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Ann Thorac Surg 2007;83:979-985
© 2007 The Society of Thoracic Surgeons
Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, Georgia
Accepted for publication October 13, 2006.
* Address correspondence to Dr Vassiliades, The Emory Clinic, Building A, 1365A Clifton Rd, NE, Suite 2100, Atlanta, GA 30322 (Email: thomas.vassiliades{at}emoryhealthcare.org).
Presented at the Fifty-second Annual Meeting of the Southern Thoracic Surgical Association, Orlando, FL, Nov 10–12, 2005.
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentDiscussionFootnotesReferences |
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Methods: Between November 1997 and March 2005, 607 consecutive patients underwent an endoACAB consisting of (1) unilateral or bilateral manual, thoracoscopic internal mammary artery (IMA) harvesting, (2) creation of a needle-directed access port in the thoracic soft tissue (non-rib-spreading), (3) cardiac positioning and stabilization using port-based instrumentation, and (4) off-pump, direct-vision, hand-sewn anastomoses to the left anterior descending (LAD), diagonal, obtuse marginal, or main right coronary arteries, or a combination. Mean follow-up time was 18.0 ± 16.0 months (range, 2.0 to 85.7 months).
Results: The IMA was used to graft the LAD in all cases. A total of 721 anastomoses were constructed using 636 conduits. Thirty-day mortality was 1.0% (6/607). A total of 379 (62.4%) had coronary angiography after operation at a mean of 18.4 ± 17.0 months. The overall patency for the LIMA to LAD was FitzGibbon A, 95.2% (324/340), and FitzGibbon A and B, 98.5% (335/340). At 5 years, event-free survival was 92% ± 2.4%.
Conclusions: The clinical outcome and angiographic patency of grafting the LAD with the LIMA off pump through a non-rib-spreading incision compares favorably with the reported data of arrested heart grafting through a median sternotomy. The endoACAB offers an excellent alternative for patients with LAD disease as a stand-alone procedure, a multivessel grafting procedure in selected patients, or as part of a hybrid procedure in conjunction with a percutaneous intervention.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesReferences |
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesReferences |
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Patient Selection
The endoACAB operation has very few contraindications beyond the initial learning curve. Patients must have a suitable LAD and left internal mammary artery (LIMA) for grafting. Morbidly obese patients [5], patients with chronic lung disease, and patients with previous thoracic and CABG procedures [6] are still considered candidates for a thoracoscopic IMA harvest, although these situations are more challenging. In addition, the presence of multivessel coronary artery disease (CAD), with few exceptions, has not been found to be an operative risk factor for the endoACAB technique [7–8]. Demographic data and baseline characteristics of all patients are listed in Table 1. Excluded were patients who required other cardiac procedures necessitating a median sternotomy or patients who had an inadequate mammary conduit as assessed by preoperative angiography.
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With the assistance of a port-based cardiac positioner (Medtronic, Minneapolis, MN; Guidant, Santa Clara, CA; Estech, Danville, CA; Computer Motion, Goleta, CA), lateral and posterolateral wall vessels can be bypassed in selected patients [10].
The protocol for heparin sodium administration consists of a full-pump dose of 400 U/kg administered before division of the IMA, with subsequent doses every 20 minutes as needed to maintain the activated clotting time at more than 400 seconds. This is fully reversed with a calculated dose of protamine sulfate after completion of the last anastomosis. Aspirin (325 mg daily) was given preoperatively and postoperatively to all patients. In addition, 75 mg of clopidogrel was administered starting 4 hours postoperatively and daily if chest drainage was less than 50 mL/h.
The target coronary arteries were occluded proximally with a silicone elastomer vessel loop (Quest Medical, Inc, Allen, TX), and retrograde bleeding was controlled with a sterile, humidified carbon dioxide blower (Medtronic DLP, Grand Rapids, MI) kept at a flow rate of 3 L/min or less. Intraluminal coronary shunts (Bio-Vascular, Inc, St. Paul, MN) were used in approximately 10% of patients when retrograde bleeding was excessive or when it was anticipated that occlusion of a coronary artery would be poorly tolerated.
Distal anastomoses were constructed with a continuous running 7-0 or 8-0-monofilament suture or interrupted nitinol microclips (Medtronic, Minneapolis, MN). Segments of reversed greater saphenous vein, radial artery, and free left or right IMA were used to construct Y grafts to the in situ IMA. These anastomoses were constructed using either a running continuous 8-0 monofilament suture or a half-continuous, half-interrupted technique.
