Progression from stenosis to occlusion in the proximal native coronary artery after coronary artery bypass grafting

Coronary artery bypass grafting (CABG) is an established treatment for multivessel coronary artery disease. However, problematic situations are occasionally encountered after CABG, such as disease progression in the native coronary artery with graft occlusion, which causes difficulty in revascularization. The purpose of this study was to evaluate changes in the native coronary artery after CABG. Between 2009 and 2012 in our institution, 351 patients underwent CABG, and 768 bypass grafts were anastomosed to non-occluded coronary arteries. Of these, 489 bypass grafts had available early postoperative angiographic results (≤6 months) suitable for assessment in this study. We defined malignant graft failure after CABG to be bypass graft occlusion and de novo complete occlusion of the target native coronary artery proximal to the graft anastomosis site. In the early angiographic results, 17 grafts were occluded (17/489; 3.5 %). Two of the grafts displayed malignant graft failure (a saphenous vein graft to the right coronary artery and a saphenous vein graft to the diagonal branch) (2 of 17 occluded grafts, and 2 of 489 studied grafts). Of the patent bypass grafts, 24 involved progression to occlusion in the proximal native coronary artery (19 saphenous vein grafts, 4 left internal thoracic artery grafts, and 1 right internal thoracic artery graft). Malignant graft failure was uncommon during short-term follow-up after CABG. At the same time, disease progression in the proximal native coronary artery from stenosis to occlusion following patent bypass grafting was relatively common, especially for vein grafts.     

Aneurysm of a saphenous vein bypass graft associated with aneurysms of native coronary arteries

Aneurysm formation in saphenous vein aortocoronary bypass grafts is an extremely rare complication of coronary artery bypass surgery. Aneurysms of native coronary arteries are found in a small percentage of patients at autopsy. Reported is a case with multiple coronary artery aneurysms in which a dissecting aneurysm of the saphenous vein bypass graft also developed following coronary artery bypass surgery. This is the first report of such association.     

Coronary artery bypass with bovine internal mammary artery graft

Ten of 1,025 patients undergoing coronary bypass surgery received one or two bovine internal mammary artery grafts. Surgery consisted in quadruple coronary bypass in 1 case, triple coronary bypass in 3 cases and double coronary bypass in 6 cases using 4 autologous saphenous vein grafts, 6 autologous internal mammary artery grafts and 13 bovine internal mammary artery grafts. It was necessary to use bovine internal mammary artery grafts because of total bilateral venous stripping in 5 patients, diffuse, bilateral varicose veins in 4 patients and because of the insufficient length of the vein in 1 patient. Short and medium-term (12 months) angiographic studies of the bovine grafts showed 5 occluded grafts, 2 proximal graft stenoses, and 1 patient graft up to the time of his death of extracardiac causes, with a maximum follow-up of 13 months. One of these 10 patients died in the early postoperative period of extracardiac causes with a patent bovine coronary graft. Another patient died in the 5th postoperative month during reoperation motivated by occlusion of the two implanted bovine coronary grafts. The other 8 patients are alive and stable from the coronary view point. Bovine internal mammary artery grafts may be used to manage an acute episode of coronary insufficiency by providing the time for the collateral circulation to develop but it does not provide a complete and durable method of revascularisation. Their use should therefore be reserved for exceptional cases.     

Systolic compression of bypass grafts

Myocardial bridging, systolic compression of an intramyocardial segment of an epicardial coronary artery, is well known to involve native coronary arteries. Systolic compression of bypass grafts has been rarely described. We present two cases of dynamic systolic compression of bypass grafts to native coronary arteries: one of a vein graft to the right coronary artery, and another of a left internal mammary artery to the left anterior descending artery.     

Symptomatic true aneurysm of a venous bypass with compression of the right atrium

A symptomatic true aneurysm of a saphenous vein graft to the right coronary artery in a female patient twelve years after bypass surgery is presented. Beating heart surgery included resection of the aneurysmatic saphenous vein graft, reconstruction of the right atrium and coronary artery bypass grafting to the right coronary artery. The symptoms of aneurysms of vein grafts, the diagnostic procedures and the surgical treatment are discussed.     

