Technical Aspects of Modern Coronary Artery Bypass Surgery

Coronary surgery encompasses two thirds of all adult cardiac surgery cases. With the endless pursuit of better outcomes, modern coronary artery bypass grafting (CABG) has become technically more complex in ways that are well beyond the training of the average cardiac surgeon. The old concept of "one-technique-fits-all" has been abandoned in favour of a specialized approach tailored to the individual patient. In fact, in recent years, there is a growing movement towards establishing coronary surgery as a super-specialization of cardiac surgery.

Technical Aspects of Modern Coronary Artery Bypass Surgery aims to expand on both the basics and complexities of the technical aspects of coronary surgery. It serves as an up to date resource that illustrates and details the advancement and techniques in this field which may soon become a separate super-specialty. With a particular emphasis on illustrations, the book will be an essential reference book for both established surgeons that have no experience in advanced CABG, and the new generation of CABG surgeons.

• A complete and concise resource on all aspects of coronary surgery
• In-depth illustrative review of various coronary techniques
• Covers both current recommendations and well-established practices in the field

• Language: English
• Publisher: Academic Press
• Release date: Nov 8, 2020
• ISBN: 9780128203491

Book preview

Introduction I

Mario GaudinoDepartment of Cardiothoracic Surgery, Cornell Medicine, New York, NY, United States

Simplicity is the ultimate sophistication.

Leonardo Da Vinci

Coronary artery bypass grafting (CABG) is the most common adult cardiac surgery procedure performed globally and the foundation of our profession. CABG, however, has generally been deemed the bread-and-butter of cardiac surgery and introductory to other more complex and important cardiac surgeries.

It is just a CABG, only another CABG. This sentiment is frequently echoed in cardiac surgery operating rooms and wards, and even at academic meetings and conferences, often with some detachment or disinterest.

CABG is typically the first operation permitted to fellows in training and to junior faculty who are just commencing their practice. While mitral, aortic, and minimally invasive procedures are regarded as superspecialties requiring dedicated training and specialists, CABG is considered the operation that every surgeon should do.

As a coronary surgeon, I find this perplexing. The fact that the CABG operation is limited to the epicardial surface and that no (planned) opening of the cardiac chambers is involved may have contributed to the misperception of CABG as an easy and generalist operation. The further lack of device or prosthesis involvement may have also diminished the glamor and appeal of CABG to the surgical community.

CABG is not an easy operation and it does require considerable technical skill. The performance of an internal thoracic artery (ITA) side-to-side anastomosis on the lateral wall does not seem to me easier than the reimplantation of the aortic valve or the repair of the mitral valve with Barlow’s disease. Similarly, I find easier to deal with bleeding from the aortic root, than from an in situ right ITA-obtuse marginal artery anastomosis.

I agree that the conventional mammary-and-veins operation is highly reproducible and technically simple. I would argue, however, that this operation does not represent modern coronary surgery and should not be the standard of care for most patients (in the same way that mitral valve replacement should not be the treatment for most patients with mitral regurgitation or a Bentall operation should not be the standard for young patients with aortic root aneurysm).

CABG has evolved considerably from the time of Favaloro’s description and has become a complex procedure comprising innumerable variations that are technically challenging. It is surprising to see how many of us have been oblivious to this change.

Modern coronary surgery entails a wide spectrum of conduits, techniques, and approaches aimed at providing the best possible revascularization at the lowest risk to each patient. Mastering the technique and the strategy requires time, dedication, and humility. Modern CABG is not for cavaliers or for surgeons obsessed by the clock. If your goal is to get the case done before your colleague next door or before lunch break, I suggest that you do not lose your time reading this book.

In the following pages, a group of masters in CABG describe the details of modern coronary surgery and provide key tips and tricks for the successful performance of technically complex operations. The fact that majority of them are my good friends makes me particularly proud and happy.

Introduction II

David GlineurOttawa Heart Institute, Ottawa, ON, Canada

The pure and simple truth is rarely pure and never simple.

