Technical considerations in aortocoronary bypass grafting

Since the inception of aortocoronary bypass surgery, many technical advances have been rapidly achieved. Early experience was limited to reversed saphenous vein grafting of single vessel coronary artery disease. Multiple grafts to several vessels soon became commonplace and sequential grafting techniques were developed. Expanded use of the internal mammary artery resulted after analysis of superior patency rates achieved with this conduit. Use of alternative conduits such as upper extremity veins, allogenic veins, synthetic graft material (polytetrafluorethylene), radial artery, splenic artery, and gastroepiploic artery have been explored. Apart from the gastroepiploic vessel, none of these alternative conduits have been suitable. A grat deal of effort has been directed at the mechanisms of saphenous vein occlusion including technical considerations, early thrombosis, intimal hyperplasia and graft atherosclerosis. Platelet inhibition and lipid reduction have shown promise in improving patency rates. Further work in these areas should lead to even better results.     

Evaluation of iloprost to prevent vasospasm in coronary artery bypass grafts

This study assessed the efficacy of iloprost in relieving vasospasm in coronary artery bypass grafts. Radial artery (RA), left internal thoracic artery (LITA) and saphenous vein (SV) grafts were taken from 20 patients (13 men and seven women, mean age 63.8 years [range 48-74 years]) scheduled to undergo coronary artery bypass grafting. Ten 3 mm vascular rings were cut from each graft and kept under tension for at least 60 min. They were kept alive with 37 degrees C oxygenated Krebs solution. Smooth muscle contraction was achieved with phenylephrine before iloprost was administered every 2 min, starting at a concentration of 10(-9) mol/l and increasing in logarithmic increments to a concentration of 10(-5) mol/l. The vasodilation response to iloprost started in all samples at a concentration of 10(-9) mol/l and increased with each incremental increase in iloprost concentration up to 10(-5) mol/l. These data suggest that local administration of iloprost has a role in relieving graft vasospasm during harvesting and preparation for coronary artery bypass grafting.     

THE LIMA SUCCESS STORY — WHITHER OTHER ARTERIAL GRAFTS — ARE VEIN GRAFTS OBSOLETE ?

SUMMARY The long-term benefit of myocardial revascularisation depends largely upon the continued patency of bypass grafts, but the long-term patency of vein grafts is poor. To improve the results of myocardial revascularisation, either measures to increase the patency of saphenous vein grafts or alternative conduits are required. Use of the left internal mammary artery as a graft is known to increase survival, and this has prompted wider use of other arterial grafts in the expectation that they will further enhance the long-term results of coronary artery bypass. This policy is based upon sound theory, but convincing evidence that it improves survival is lacking. Meanwhile, advances in the understanding of the pathology of vein graft occlusion have given rise to new methods of increasing vein graft patency. While these techniques are, as yet, only experimental, if translated into clinical practice, the places of arterial and venous grafts may require further assessment.     

Intraoperative assessment of coronary grafts by novel digital epivascular imaging.

OBJECTIVE: We sought to validate and evaluate 2 novel intraoperative ultrasound probes for epicoronary and epiaortic imaging. BACKGROUND: The noninvasive intraoperative assessment of successful coronary artery bypass grafting remains a challenge. METHODS: A total of 19 consecutive patients (4 female, 15 male; mean age 60.5 +/- 13.8 years SD, range 34-84) underwent coronary artery bypass grafting. The epivascular probes (GE Ultrasound) were validated in vitro and intraoperatively. Coronary arteries, grafts, and ascending aorta were imaged and quantified. RESULTS: Mean adjusted flow measured by flowmeter was 3.25 L, SE 0.47 (range: 1-5.5 L) and was 3.15 L, SE 0.46 (range: 1-5.0 L) by ultrasound, with r = 0.97, P <.0001. Intraoperatively, 56 native coronary vessels were bypassed using 15 left internal mammary artery grafts, 25 vein grafts, and 16 venous jump grafts. A total of 15 left internal mammary artery grafts (100%), 12 left internal mammary artery anastomoses (80%), 20 vein grafts (15 left anterior descending coronary arteries, left circumflex artery grafts, 5 right coronary artery grafts) (80%), 4 jump grafts (25%), and 15 ascending aortas (78%) were successfully imaged by inexperienced surgeons. Doppler flow measurements were possible in 50 vessels (89%). Mean lumen diameter for graft arteries (veins) was 2 mm (2.87 mm), maximal velocity was 72 cm/s (46 cm/s), and mean velocity was 29 cm/s (21 cm/s) with a mean flow rate of 70 mL/m (55 mL/m). CONCLUSIONS: We conclude that: (1) the novel intraoperative probes measure validated flow; (2) intraoperative hemodynamic assessment of graft patency is feasible without a learning curve; and (3) these findings should encourage the routine use of these intraoperative epivascular digital ultrasound probes.     