移植静脉外膜增生与兔血管再狭窄的相关性

目的 探讨冠状动脉旁路移植术后移植静脉外膜增生与血管再狭窄的相关性.方法 构建20例兔颈动脉旁路移植模型,术后当日行血管彩色多普勒检查,检测移植静脉的通畅性.术后30 d,取出移植静脉,组织病理标本切片、HE染色,测量外膜面积和管腔面积.用统计软件分析外膜面积与管腔面积的相关性.结果 术后当日,血管多普勒证明,所有20例模型移植静脉全部通畅.统计软件分析结果显示,移植静脉外膜面积与管腔面积成直线关系.结论 移植静脉外膜增生与血管管腔再狭窄有相关性.移植静脉外膜增生越重,管腔越狭窄.     

大隐静脉序贯桥行冠状动脉螺旋CT的中期随访结果

目的：评价冠状动脉旁路移植术中应用大隐静脉序贯桥的中期临床效果。方法: 对37例冠状动脉粥样硬化性心脏病患者以大隐静脉序贯桥行冠状动脉旁路移植术,其中男25例,女12例,年龄45-69岁,不稳定性心绞痛患者23例,陈旧性心肌梗塞患者10例,急性心肌梗塞患者4例,于术后2年行冠状动脉螺旋CT随访。结果：37例病人中,35例全部血管桥均通畅,有2例病人乳内动脉桥路通畅,大隐静脉血管桥闭塞,未予介入或手术干预。结论:大隐静脉序贯桥中期随访通畅率良好,虽有“一闭俱闭”的风险,但大多数不会导致心肌梗死。     

Saphenous vein grafts: to use or not to use?

The choice of the graft conduit is crucial to the success of coronary artery bypass grafting (CABG) because the patency of a coronary conduit is closely associated with an uneventful postoperative course and better long-term patient survival. From the beginning of coronary bypass surgery venous conduits particularly the great saphenous veins (GSV) have been the most frequently used coronary conduit from the beginning of the coronary bypass surgery. However, over the last decade or so, coronary bypass graft surgery with arterial revascularization of all diseased coronaries has shown to be efficient because arterial grafts have better long-term patency, especially left internal mammary artery (LIMA), compared with venous grafts. Early vein graft failure coupled with occlusion is the most important limitation of saphenous vein grafts. Nevertheless, vein grafting is still an integral part of cardiac surgical practice. This review provides a summary of the patency rates, technical features and certain characteristics of the venous conduits. It also examines the current understanding and knowledge of venous histology, vein graft pathology and the associated endothelial and smooth muscle cell physiology and pharmacology. In addition, the existing and the emerging strategies to combat and control vein graft intimal hyperplasia and accelerated atherosclerosis are reviewed in detail.     

The renin angiotensin system in bypass graft surgery

The renin angiotensin system is implicated in the development of vein graft disease after coronary artery bypass surgery. Components of this system have been shown to play important roles in determining the short-term and long-term performance of coronary artery bypass grafts. Significant differences exist in the commonly used arterial and venous grafts in angiotensin converting enzyme activity and angiotensin responses. The existence of a dual enzyme pathway in angiotensin II formation has also been demonstrated. Such findings have implications for the use of AT1-receptor antagonists over enzyme inhibitors to improve graft performance and prevent the development of coronary artery bypass graft disease.     

The acute and chronic effects of G-lasing on femoral vein grafts in dogs

Each year, 5% of all coronary artery bypass operations are repeat procedures, and 15%-30% of coronary artery vein grafts occlude within the first eighteen months postoperatively. To evaluate the macroscopic and histologic effects of G-lasing on vein grafts and their patency, femoral veins were used to bypass bilaterally induced stenoses of femoral arteries in 10 dogs. The left vein grafts were G-lased with a 1.5 mm, hot-tipped argon laser at 5 watts for ninety seconds, while the right grafts were used as the controls. Acutely, each vein graft demonstrated no evidence of charring or perforation. The percentage of endothelium present in the G-lased vein grafts was consistently less than 5%, whereas the control vein grafts had an average of 70%. After ten weeks, the animals were sacrificed, and the vein grafts were evaluated for histologic changes and patency. There were no significant microscopic differences between the G-lased and control vein grafts. A statistically significant difference in graft patency was not achieved between G-Lased and control vein grafts at 10 weeks, but only a small number of grafts were studied. Further studies will be needed to evaluate the effects of G-lasing on the long-term patency of vein grafts.     

Saphenous vein grafts: to use or not to use?