Transit time volume flow measurements (Medistim, Medtronic) were taken 5 minutes after completion of the anastomoses and after protamine administration using flow probes 2 to 4 mm in diameter. The hemodynamic conditions of the patient were stable at the time of measurement. The following three variables were determined by analyzing the flow curve using image processing and analysis software: the pulsatility index [PI = (maximum flow – minimum flow)/mean flow]; the ratio of peak diastolic flow to peak systolic flow (pFd/pFs); and the percent diastolic time-flow integral (%DTFI) indicating the ratio of diastolic antegrade graft flow volume to the total antegrade graft flow volume.
Follow-Up
Follow-up information was collected by an in-person office visit or telephone interview ending May 2005. The interview investigated major adverse cardiac and cerebrovascular events, hospital readmissions, and coronary reinterventions. In some cases, follow-up information was obtained from the patient’s family, cardiologist, or primary care physician.
In those patients undergoing a postoperative coronary angiogram, each bypass graft was graded by the operating cardiologist on the basis of the body of the graft as well as the heel and toe of the distal anastomosis according to the scale of FitzGibbon [11]. Flow rates were graded for each graft according to the thrombolysis in myocardial infarction system [12], with special attention to flow rates in grafts scored as FitzGibbon B.
Statistical Analysis
Statistical analyses were performed by an independent group (Department of Biostatistics, Emory University School of Public Health). The data are presented as mean ± standard deviation for continuous variables or number and percentages for dichotomous variables. Univariate analysis of categoric data was done using the 
2 or Fisher exact tests. Univariate analysis of normally distributed continuous variables was done with the Student t test. Kaplan-Meier estimates were used to calculate event-free probability; Kaplan-Meier curves were compared using the log-rank test. A value of p < 0.05 was considered to indicate statistical significance.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesReferences |
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Conversion to sternotomy or a standard thoracotomy occurred in 22 patients (3.6%), of which four (0.7%) were performed under emergent circumstances. The reasons for conversion were an inability to obtain adequate single-lung isolation or declining oxygen saturation in 7, significant ischemia in 5, dense intrapleural adhesions in 4, irreparable injury to the IMA in 4, injury to the subclavian vein in 1, and sudden hemodynamic collapse and ventricular fibrillation in 1. The converted patients were included in the short-term outcomes summary but were excluded from the long-term follow-up analysis.
Postoperative complications within the first 30 days are listed in Table 3. Six (1.0%) early (30-day) postoperative deaths occurred. Three patients died from pulmonary-related complications: a 65-year-old man with necrotizing pneumonia of the left lung on postoperative (POD) 7, an 85-year-old woman with pneumonia of unknown cause at an outside facility on POD 27, and a 77-year-old woman with a massive pulmonary embolism on POD 19. Two deaths were cardiac-related: a 59-year-old man after a large septal infarct and subsequent multiorgan system failure on POD 8, and a 72 year-old woman with a nonischemic cardiomyopathy and history of ventricular tachycardia awaiting defibrillator insertion on POD 15. One additional patient died on POD 21 from a massive colonic hemorrhage. The STS National Database–predicted 30-day mortality for the entire study group was 2.7% ± 0.6% (range, 0.9% to 12.5%).
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display FitzGibbon scores by conduit and target vessel, respectively. A total of 350 LIMA-to-LAD ± diagonal angiograms had the following scores: A, 335; B, 12; O, 3 (A, 95.7%, A ± B, 99.1%). Using the LIMA as a sequential graft to the LAD and diagonal did not compromise the patency scores: an A score of 95.9% (305/318) for the LAD only verses an A score 94.3% (33/35) for the LAD and diagonal sequential graft (p = NS).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesReferences |
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Despite significant technologic improvements in surgical revascularization, the number of CABG procedures performed annually continues to fall, largely attributable to the widespread adoption of drug-eluting stents and the steady progress in drug therapy. Integrated coronary revascularization (hybrid procedure), which takes full advantage of the benefits of both limited-access LIMA grafting to the LAD and catheter-based intervention, may be the only area of potential growth in surgical revascularization; however, such growth partially depends upon long-term data.