Repeat myocardial revascularization for uncontrollable angina after occlusion of prior aortocoronary bypass.

Twelve patients at Emory University Hospital have had repeat myocardial revascularization for recurrent, uncontrollable, disabling angina pectoris after previous coronary artery bypass grafts. The interval betweeen initial bypass procedure and reoperation ranged from six weeks to six years. The native coronary circulation remained unchanged in six, had developed additional proximal (left main) obstruction in four, and had advanced stenosis at the site of former anastomosis in three. Repeat revascularization consisted of new vein graft construction in eight and vein and internal mammary artery graft in four, with an average of 1.9 grafts per patient. There were no deaths. Seven of 12 patients (60%) are now asymptomatic and three of 12 (25%) are significantly improved. Patency of new grafts studied by elective repeat coronary angiography in six patients showed patency of all grafts to the left anterior descending artery and four of six grafts to other vessels. Analysis of the initial graft closures, method for selecting patients to undergo a second procedure, and operative technics believed important in safety of reoperation and avoidance of repeat early graft occlusion are presented.     

64层螺旋CT在评价冠状动脉桥血管中的价值

目的探讨64层螺旋CT在诊断冠状动脉桥血管的临床价值。方法对21例冠状动脉搭桥术的患者行64层螺旋CT心、胸部血管造影检查。对所有扫描原始数据行冠状、矢状MPR、曲面重建(CPR)以及VR、MIP重建。由两位有经验的放射科医生对所有图像进行观察,对桥血管狭窄进行诊断,并评价其狭窄程度。8例CT诊断桥血管重度狭窄(管腔狭窄>75%)或闭塞的患者同时行选择性血管造影检查。结果21例患者均可清晰地显示冠状动脉各主要分支,并能清晰地显示其斑块和管腔的狭窄。21例患者经螺旋CT心、胸部血管造影检查,可清晰显示52条桥血管,其中13条桥血管出现再狭窄(10条为大隐静脉桥血管,3条为乳内动脉桥血管),狭窄部位均位于桥血管吻合口处;重度狭窄7条,闭塞1条,此8条桥血管均与选择性血管的结果相吻合,CT评价冠状动脉桥血管重度狭窄的准确性为100%。结论64层螺旋CT心、胸血管造影检查不但能显示冠状动脉桥血管,而且能清晰地显示原始的冠状动脉及冠状动脉与桥血管的吻合口,是评价冠状动脉桥血管的一种有效的可靠的检查方法。     

Reoperative off-pump coronary artery bypass grafting: current outcomes,concerns and controversies

Increasing numbers of patients have undergone coronary artery bypass grafting in the last four decades. As a result, the incidence of reoperative coronary artery bypass grafting is rising. Reoperative procedures pose several technical difficulties and are associated with increased operative risks, which exceed those of the initial revascularization. As the incidence of reoperative procedures is increasing so is the experience of reoperative coronary artery bypass grafting, with the resultant evolution of several alternative strategies to lower the operative risks. These strategies include alternative techniques for re-entry, strict avoidance of graft manipulation to minimize the risk of graft atheroembolism, and modification of the method of myocardial protection, depending on the status of the native coronary circulation and the patency of venous or arterial grafts. Off-pump coronary artery bypass grafting is one such technique that, through the avoidance of inherent risks of cardiopulmonary bypass, has the potential to reduce the morbidity associated with reoperative coronary artery bypass grafting. This article evaluates the current outcomes of reoperative off-pump coronary artery bypass grafting, and highlights the concerns and controversies associated with this strategy.     