Oscar Wilde

Coronary artery bypass grafting has consistently represented the highest volume procedure for the vast majority of cardiac surgeons around the globe. In spite of this fact, this procedure has always been considered less interesting and simpler than operations such as mitral or aortic valve repair.

The surgical coronary artery revascularization procedure that is currently performed today was in fact devised and implemented approximately 40 years ago becoming the standard of care. The success that this procedure has had over the years comparing it with percutaneous coronary interventions has been the focus of multiple publications in recent years. It is therefore not surprising that the vast majority of surgeons still perform the operation that was created approximately 40 years ago.

It is unquestionable that percutaneous coronary intervention today has evolved quite significantly and that the superiority of the conventional (LIMA and SVG) coronary bypass compared to the latest iterations of coronary stenting has lost some ground in the past decades. A perfect example of this competition resides in the current debate about the recommendations by three major scientific societies for left main coronary artery stenting versus coronary bypass grafting. The reason for this debate stems from the fact that very few surgeons provide a competitive product that represents a true evolution from the operation devised four decades ago by the forefathers of cardiac surgery. This evolution resides not only in the selection of conduits (venous versus arterial) but also in the configuration of such conduits for particular operation as well as the platform utilized to do the operation.

As a surgeon, I understand the issues surrounding this lack of evolution in coronary artery bypass grafting as, like in many other aspects of cardiac surgery, they originate from the lack of dedication and technical preparation that would be required to perform what would actually be considered a more competitive operation against percutaneous coronary intervention. When Mario and I decided to create this book, we wanted to bring a completely different type of textbook to what most surgeons are used to; this is a book that is focused on the technical challenges, pitfalls, and recommendations that are key for any surgeon who wants adopt any of the steps (conduit selection and configuration, platform, etc.) that will make this a more competitive operation.

Chapter 1

Closing the gap between best evidence and common practice in surgical coronary revascularization: The rationale for superspecialization

John D. Puskas¹ and David P. Taggart²,³,    ¹Department of Cardiovascular Surgery, Mount Sinai Morningside, New York, NY, United States,    ²Department of Cardiovascular Surgery, University of Oxford, Oxford, United Kingdom,    ³Consultant Cardiac Surgeon, Oxford University Hospitals, Oxford, United Kingdom

Abstract

In an effort to improve the outcomes for patients with valvular heart disease, there has been a concerted push over the past decade toward the creation of Heart Valve Centers or Heart Valve Reference Centers. In 2017 the European Society of Cardiology and European Association for Cardiothoracic Surgery even jointly published a document outlining the standards that would define such a center. The same year, six North American professional organizations preeminent in the fields of Cardiac Surgery, Interventional Cardiology, Anesthesiology, and Echocardiography published a Systems of Care Document entitled A Proposal to Optimize Care for Patients with Valvular Heart Disease. These same organizations recently published an update, stating that their document was necessary because providing optimal care to patients with valvular heart disease (VHD) is an increasingly complex process, starting with early recognition and diagnosis … MDT assessment, shared decision-making, and long-term follow-up. They also note, there are an increasing number of treatment options available to patients with VHD; yet not all patients are aware of or have access to the full spectrum of interventions. The authors go on to propose an improved system of care for patients at VHD centers, whose primary goal is to optimize outcomes for all patients. They argue that the case for centers with the ability to offer more comprehensive care is logical. The authors state their intent is to set performance and quality goals for a valve center to meet benchmarks to be considered either comprehensive or primary in a manner that would be more objective than simple self-designation.