The choice of the graft conduit is crucial to the success of coronary artery bypass grafting (CABG) because the patency of a coronary conduit is closely associated with an uneventful postoperative course and better long-term patient survival. From the beginning of coronary bypass surgery venous conduits particularly the great saphenous vein (GSV) has been the most frequently used coronary conduit. However, over the last decade or so, coronary bypass graft surgery with arterial revascularization of all diseased coronaries has shown to be efficient because arterial grafts have better long-term patency, especially left internal mammary artery (LIMA), compared with venous grafts. Early vein graft failure coupled with occlusion is the most important limitation of saphenous vein grafts. Nevertheless, vein grafting is still an integral part of cardiac surgical practice. This review provides a summary of the patency rates, technical features and certain characteristics of the venous conduits. It also examines the current understanding and knowledge of venous histology, vein graft pathology and the associated endothelial and smooth muscle cell physiology and pharmacology. In addition, the existing and the emerging strategies to combat and control vein graft intimal hyperplasia and accelerated atherosclerosis are reviewed in detail.     

Internal thoracic artery grafts: 20-year clinical follow-up

Objectives. This study compared the long-term clinical results of coronary artery bypass surgery in patients with internal thoracic artery grafts with those in patients with vein grafts only.Background. Aortocoronary artery bypass surgery has been performed for >25 years, primarily utilizing the saphenous vein and internal thoracic artery as conduits. Although the internal thoracic artery has been shown to confer a clinical advantage, it is not known for how many years this benefit will continue.Methods. All consecutive patients undergoing initial coronary artery bypass surgery between 1970 and 1973 were followed for up to 20 years. Clinical evaluation included survival, late myocardial infarction, need for reoperation and recurrence of angina. Patients were analyzed in three groups: vein grafts only (214 patients); a single internal thoracic artery graft with or without associated vein grafts (490 patients); and bilateral internal thoracic artery grafts (39 patients). Use of the operating microscope was also analyzed with regard to effect on survival.Results. The internal thoracic artery graft and use of the operating microscope were independent predictors of mortality and reduced the risk of dying by a factor of 0.68 and 0.76, respectively. An internal thoracic artery graft resulted in a mean survival of 4.4 years longer than that with vein grafts alone. The internal thoracic artery graft compared with vein grafts was associated with fewer reoperations (p < 0.001), fewer late myocardial infarctions, lower associated mortality rates (p < 0.04) and less early recurrence of angina (p = 0.03).Conclusions. The internal thoracic artery graft and use of the operating microscope confer a superior clinical advantage over the saphenous vein graft throughout a 20-year follow-up period. The advantage of an internal thoracic artery graft does not decrease with time, suggesting that the choice of conduit at the initial operation is more important clinically than progression of coronary artery disease.     

Coronary atherosclerosis and the bypass grafts: twenty-year follow-up of a case

A 44-year-old man was diagnosed as having coronary artery disease (CAD) by arteriography in 1964. In the subsequent 20 years, he has undergone seven angiographic studies and four coronary bypass operations. Close scrutiny of the clinical events and the angiographic studies in this patient offers important clues to the behavior of CAD and the bypass grafts, both internal mammary artery (IMA) and saphenous vein grafts (SVGs).     

Noninvasive detection of coronary artery bypass graft patency by intravenous electron beam computed tomographic angiography

This study evaluates the usefullness of intravenous electron beam computed tomographic angiography (EBA) for the detection of coronary artery bypass graft patency in 43 patients (33 men and 10 women, mean age, 65 years) who had coronary artery bypass graft surgery. EBA was performed a few days before selective bypass graft angiography (SGA). Forty axial cross-sections of angiographic images of the heart were acquired consecutively by an electrocardiographic trigger signal at 40% of the RR interval, which corresponds to the end-systolic phase. EBA data were reconstructed as a three-dimensional shaded surface display of the heart and bypass grafts. Detectability of the patency of bypass gratis was evaluated, taking selective angiographic images of the bypass grafts as a gold standard. One hundred and nine grafts (96%) out of 114 grafts were subjected to evaluation: 37 grafts were left internal mammary artery grafts (LIMA), 7 were right internal mammary artery grafts (RIMA), 6 were gastroepiploic artery grafts (GEA), 7 were free gastroepiploic artery grafts with venous drainage (free-GEA), 7 were radial artery grafts (RAG), and 45 were saphenous vein gratis (SVG). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of EBA were 98%, 100%, 100%, 91%, and 98%, respectively. EBA sampled at the end-systolic period was determined to be useful for the detection of coronary artery bypass graft patency and occlusion.     