The statistical analysis of graft patency data in a clinical trial of antiplatelet agents following coronary artery bypass grafting

Because most coronary artery bypass patients receive more than one graft at surgery, it is most important to determine whether statistical analysis of graft patency should be performed on the premise that the multiple grafts within patients are dependent or independent experimental units. Veterans Administration Cooperative Study No. 207 was a multicenter clinical trial comparing four different antiplatelet regimens to placebo in the prevention of graft occlusion following coronary artery bypass grafting. Using the results from the 1-week postoperative angiograms from the Veterans Administration Cooperative Study No. 207, in which there were 3.2 distal anastomoses per patient, we have tested the hypothesis that grafts within patients tend to act dependently with respect to patency or occlusion by comparing the graft patency data to a binomial distribution (i.e., that distribution that would have been manifest if grafts were independent). Because the graft patency results in Study No. 207 significantly deviated from the binomial distribution (p = 0.0003), a more appropriate analysis for graft patency data was applied using a ratio estimate as applied to cluster sampling. The statistical methods used in 11 previous clinical trials of antithrombotic therapy after coronary artery bypass grafting were examined. Only one of the previous studies used such an analysis, and three additional reports attempted to correct for dependency of grafts within patients in their analyses using other statistical methods. In seven of the studies the investigators did not address the potential problem of a dependent relationship between multiple grafts within patients. We conclude that grafts within patients act as dependent experimental units and that the ratio estimate as applied to cluster sampling may be appropriately applied to these data.     

What has happened to multiple arterial grafting in coronary artery bypass grafting surgery?

Coronary artery bypass grafting (CABG) is a well-established therapy for patients with multivessel coronary artery disease, with excellent short- and medium-term results. This is best illustrated by studies comparing percutaneous coronary interventions (PCIs) with CABG surgery, where CABG continues to offer better event-free survival. However, there has been increasing concern about the long-term patency of vein grafts utilized for CABG when compared with arterial grafts. Some have suggested that revascularization with arterial grafts rather than vein grafts may result in improved outcomes following CABG. This is particularly important when one considers that graft occlusion can result in recurrence of disabling angina, rehospitalization, reintervention and death. To date, however, multiple arterial grafts have yet to become the standard approach for patients undergoing CABG. This is best exemplified by reports from large registries suggesting that the use of multiple arterial grafting is limited to approximately 10% of all patients undergoing CABG. In this article, we will provide some of the evidence outlining the risk and benefits of multiple arterial grafting, but more importantly, begin to explore why the utilization of multiple arterial grafting does not appear to be increasing significantly.     

Assessment of coronary artery bypass graft patency by multidetector computed tomography and electron-beam tomography

This case report describes the use of retrospectively ECG-gated 16-slice multidetector computed tomography (MDCT) and electron-beam tomography (EBT) for assessing bypass graft patency in two patients with recurrent angina after coronary artery bypass graft surgery. The results of each tomographic modality were compared to the findings of traditional coronary angiography. In the first patient MDCT showed occlusion of the left internal mammary artery (LIMA) and saphenous vein graft after the second anastomosis. Coronary angiography confirmed these findings. In the second patient EBT showed patency of the LIMA and saphenous vein graft. After the first anastomosis of the saphenous vein graft, the connected vessel filled poorly. Coronary angiography confirmed both grafts to be patent, and detected an occlusion distal to the first anastomosis. These findings support the evidence that both MDCT and EBT are suitable techniques for establishing bypass graft patency by non-invasive means.     

Composite arterial grafting

The success of coronary artery bypass grafting, the gold standard for the treatment of multivessel coronary artery disease, is limited by poor long-term vein-graft patency. By contrast, the left internal mammary artery has been demonstrated to have a superior graft patency rate and has provided excellent clinical results. This suggests that the use of arterial conduits for coronary artery bypass grafting may be beneficial for long-term results. Recently, there has been an upsurge in the use of arterial grafts for myocardial revascularization based on the clinical advantage of the use of the left internal mammary artery as a bypass conduit. Many retrospective studies have supported the safety and the effectiveness of arterial grafting, and it has become apparent that the free arterial graft can be used as a branched or a lengthened conduit to the in situ arterial graft by adopting one or more of the several composite grafting techniques. Arterial composite grafts with or without sequential grafting techniques appear an attractive strategy as increased number of distal coronary anastomoses can be performed, with a limited number of grafts, avoiding proximal aortic anastomoses. However, concerns regarding the total dependence of the coronary bypass flow on the flow of one in situ arterial graft and technical error, resulting in compromised flow in one or both limbs of the composite graft have prevented composite arterial grafting from being universally adopted. It is expected that in the near future a prospective, multi-institutional, randomized controlled trial, to compare the short- and long-term outcomes of exclusive arterial grafting using composite and conventional aortocoronary revascularization strategies, will be undertaken to validate the safety and efficacy of composite arterial grafting.     