This report presents data from a large series on the long-term clinical and angiographic follow-up of the endoACAB technique of coronary revascularization. A central question to ask is what amount of durability is lost, if any, by performing the LIMA-to-LAD bypass using an off-pump and limited-exposure approach? Can we claim that the endoACAB operation and similar approaches are essentially equivalent in their clinical and angiographic success with the conventional approach of grafting the LAD through the comfort and security of a sternotomy on an arrested heart?
Several reports in the past two decades have demonstrated that complete revascularization and use of the IMA have a marked and beneficial influence on long-term survival [13, 14]. Loop and colleagues [15] in 1986 established the LIMA to the LAD as the most salutary and durable revascularization possible for this vessel and its associated territory. The often-cited patency rate for the in situ LIMA graft to the LAD ranges from 90% to 96% at 10 years [16, 17]. Subsequent reports have also demonstrated an additional survival benefit with the use of bilateral IMA grafting [18].
Although the routine use of bilateral IMA grafting has not been widely adopted because of the increased risk of sternal dehiscence, skeletonization of the IMA during harvesting has decreased this risk [19]. One of the inherent advantages of the endoACAB technique is that it completely eliminates the risk of sternal dehiscence or deep sternal wound infection.
The sine qua non of myocardial revascularization, however, lies in its immediate and longer-term success as determined by vessel or graft patency. Although the early experience of percutaneous coronary intervention was characterized by frequent acute failures, the subsequent introduction of bare-metal and drug-eluting stents has markedly improved both the short-term and intermediate-term patency of these procedures. The liberal use of antiplatelet agents has further added to their durability.
Similarly, the intermediate-term patency of grafts constructed using the off-pump approach appears to be equivalent to those of grafts created during arrested heart operations [20, 21], with some studies demonstrating better early left ventricular function using the off-pump technique [22]. Despite these advantages, off-pump surgery through a median sternotomy does not significantly reduce the level of invasiveness of bypass grafting. This glaring limitation has fueled the innovation for alternate approaches of LIMA to LAD revascularization.
Although several techniques for nonsternotomy surgical revascularization are available, only a limited number of reported studies present long-term follow-up [23]. This report documents the reproducibility and excellent angiographic results that can be achieved by the endoACAB technique. Patients in this series had FitzGibbon A or B patency scores of 99.1% at a mean 18 months’ follow-up. This compares favorably with the patency rates of the LIMA-to-LAD using either arrested heart or beating heart techniques.
In this study, we made extensive use of transit time volume flow measurements to ensure immediate graft patency [24, 25]. This practice may have contributed to the excellent patency seen at all time intervals in our group of patients. Although 10-year data is not yet available, previous studies have shown the highest hazard for graft failure is in the early period after revascularization [26]. Further, this study shows that several different revascularization strategies, including sequencing the LIMA, using bilateral IMAs, and total arterial revascularization using radial artery T grafts is feasible with the endoACAB approach.
In summary, the endoACAB procedure offers an appropriate and durable alternative to standard surgical revascularization in selected patients. Either through the use of sequential and composite grafting or combined with percutaneous intervention, multivessel revascularization is possible. In addition, the early and mid-term angiographic results are comparable with standard surgical revascularization, with the potential for a shorter hospital length of stay and total recovery time. Despite many potential patient advantages, there is a significant learning curve for the surgeon. Early success depends on careful patient selection and a step-wise process of acquiring the necessary skill sets for this procedure.
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesReferences |
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In this series, 607 patients received over 700 anastomoses utilizing this less invasive technique, with perioperative and 30-day results similar to those with which we are all familiar from more standard techniques. Eight years ago, the driving force behind this operation must have been "how can we create an IMA-to-LAD anastomosis as minimally invasively as possible?" After all, this particular grafting strategy is the gold standard and portends a clear and well-documented survival advantage. But things have changed a lot in 8 years. While 20-year and longer-term data document the benefits of the IMA to LAD, many of our nonsurgical colleagues believe that 3-year data for drug-eluting stents prove their superiority.
Seenu, in your study, 81% of the patients had single-vessel disease. I would venture to guess that today, more of those patients are being stented and fewer are being referred to you for endoACAB. Perhaps you can comment on this when I am done.
Concerning your manuscript, I would like to just make a few points and I have a few questions. The title of your paper is the "Long-Term Results of the Endoscopic Atraumatic Coronary Artery Bypass." Perhaps an issue of semantics, but I would not classify these data as long-term. Sixty percent of the 607 patients underwent postoperative angiography for graft patency, and that was done at a mean time of only 18 months postoperatively. In addition, the 5-year event-free survival is listed at 92%, but only 14 of the 607 patients have made it out that far to really be examined. I propose that these are early and mid-term results and not long-term. Eighteen months is long-term for stents but not for us.