Keywords

Coronary artery bypass grafting; mitral valve; aortic valve; saphenous vein graft; arterial revascularization trial; left anterior descending; arterial grafts; specialization

Everybody is against specialization except the patient

Francis D. Moore (Surgeon Scientist) 1913–2001

In an effort to improve outcomes for patients with valvular heart disease, there has been a concerted push over the past decade toward the creation of Heart Valve Centers or Heart Valve Reference Centers. In 2017 the European Society of Cardiology and European Association for Cardiothoracic Surgery even jointly published a document outlining the standards that would define such a center [1]. The same year, six North American professional organizations preeminent in the fields of Cardiac Surgery, Interventional Cardiology, Anesthesiology and Echocardiography published a Systems of Care Document, entitled A Proposal to Optimize Care for Patients with Valvular Heart Disease. These same organizations recently published an update [2], stating that their document was necessary because providing optimal care to patients with valvular heart disease is an increasingly complex process, starting with early recognition and diagnosis … MDT assessment, shared decision-making, and long-term follow-up. They also note, there are an increasing number of treatment options available to patients with valvular heart disease; yet not all patients are aware of or have access to the full spectrum of interventions. The authors go on to propose an improved system of care for patients at valvular heart disease centers, whose primary goal is to optimize outcomes for all patients. They argue that the case for centers with the ability to offer more comprehensive care is logical. The authors state their intent is to set performance and quality goals for a valve center to meet benchmarks to be considered either comprehensive or primary in a manner that would be more objective than simple self-designation.

There are few who would argue with such sentiments, motivation, and logic. Of course, that then begs the question: why do the same statements not also apply equally well to patients with ischemic heart disease? Yet the stark reality is that no similar joint multinational or multidisciplinary proposal has ever been undertaken or even suggested for patients with ischemic heart disease. This is truly remarkable and counterintuitive, especially considering that vastly more patients in the developed world undergo procedures to treat coronary artery disease than valvular heart disease.

Although the 2014 ESC/EACTS guidelines on myocardial revascularization [3] recommend to perform [CABG] procedures in a hospital structure and by a team specialized in cardiac surgery, using written protocols (Class I, LOE B), they stop well short of recommending any special training, team, or focus on surgical coronary revascularization.

The STS Adult Cardiac Surgery Database 2019 update on outcomes and quality [4] makes clear that the majority of all adult cardiac surgical procedures performed in North America is isolated coronary artery bypass grafting (CABG) (55%), while CABG plus mitral valve (MV) or aortic valve (AV) procedures comprise an additional 8% of all procedures; thus while isolated MV or AV procedures cumulatively account for 16% of all procedures, CABG makes up 63% of all procedures recorded in the contemporary STS database.

Not only does CABG make up the large majority of all procedures performed by adult cardiac surgeons but also it continues to be performed by much the same techniques that were developed 40 years ago. Full sternotomy with aortic cannulation and clamping for cardioplegic arrest and bypass with a single internal thoracic artery graft to the left anterior descending coronary artery plus reversed saphenous vein grafts (SVGs) to all non-left anterior descending (LAD) coronary targets, remaining the most commonly performed procedure in cardiothoracic surgery. While this is an excellent and well-proven option for many patients, it does not mean that it is the best option for all patients. It ignores the fact that aortic manipulation is the single most important contributor to perioperative stroke and that SVGs have >50% rate of failure at 10 years.

For more than three decades it has been repeatedly demonstrated that arterial grafts have much superior angiographic patency rates when compared to vein grafts over the long term. Numerous authors have reported superior survival, major adverse cardiovascular events-free survival, and intervention-free survival with multiple arterial conduits compared to a single internal thoracic artery (ITA)-LAD graft plus SVGs, since the seminal report by Lytle et al. [5].

This has been shown to be true even in diabetic patients, in whom the provision of bilateral internal thoracic arteries (BITA) grafting rather than single internal thoracic artery (SITA) grafting confers a greater survival benefit than SITA grafting in nondiabetic patients [6]. Despite these compelling data, the use of bilateral ITA grafting remains less than 6% in the United States [7].