Postoperative evaluation of radial artery grafts for coronary artery bypass grafting by transit-time Doppler flow measurements.

Due to the histological configuration of the vessel wall, the radial artery is prone to spasm as a result of handling or harvesting. Therefore, certain degrees of arterial wall spasm are unpreventable, even with appropriate pharmacologic treatment, while using the radial artery as a bypass graft in CABG. Consequently, the radial artery is only reluctantly used compared to saphenous vein grafts in CABG. In our clinical experience, the radial artery, if harvested carefully, has proved to be an excellent bypass graft. This investigation was undertaken to study the differences in blood flow measured directly after extracorporeal circulation in radial artery grafts and venous grafts. Both grafts were compared to the left internal mammarian artery anastomosed to the LAD. METHODS: Between January 1998 and December 1999, 198 patients who were undergoing coronary artery revascularization with two grafts were retrospectively investigated. In all patients, the left internal mammarian artery (LIMA) was anastomosed to the left anterior descending branch (LAD). For the second graft, either the saphenous vein or the radial artery was used. Proximal anstomoses were performed as end-to-side into the ascending aorta. Patients were divided into four groups: Group 1: n = 79 IMA-LAD, vein to the circumflex artery; Group 2: n = 56 IMA-LAD, vein to the right coronary artery; Group 3: n = 34; IMA-LAD, radial artery to the circumflex artery; Group 4: n = 29 IMA-LAD, radial artery to the right coronary artery. Graft-flow measurements were performed using the transit-time method after extracorporeal circulation was terminated. The mean systolic, diastolic, and mean blood flow were measured, and the pulsatility index was calculated. Statistical analysis was performed using the of t-test analysis between the variables mean blood flow and pulsatility index. A p-value of < 0.05 was defined as statistically significant. RESULTS: There were no statistically significant differences in mean blood flow or pulsatility index between radial artery and saphenous vein grafts to the right coronary artery and the circumflex artery, respectively. Also, there were no differences regarding vein grafts to the right coronary artery and to the circumflex artery, or regarding radial artery grafts to the two coronaries, respectively. In group 4, significantly lower blood flow to the LAD was found compared to group 1, and a significantly higher pulsatility index compared to groups 2 and 3. CONCLUSIONS: Radial artery grafts compared to saphenous vein grafts do not show significant differences early after operation in mean blood flow or pulsatility index. Further studies are needed to evaluate long-term performance of radial arteries as coronary bypass grafts and to compare the radial artery to the right mammarian artery and the standard saphenous vein graft.     

Vascular biology of coronary bypass grafts. Literature review

Myocardial revascularisation by coronary bypass surgery is the treatment of choice for patients with multivessel disease. The most commonly used grafts are the internal mammary artery and the saphenous vein. Although the use of internal mammery artery grafts gives excellent results, venous grafts, with time, are subject to atheroma which affects their patency. Improved physiopathological understanding of the natural history of grafts, especially the saphenous vein grafts, has opened the field for different operative strategies to try and reduce the incidence of coronary graft disease. This paper reviews the literature concerning the biology of coronary grafts used for myocardial revascularisation and the current and future therapeutic implications of this data.     

Measures to increase the number of mammary artery coronary artery anastomoses

Patients with single internal mammary artery (IMA) grafts along with saphenous vein grafts have been found to have fewer coronary events and longer survival after operation. To reduce bypass graft failure from intimal hyperplasia and atherosclerosis, as well as to improve results, three or more IMA grafts were placed in 215 patients from October 1982 through May 1985. Careful planning helped in bypassing the maximum number of coronary artery obstructions with arterial conduits. By using bilateral IMA grafts, sequential, and Y grafts, the number of IMA coronary artery anastomoses increases and the need for saphenous vein grafts decreases. Meticulous dissection and preparation of the entire IMA and proper construction of the anastomosis are essentials for these procedures to be successful. Two of the 215 patients died early and four died late. Ninety-five percent of the postoperative stress tests were negative and 92% of the 39 IMA grafts visualized in 13 patients studied postoperatively were patent. We found this to be a safe, challenging procedure that improved late bypass conduit success and prolonged survival.     

