤3例,冠状动脉扩张1例。三磷酸腺苷负荷超声心动图示：节段性室壁运动异常6/9例;冠状动脉血流储备下降5/9例。冠状动脉造影示：双侧主干冠状动脉瘤4例,同时伴远端动脉瘤3处,冠状动脉左前降支狭窄1处,并冠状动脉扭曲,狭窄或充盈缺损3处,附近侧支血管形成1处;左前降支动脉瘤、右冠状动脉闭塞伴侧支循环形成1例,冠状动脉扩张4例。与同期超声心动图检查比较,冠状动脉造影新发现冠状动脉远端瘤3处,右冠状动脉远端狭窄2处,左前降支狭窄1处,右冠状动脉闭塞伴侧支血管形成1例。5例三磷酸腺苷负荷超声心动图检查结果阳性者与冠状动脉造影比较：均发现相应冠状动脉支狭窄或充盈缺损表现;1例三磷酸腺苷负荷超声心动图检查结果阳性,冠状动脉造影仅见轻度冠状动脉扩张。结论KD合并冠状动脉损害特别是动脉瘤造成的心脏损害可长期存在。对于远期追踪观察KD患儿冠状动脉病变,三磷酸腺苷负荷超声心动图具无创、安全可靠的优点,是判断心肌缺血的重要方法;选择性冠状动脉造影可明确显示冠状动脉病变的位置、形态、数目及严重程度,特别对冠状动脉狭窄、闭塞及远端病变能做出准确的评估。两种方?     

Changes in Coronary Perfusion after Occlusion of Coronary Arteries in Kawasaki Disease

Purpose

Myocardial infarction in children with total occlusion of a coronary artery after Kawasaki disease is rare due to multiple collateral vessels. We aimed to investigate the changes in coronary perfusion associated with coronary artery occlusion after Kawasaki disease.

Materials and Methods

Eleven patients with coronary artery occlusion after Kawasaki disease were investigated. Serial coronary angiographies after total occlusion of a coronary artery were reviewed and the changes were described in all patients with additive information collected.

Results

The median age at the occlusion was 5.9 years old. The interval to occlusion was 6.2±6.9 years. Four left anterior descending coronary artery total occlusions and 10 right coronary artery total occlusions were detected. Immediate coronary artery bypass graft for left anterior descending coronary artery total occlusion made right coronary total occlusion occurred in all except one patient and the intervals thereof were 1 year, 1.8 years, and 4 years. Collaterals to the left coronary artery regressed after recanalization, while new collaterals to the right coronary artery developed. In three, collaterals to the right coronary artery decreased without recanalization without clinical signs.

Conclusion

The right coronary artery should be followed up carefully because of possible occlusion of new onset or changes in collaterals.     

Enhancement of angiogenesis as the basis of reparative morphogenesis in ischemic myocardial lesion

The formation of new blood vessels is essential for the reparation of ischemic tissue. Animal model studies of myocardial ischemia showed that cell transplantation, gene therapy, and application of growth factors are able to promote collateral circulation development. Subsequent clinical trials conducted with these methods used for treatment of coronary artery disease demonstrated the safety and clinical benefits of this novel therapeutic approach called therapeutic angiogenesis. This method of treatment of ischemic lesions associated with cardiovascular diseases opens new clinical options in the area of tissue regeneration.     

Multiple aortocoronary bypass without artificial circulation

Results of 145 surgeries for direct myocardial revascularization without artificial circulation are presented. FC III and IV angina of effort was diagnosed in 80.6% and 13.5% of the patients respectively, acute coronary syndrome in 6.5%, past myocardial infarction in 63.8%. Mean left ventricular ejection fraction (EF) prior to surgery was 48.7 +/- 5.1%; it was below 40% in 28.8% of the patients. Three- and two-vessel coronary disease was documented in 54.7% and 35.3% of the patients respectively; 10% of them presented with the affected anterior interventricular branch, 14% with the stenotic trunk of the left coronary artery. Mean revascularization index increased from 22 to 76. The frequency of complete autoarterial revascularization amounted to 42.7%. Sequential and composite grafts were used in 93 and 257 cases respectively. No patient experienced perioperative myocardial infarction, acute disturbance of cerebral circulation, acute renal or cardiac insufficiency. Immediate postoperative hemorrhage requiring resternotomy developed in 0.9% of the patients, 1.2% with suppurative complications needed additional surgical treatment. It is concluded that myocardial revascularization on a beating heart is an efficacious and reliable method ensuring good results in the immediate and late postoperative period. Its success first and foremost depends on the previously gained experience that permits to operate patients with severe multi-vessel coronary artery disease and various concomitant disorders and thereby correct combined pathological conditions. The available data give reason to consider each patients in need of aortocoronary bypass as a candidate for myocardial revascularization on a beating heart regardless of the character and extent of coronary lesions and anatomical feature of the coronary bed.     

Brain microvessels: factors altering their patency after the occlusion of a middle cerebral artery (Wistar rat).