Off-pump strategy in high-risk coronary artery bypass reoperations

OBJECTIVE: To determine the role of off-pump coronary artery bypass grafting in the treatment of patients with severe recurrent angina after coronary artery bypass grafting who are not suitable for percutaneous coronary intervention and are considered too high risk for conventional on-pump revascularization. PATIENTS AND METHODS: All patients who needed single- or double-vessel revascularization at reoperation with a predicted operative mortality of 10% or higher between March 4, 1994, and December 31, 2002, were studied. Risk stratification was performed using both the Parsonnet risk scoring system and the European System for Cardiac Operative Risk Evaluation. Active follow-up by questionnaire investigated major adverse cardiac events. RESULTS: This study consisted of 84 patients with a median age of 69 years (interquartile range, 62-75 years); 14 (17%) were female. All patients had class III/IV symptoms. Previous operations included multiple coronary artery bypass grafts (15 patients [18%]) and heart transplantation (1 patient [1%]). Internal thoracic artery graft from a previous operation was patent in 43 patients (51%). Perioperative hemodynamic support with inotropes (35%) and intra-aortic balloon pump (14%) or ventricular assist device (2%) was common. The surgical approach varied for each patient. One operative death (1%) occurred. Estimated survival at 5 and 7 years was 77% and 67%, respectively. Late major adverse cardiac events observed during follow-up were cardiac death (n=66), nonoperative reintervention (n=8), and nonfatal myocardial infarction (n=5). CONCLUSION: Off-pump coronary artery bypass grafting can mitigate reoperative risk in patients with an estimated risk of 10% or higher who are undergoing single- or double-vessel revascularization with satisfactory long-term outcome.     

升主动脉No—touch技术在冠心病手术中的应用

目的探讨和评价升主动脉不接触技术（No—touch）在冠状动脉旁路移植手术中的应用。方法回顾5例合并升主动脉粥样硬化冠心病患者的临床资料,男3例,女2例,年龄68--76岁,平均70．2岁。5例均采用常规胸骨正中切口行非体外循环下冠脉搭桥（OPCABG）。2例行双侧乳内动脉原位移植,3例以左乳内动脉为唯一的供血来源,大隐静脉近端与左乳内动脉端侧吻合。所有患者未在升主动脉上进行任何操作。结果5例患者共移植血管13支,全组手术均顺利完成,痊愈出院,无院内死亡。手术后所有忠者心绞痛均消失,心功能改善I～II级。无围术期心肌梗死和神经系统并发症发生。结论对合并升主动脉粥样硬化的冠心病患者,采用OPCABG结合升主动脉不接触（No—touch）技术,可使病变冠脉完全再血管化,降低术后脑卒中的发生率,临床效果满意。     

Early recognition of regional cardiac ischemia using a 3-axis accelerometer sensor

Perioperative mortality in coronary artery bypass grafting is usually caused by reduced left ventricular function due to regional myocardial ischemia or infarction. Post-operative graft occlusion is a well-known problem in coronary surgery. A sensitive tool to detect graft occlusion and monitor myocardial function may give the opportunity to revise malfunctioning grafts before departure from the hospital. This paper describes how a new method can detect cardiac ischemia using a 3-axis piezoelectric accelerometer. In three anesthetized pigs, a 3-axis piezoelectric accelerometer was sutured on the lateral free wall of the left ventricle. The left anterior descending (LAD) was occluded for different time periods and the accelerometer data were sampled with a PC. Short-time Fourier transform was calculated based on the accelerometer time series. The results were visualized using a 2D color-coded time-frequency plot. In the area of occlusion, a change to stronger power of higher harmonics was observed. Consequently, a difference value between the instant frequency pattern and a reference frequency pattern showed a rise in absolute value during the occlusion period. The preliminary results indicate that early recognition of regional cardiac ischemia is possible by analyzing accelerometer data acquired from the three animal trials using the prototype 3-axis accelerometer sensor.     