An insightful analysis of intraoperative conversion from planned BITA to SITA grafting in the arterial revascularization trial (ART) suggests that even self-selected surgeons have highly variable expertise in deploying BITA conduits, despite having performed a large number of CABG procedures in their careers. In this report the overall rate of unintentional conversion from BITA to SITA was 14% and ranged from 0% to 100% among individual surgeons and 0%–49% for individual surgical centers [8]. In the ART trial, patients who actually received more than one arterial conduit enjoyed significantly better 10 years survival and a significantly lower incidence of death/myocardial infarction/stroke than those who received a single arterial conduit [9].

Gaudino and colleagues reported a metaanalysis of pooled patient-level data from six previous prospective randomized trials comparing outcomes after CABG with LITA-LAD plus SVGs (single arterial conduit) versus LITA-LAD plus at least one radial artery graft (multiple arterial conduits). This dataset confirmed that death/myocardial infarction/repeat revascularization was less frequent when a radial artery graft was included (typically grafted to the second most important coronary target), driven by a significant reduction in graft failure among radial conduits [10]. Ten-year follow-up of these same patients has yielded similar findings with the continued divergence of these curves in favor of multiple arterial grafting [11]. Despite this and many other reports of superior graft patency and improved clinical outcomes with radial artery grafting, less than 7% of isolated CABG cases in the United States currently include a radial artery conduit [7].

The combination of BITA grafting and radial artery grafting allows total arterial revascularization (TAR), which has been shown to confer a long-term benefit in terms of symptom relief and survival [12]. Regrettably, TAR accounts for approximately 1%–2% of all multivessel CABG procedures worldwide.

The evidence that minimizing aortic manipulation can significantly reduce the incidence of stroke has been well documented over decades of practice. Most recently, Zhao and colleagues reported a network metaanalysis of 13 studies, including 37,720 patients, comparing outcomes with four alternative CABG techniques, namely, traditional on-pump CABG, off-pump CABG (OPCAB) with a partial aortic clamp for proximal anastomoses, OPCAB with a clampless facilitating device for proximal anastomoses, and OPCAB with a no-aortic-touch (an-aortic) technique in which all graft inflow was from in situ BITA conduits. They reported that an-aortic OPCAB was associated with a hazard ratio of 0.22 for stroke, 0.50 for mortality, 0.73 for myocardial infarction, compared to traditional CABG. Indeed, the relative risk of virtually every adverse event correlated with the extent of aortic manipulation in the surgical technique chosen as shown in Fig. 1.1 [13]. Perhaps due to the technical challenges that this surgical strategy entails, aortic TAR accounts for <1% of all CABG procedures worldwide.

Figure 1.1 A network metaanalysis demonstrating progressively improved clinical results with coronary bypass techniques that entail progressively less aortic manipulation [13]. (A) Stroke, (B) mortality, (C) myocardial infarction, (D) renal failure, (E) bleeding, and (F) atrial fibrillation.

Intraoperative assessment of graft patency is routine in every vascular surgical procedure except CABG. Transit-time flow measurement has been available for more than 20 years but is presently used in less than 20% of CABG cases in the United States. It has been shown to detect imperfect or failed grafts whose poor flow is otherwise not clinically apparent in the operating room [14].

So, why does the gap between best evidence and clinical practice in CABG not only persist but also that may even be widening? Why is this tolerated by cardiac surgeons and cardiologists? The answers to these questions are necessarily subjective and cannot be confirmed. There are, however, a number of plausible reasons.

First, literally all of the quality metrics for which surgeons and hospitals are held accountable are based on 30-day outcomes; it is obvious that the conventional SITA-plus-SVGs CABG approach can yield very good 30-day results in many/most patients while the benefit of the more technically challenging multiple arterial conduits will not become apparent until much later follow-up.