The progression from ischemic injury to pannecrosis that occurs in the rat brain several hours after occluding a large artery may be partly attributable to a worsening of the circulation through the microvessels. The objective of this study was to quantitate selected structural changes involving astrocytes and endothelial cells within an area of focal brain ischemia created by the occlusion of a middle cerebral artery. The magnitude of these structural changes was correlated with alterations in the patency to a circulating macromolecule through the microvessels (< or = 15 mu in diameter) located within the territory of the occluded artery. One hundred eighty-five adult male Wistar rats had the right middle cerebral artery occluded after threading a nylon monofilament through the external carotid artery. Experiments were terminated by either cardiovascular perfusion or decapitation and immersion fixation at intervals ranging between 30 minutes and 7 days after the arterial occlusion. Randomly selected animals from each experimental subgroup were injected intravenously with horseradish peroxidase (molecular weight 44 kd) approximately 20 minutes before death. The progressive decline in the area fraction comprised by the vessels filled with horseradish peroxidase was preceded at 30 to 60 minutes by an increase in the surface area occupied (on a cross-section of a microvessel) by endothelial cells (both nucleus and cytoplasm). This was followed by an increase of 23.7% in the mean diameter of astrocytes nuclei and a decrease of approximately 35% in lumenal surface of the microvessels. These observations suggest that the occlusion of a large cerebral artery causes prompt swelling of endothelial cells and astrocytes; both of these early biological responses may interfere with erythrocyte circulation and oxygen delivery, which (after the arterial occlusion) are entirely dependent on the circulation provided by the collateral arterial connections. Through its interference with microvascular patency and oxygen delivery, cell swelling may influence the rate at which neurons become necrotic. In this model of brain infarct the number of necrotic neurons peaks approximately 72 hours after middle cerebral artery occlusion.(ABSTRACT TRUNCATED AT 400 WORDS)     

Atresia of left coronary ostium and left main coronary artery

An uncommon coronary anomaly incidentally found at autopsy of a 76-year-old woman is reported. There was no history of cardiovascular symptoms or clinical signs of ischemic heart disease. The autopsy disclosed that the patient had no left coronary ostium and that the left main coronary artery was atretic. However, the rest of the left coronary system, including the left anterior descending coronary artery and the left circumflex coronary artery, were intact in their normal positions. Arterial flow to the left coronary system was supplied by a dilated collateral vessel that originated from the right main coronary artery and coursed between the right ventricular infundibulum and the aorta. Our case suggests that atresia of the left coronary ostium and the left main coronary artery, often associated with death at an early age, may also be compatible with symptom-free longevity. Moreover, attention is focused on the nomenclature of single coronary anomalies.     

Technology in interventional cardiology: percutaneous transluminal coronary angioplasty

Percutaneous transluminal coronary angioplasty (PTCA) is now capable of providing myocardial revascularization in a majority of patients, but significant problems with the technique remain. It is unsuitable for dealing with diffuse coronary artery disease, chronically occluded vessels may be impossible to disobliterate, and disease of the distal coronary vessel may be difficult to reach with a balloon. Approximately 5 percent of all procedures may be complicated by acute occlusion of the target vessel, usually by dissection of the arterial intima, often resulting in a need for emergency coronary artery bypass surgery (CABG). Furthermore, there is recurrence of the dilated lesion--'restenosis'--in approximately 30 percent of cases in the first 3 to 6 months after PTCA. Advances in this technique, since its introduction in the mid 1970s, have been directed at making initial success more likely, obviating the need for emergency CABG, and reducing the incidence of restenosis.     

The relation between viable segments and left ventricular ejection fraction improvement

For patients with coronary artery disease and left ventricular dysfunction who undergo revascularization, it is important to estimate the left ventricular ejection fraction (LVEF) improvement after revascularization, as this is a strong indicator of the long-term outcome. Identification of viable segments from echocardiography has been considered a predictive sign of LVEF improvement. However, a quantitative relation between segmental function recovery and global ejection fraction improvement has not been established. There is a clinical need to determine parameters that are predictive to LVEF improvement. A cylindrical left ventricular model is proposed to establish the relation between segmental myocardial function and LVEF based on a 12-segment echocardiograph model. Model results show that LVEF improvement is directly related to the contraction ratio in normal segments and a weighted sum of the number of viable segments that recover to normal or hypokinetic, which is equal to a weighted sum of the change in wall motion scores. This new combined parameter is a better predictor of the amount of LVEF improvement than the total number of viable segments or preoperative ejection fraction. The predictive value of the model was illustrated in a group of four patients with coronary artery disease who underwent revascularization.     

The relationship of myocardial bridges to coronary artery dominance in the adult human heart

Myocardial bridging is recognized as an anatomical variation of the human coronary circulation in which an epicardial artery lies in the myocardium for part of its course. Thus, the vessel is 'bridged' by myocardium. The anterior interventricular branch of the left coronary artery has been reported as the most common site of myocardial bridges but other locations have been reported. The purpose of this study was to provide more definitive information on the vessels with myocardial bridges, the length and depth of the bridged segment, and the relationship between the presence of bridges and coronary dominance. Two hundred formalin-fixed human hearts were examined. Myocardial bridges were found in 69 (34.5%) of the hearts with a total of 81 bridges. One bridge was found in 59 of these hearts and multiple bridges were observed in ten (eight with double bridges and two with triple bridges). Bridges were most often found over the anterior interventricular artery (35 hearts). Bridges were also found over the diagonal branch of the left coronary artery (14), over the left marginal branch (five) and over the inferior interventricular branch of the left coronary artery (six). Bridges were also found over the right coronary artery (15 hearts), over the right marginal branch (four) and over the inferior interventricular branch of the right coronary artery (two). The presence of bridges appeared to be related to coronary dominance, especially in the left coronary circulation. Forty-six (66.6%) of the hearts with bridges were left dominant. Forty-two of these had bridges over the left coronary circulation and four over the right coronary circulation. Seventeen hearts (24.6%) were right dominant. Eleven of these had bridges over the right coronary circulation and six over the left coronary circulation. The remaining six hearts were co-dominant with four having bridges over the left coronary circulation and two over the right coronary circulation. The mean length of the bridges was 31 mm and the mean depth was 12 mm. The possible clinical implications of myocardial bridging may vary from protection against atherosclerosis to systolic vessel compression and resultant myocardial ischaemia.