Qualitative angiographic and quantitative myocardial perfusion assessment using fluorescent cardiac imaging during graded coronary artery bypass stenosis

Intraoperative graft assessment in coronary artery bypass (CAB) grafting is important to avoid early graft failure. This study aimed to evaluate the accuracy of fluorescent cardiac imaging (FCI) for intraoperative qualitative angiographic and quantitative myocardial perfusion assessment during graded CAB stenosis compared to coronary angiography (CA). After CAB grafting to the left anterior descending coronary artery, graded distal bypass stenoses were created in ten pigs by 25, 50, 75, and 100% flow reduction assessed by transit-time flow measurement (TTFM). Visual angiographic assessment was performed by FCI and CA during baseline and graded bypass stenoses. Altered myocardial perfusion was assessed by quantitative intraoperative fluorescence intensity (QIFI) derived from FCI and correlated to TTFM. Patent bypass grafts and graft occlusion were visualized successfully by FCI and CA, while discrimination between various graded bypass stenosis was possible in 73.3%. The degree of CAB stenosis was overestimated in 16.7% and underestimated in 10.0% by FCI compared to CA. Graded CAB stenosis reduced regional myocardial perfusion quantified by decreased QIFI value (p?<?0.001). Mean QIFI value was 76.8 (95% CI 67.2–86.3) during baseline, 55.6 (95% CI 45.3–65.9) during 25% flow-reduction, 30.6 (95% CI 22.3–39.0) during 50% flow-reduction, 20.3 (95% CI 15.4–25.3) during 75% flow-reduction, and 0 during CAB occlusion (p?<?0.001) with a significant correlation to TTFM (r?=?0.955; p?<?0.0001). Solely visual assessment of CAB quality using FCI is limited as compared to CA. Additional QIFI assessment identified graded CAB stenosis and occlusion with a significant correlation to TTFM.     

Use of the internal mammary artery for myocardial revascularization in a patient with radiation-induced coronary artery disease.

A 9-year-old boy with clinical stage IIA Hodgkin's disease underwent radiotherapy to the neck and mediastinum. Twenty-two years later, he sought medical attention because of angina pectoris. Cardiac catheterization revealed proximally located high-grade stenoses of the left main, left anterior descending, circumflex, and right coronary arteries. He underwent coronary artery bypass grafting with use of the left internal mammary artery to the left anterior descending coronary artery and reversed saphenous vein grafts to the circumflex and right coronary arteries. The postoperative course was uncomplicated. Previous radiotherapy to the mediastinum should be considered a risk factor for the development of premature coronary artery disease. Surgical revascularization is the preferred method of management. A combination of an internal mammary artery graft and a saphenous vein graft should be used in young patients.     

Prevention of coronary in-stent restenosis and vein graft failure: Does vascular gene therapy have a role?

Coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI), including stent insertion, are established therapies in both acute coronary syndromes (ACS) and symptomatic chronic coronary artery disease refractory to pharmacological therapy. These continually advancing treatments remain limited by failure of conduit grafts in CABG and by restenosis or thrombosis of stented vessel segments in PCI caused by neointimal hyperplasia, impaired endothelialisation and accelerated atherosclerosis. While pharmacological and technological advancements have improved patient outcomes following both procedures, when grafts or stents fail these result in significant health burdens. In this review we discuss the pathophysiology of vein graft disease and in-stent restenosis, gene therapy vector development and design, and translation from pre-clinical animal models through human clinical trials. We identify the key issues that are currently preventing vascular gene therapy from interfacing with clinical use and introduce the areas of research attempting to overcome these.     