Second, most training programs continue to teach the conventional SITA-plus-SVGs CABG operation to virtually all trainees in a manner that has not changed meaningfully for more than three decades. Hands-on training in even relatively simple techniques such as skeletonized harvest of BITA conduits is uncommon, yet facility with skeletonized BITA harvest is, arguably, the most important stepping-stone to virtually all advanced surgical coronary revascularization. Radial artery conduits can be harvested very safely, quickly, and reliably by endoscopic techniques, but these skills are possessed by few surgical assistants and even fewer surgeons. Training in skeletonized BITA harvest and endoscopic harvest of radial arteries remains a challenge that has not been emphasized by our professional bodies and, possibly as a consequence, being imperfectly met by industry. Similarly, the adoption of OPCAB has stalled and even receded, despite the numerous potential benefits of the procedure, in part because comprehensive training in the technical nuances that make the OPCAB approach reliable and reproducible has never been made widely available or supported. Industry support for improvement in instruments to facilitate OPCAB has also stalled. Poorly trained and equipped surgeons have sometimes performed imprecise OPCAB procedures, with mixed clinical results [15], while series reported by expert OPCAB surgeons have shown excellent clinical outcomes [16–19].

The STS database reveals that there are approximately 1150 cardiac surgery programs in the United States, employing 2676 cardiac surgeons and performing 160,000 CABG operations per year. This amounts, on average, to 139 CABG cases per center per year and approximately one CABG case per surgeon per week. It is well known that there exists a volume–quality relationship for complex procedures of many types and across many industries, especially those dependent on skilled teamwork. Indeed, in other surgical fields such as orthopedics and neurosurgery superspecialization in a limited repertoire of procedures is the norm. Similarly, our own field has endorsed the need for specialists in AV and MV disease, major aortic disease, and the surgical management of heart failure; trainees expect to enter these superspecialties after completing an additional year(s) of structured training. Acknowledging the obvious fact that the margin for tolerable error in suture placement for a valvular or aortic procedure is on the order of 1–5 mm and for a coronary anastomosis is on the order of 0.1–0.5 mm brings the greater technical difficulty of coronary surgery into sharp focus. Oddly, however, it is the less technically demanding, less common procedures in our specialty that have received the greater focus on superspecialization, while surgical coronary revascularization is widely considered a commodity suitable for every cardiac surgeon to perform with no additional training. Indeed it is often dismissed as just another CABG.

It is, therefore, also possible that a major impediment to consistent excellence in CABG is that there are simply too many surgeons each performing too few CABG procedures. It is intuitive and plausible that concentrating the experience of a larger number of CABG cases in the hands of fewer cardiac surgeons and surgical teams would promote the advancement of the field. This could be the natural consequence of designating surgical coronary revascularization a superspecialty within cardiothoracic surgery. However, it may not be necessary to redistribute CABG cases in order to promote innovation and improve quality in CABG surgery. Simply adding the provision of multiple arterial grafts and avoidance of aortic manipulation to our quality metrics and providing additional remittance for intraoperative graft assessment would certainly change surgeon behavior and improve surgical coronary revascularization. Of course, formal endorsement by our professional bodies of a clinical training pathway to superspecialization in CABG, analogous to the additional training typically expected of surgeons intending to specialize in aortic surgery or transplantation/management of heart failure, would be the most effective way to systematically improve the quality of training in surgical coronary revascularization and thus the quality of CABG surgery provided to patients. While not every cardiac surgeon who performs CABG would need to complete such an additional year(s) of training, every major department should have at least one surgeon who has a committed focus on the surgical management of coronary artery disease. This must include a commitment to a comprehensive Heart Team approach, with shared decision-making, adherence to guidelines and appropriateness criteria, public reporting of outcomes, participation in research trials, and training and education [20].

Focused educational efforts dedicated to the state of the art in surgical coronary revascularization are sorely needed and should be strongly supported by all professional bodies in cardiothoracic surgery and especially cardiology. The International Coronary Congress (www.internationalcoronarycongress.com) is the only international symposium dedicated annually to identifying the best practices in CABG and promulgating them worldwide. Regrettably, textbooks in the field of cardiac surgery have typically included a single chapter for CABG, while devoting a similar amount of space to each of numerous niche procedures. The first major comprehensive textbook on state-of-the-art surgical coronary revascularization will be published this year by Oxford University Press, and the present textbook of surgical techniques in CABG published by Elsevier is another important step