双源CT评价冠状动脉搭桥术后桥血管通畅率的临床研究

目的比较非体外循环下冠状动脉旁路移植术（OPCABG）与常规冠状动脉旁路移植术（常规CABG）术后5年血管桥的通畅率。方法2006年1月至2008年1月间40例单独行冠状动脉旁路移植术（CABG）的患者资料回顾性地被分为OPCABG组和常规CABG组。OPCABG组通过胸骨正中切口,在非体外循环心脏不停跳下完成CABG;常规CABG组建立常规体外循环心脏停搏下完成CABG。两组术前的一般情况无明显差异。利用双源CT造影检查及CT图像后处理,研究两种术式各条血管桥的通畅情况。结果常规CABG组及OPCABG组左乳内动脉（uMA）到前降支（LAD）的通畅率都达到100％,静脉桥的通畅率分别为93．87％和94．23％,组间比较差异均无统计学意义。结论OPCABG旁路血管桥的3~5年通畅率可以和常规CABG相媲美。OPCAB治疗冠心病的初期结果显示可以减少术后并发症,减少患者术后呼吸机辅助时间、ICU留观时间和住院时间,降低住院费用。     

High stress regions in saphenous vein bypass graft atherosclerotic lesions

Objectives. Our aim was to test the hypothesis that maximal stresses in saphenous vein atherosclerotic stenoses are greater than those in native coronary artery stenoses.Background. The patency of coronary artery saphenous vein bypass grafts decreases with time, usually because of thrombosis. Plaque rupture has been described as one mechanism of vein graft thrombosis.Methods. Twenty-six nonruptured human lesions were studied. Fourteen lesions were from native coronary arteries, and 12 were from saphenous vein bypass grafts placed a mean ± SD of 9.8 ± 3.3 years before pathologic study. The finite element method was used to determine the distribution of stress in the lesion, using estimates of material properties from previous measurements of human tissues.Results. Maximal circumferential stresses were significantly higher in the saphenous vein lesions (median 352 kPa [interquartile range 161 to 475]) than in the coronary artery lesions (median 104 kPa [interquartile range 75 to 185]) (p = 0.05). Thin-walled cylinder formulations predict that stresses are proportional to the radius of the vessel and inversely proportional to the minimal wall thickness. In this study, there was a good correlation between the maximal stress in the 26 lesions and the ratio of the square root of lumen area to minimal fibrous cap thickness (r = 0.83, p < 0.001).Conclusions. Maximal circumferential tensile stresses in saphenous vein bypass graft stenoses are higher than in native coronary artery atherosclerotic stenoses. These data suggest that strategies that decrease stresses in bypass graft atherosclerotic lesions, such as prevention of lipid accumulation, could reduce the probability of plaque rupture in bypass grafts.     

Evaluation of flow reserve in internal mammary artery in situ bypass

The internal mammary artery, when used as a conduit for coronary artery bypass, offers a better long-term patency and survival rate than the saphenous vein. However, concern exists that the flow through the internal mammary artery may be inadequate during periods of peak myocardial demand. This flow was investigated in 18 consecutive patients who were selected for coronary bypass of the left anterior descending artery using the internal mammary artery. All patients were evaluated post-operatively within 12 months by means of graded maximal stress test, cardiac catheterization and exercise thallium-201 scintigraphy. Significant improvement in work capacity, maximal rate-pressure product, effort angina and ECG abnormalities during exercise stress testing were observed following internal mammary artery myocardial revascularization. The patency rate for internal mammary artery grafts was 100% (vs 85% for vein grafts); during the followup period, occlusion of a saphenous vein bypass or development of a new stenosis in a native coronary artery was noted in five patients, and two patients were classified as having partial revascularization. Ischemia, demonstrated by perfusion deficits at peak stress which disappeared in the 3-hour delayed film, was documented in 7.4% (4/54) of the areas supplied by internal mammary artery grafts, compared to 31% (13/42) of the regions revascularized using saphenous vein conduits. Although this result was not statistically significant, a definite trend is suggested. We conclude that ischemia demonstrated by stress thallium scintigraphy in the post-operative period is uncommon when an internal mammary artery graft has been used. This suggests that adequate coronary flow exists at peak myocardial demand during exercise.