Myocardial infarction following coronary artery bypass graft surgery increases healthcare resource utilization

OBJECTIVE: To assess the health economic impact of perioperative myocardial infarction in a cohort of patients undergoing coronary artery bypass graft surgery. DESIGN: Retrospective cohort analysis using data from hospital bills and uniform billing forms. SETTING: A total of 147 geographically diverse hospitals in the United States. PATIENTS: The study population consisted of 2,102 coronary artery bypass graft surgery patients enrolled in the PRIMO-CABG trial at U.S. sites between January 2002 and February 2003. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Resource utilization and costs during the index hospitalization and during a 6-month follow-up period were compared between patients who had a myocardial infarction by postoperative day 4 and those who did not. Linear regression was used to examine whether myocardial infarction by day 4 was associated with index hospitalization costs, after adjusting for baseline characteristics. Myocardial infarction occurred in 191 (9.1%) patients undergoing coronary artery bypass graft surgery. Myocardial infarction was associated with a doubling of intensive care unit time (3.5 days among patients with no myocardial infarction and 7.1 days among patients with myocardial infarction, p < .01) and a 48% increase in hospital length of stay. Myocardial infarction by day 4 was associated with a 43% increase in hospital costs, a 29% increase in physician service costs, a 41% increase in total costs during the index hospitalization, and a 38% increase in cumulative 6-month costs. After baseline adjustment, myocardial infarction continued to be associated with higher index hospitalization costs. CONCLUSIONS: Myocardial infarction following coronary artery bypass graft surgery was associated with a significant increase in intensive care unit time, hospital length of stay, and overall costs, which contributed to greater hospital and physician service costs. Healthcare resource utilization is increased in patients sustaining a myocardial infarction following coronary artery bypass graft surgery.     

Carotid-subclavian bypass in occlusive disease of subclavian artery: more important today than before

After left internal mammary artery graft is anastomosed to the coronary artery, atherosclerotic occlusion of subclavian artery becomes more important, because the vascular segment between the origin of the subclavian artery and the coronary artery becomes a part of the coronary circulation functionally. The subclavian artery occlusion may be treated through percutaneous intervention including balloon angioplasty alone or with stent. But failure of initial treatment by percutaneous intervention is possible especially in some proximal and total occlusions. In those cases, surgical options include extra anatomic reconstruction, anatomic reconstruction with transthoracic approach or redo-coronary artery surgery in patients with coronary steal syndrome. In this retrospective study, the medical records of 66 patients underwent carotid-subclavian bypass under general or local anesthesia between January, 1990 and January, 2003 were reviewed to analyze the early and long-term results of carotid-subclavian bypass with polytetrafluoroethylene grafts. There were no intraoperative mortalities. There were only one peroperative cerebrovascular accident and one death due to myocardial ischemia early in the post-operative period. Over a mean follow up of 96 months (6 month-144 months), thirteen patients died due to various reasons and there were eleven late graft thrombosis. The primary patency rates at 1, 3, 5 and 10 years were 98%, 91%, 83% and 47%, and the overall survival rates at 1, 3, 5 and 10 years were 100%, 95%, 93% and 38%, respectively. Carotid-subclavian bypass with polytetrafluoroethylene grafts is a safe, effective and durable procedure. It can be easily applied even under regional anesthesia when percutaneous intervention is unsuccessful or impossible.     

体外循环心脏不停跳技术在低射血分数患者冠状动脉旁路移植术中的应用

目的：总结体外循环心脏不停跳冠状动脉旁路移植术治疗心功能严重低下的冠心病患者的经验。方法：2005年9月-2007年9月共有37例射血分数（EF）〈30％的高危冠心病患者采用体外循环心脏不停跳冠状动脉旁路移植术,其中男性31例,女性6例;年龄27—76（平均61．6±7．8）岁。冠脉造影提示双支病变2例,多支病变35例,左主干病变10例。术前射血分数0．18～0．29（平均0．24±0．031）。合并心肌梗死史22例,支架植入治疗史6例。纽约心脏病协会（NYHA）心功能Ⅱ级11例,Ⅲ级23例,Ⅳ级3例。合并轻、中度二尖瓣返流11例,合并室壁瘤5例,左室血栓2例。超声心动图检查提示左心室舒张末期内径53～76mm,平均（61．3±4．2）mm。结果：平均体外循环时间（41±15）min,平均远端吻合口（3．7±1．1）个,使用主动脉内球囊反搏3例,均在手术中安放。住院治疗期间病死2例,脑梗死导致左侧肢体偏瘫1例,肺梗死1例。在出院后随访2—21个月中,有3例病死。3例慢性心衰需长期药物治疗。其余患者心功能良好。结论：体外循环心脏不停跳冠状动脉旁路移植手术能避免低射血分数冠心病患者术中的缺血损害,治疗结果满意。