I have a few specific questions about the data. Two percent of the IMAs were injured during your harvesting. It seems a bit high and I wonder if it reflects the learning curve. Can you comment on the fate of those injured IMAs, and how steep is the learning curve and such that is this something that we can teach our fellows or, in this day and age, is it something that they can likely teach us, or teach me at least?
Only 5% of the 607 patients had triple-vessel disease, and this is really the heart of the matter now. It would seem that in today’s environment, offering this approach to patients with three-vessel disease may be the most productive and beneficial of all, particularly in the terms that the one measurable outcome is the fact that these folks are going home pretty early after surgery. So what I would like to ask is, how likely is this to become a standard operation, particularly for those patients with multivessel disease, who are those more likely to be referred for surgery in this day and age?
Lastly, this study group represented, if I looked at it correctly, about 9% of your total surgical coronary revascularizations during the past 8 years. Are you doing this operation more or less frequently now than you were 3 or 4 years ago, and on whom do you decide to do the operation and how do you think it compares to other less invasive techniques for direct coronary revascularization?
DR REDDY: Thank you, Dr Kern, for those insightful and highly salient comments. Let me try to address them in order.
John raises the important issue of surgical case volume for this procedure, and what we have seen at our institution is that the number of patients referred for single-vessel bypass has actually quintupled. Before we introduced the endoACAB technique, the number of single vessels that were coming to our surgeons were very few, as you point out, but since we have been offering this as an adjunct to other revascularization therapies, it has really grown, and I think it kind of creates its own marketplace.
You raise the point about early, mid-, and long-term follow-up, and certainly when you compare with our colleagues in other specialties, we want to be better, hold ourselves to a higher standard, and I think that the literature is really not concrete in standardizing the lengths of follow-up. We certainly can agree that early follow-up is 30 days, mid- may be somewhere in the 6-month range, but I think 18-month data certainly reflect long-term results when you consider that most coronary artery bypass grafts that fail do so early on. Another way of describing this would be to examine the hazard function in the parametric domain for failure of those grafts; typically in the first 6-month period is the highest hazard for those grafts.
Regarding the point about IMA injury, I think this is a very important point and it is a known possibility, but with thoracoscopic harvest you have x10 magnification. When we are taking the LIMA down in the standard operating setting, we typically use two-and-a-half to four-and-a-half magnification with loops, so you actually get a more precise harvesting of the mammary. And in those cases of injury that you point out, we were usually able to salvage the vessel and use it either with an extension with the radial artery or saphenous vein. You are correct that IMA injury does reflect a part of the learning curve for endoACAB.
The fourth point really is that the endoACAB doesn’t supplant multivessel or arterial grafting via a sternotomy. We see it as an adjunct or, if you will, another tool in the surgeon’s toolbox to offer our patients and referring physicians, and it is something that we have seen grow at our particular institution.
How do you teach this technique? We have had people come and observe, and I think it does take some dedication to mastering the procedure. The case volume is at least 20 to 30 before one can start to feel comfortable. I have performed about 15 of the mammary takedowns myself. The learning curve when I started out was in the 95-minute range and is approaching the 50-minute range.
DR ROBERT S. POSTON (Baltimore, MD): You just mentioned that you used the endoACAB procedure as an "adjunct." Does this include using it as a hybrid procedure with stenting, and if you do, do you use a different anticoagulation regimen in those patients?
DR REDDY: Yes. About 10% of these did represent a hybrid revascularization, if you will, where the patient underwent a mammary to the LAD and then either during the same hospital stay or returning went to the cath lab for a planned stent deployment in another artery, either in the circumflex distribution or the right coronary system.
As far as the anticoagulation regimen, as we indicated, all these patients receive aspirin and then we start them on Plavix after this procedure or after the stent procedure. Heparinization during the procedure is the same as if it was an off-pump or on-pump procedure.
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Footnotes |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesReferences |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesReferences |
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  S. D. Demertzis, M. W. Laschke, F. P.A. Siclari, and M. D. Menger Non-robotic thoracoscopic internal mammary artery preparation in the pig. A training model Interactive CardioVascular and Thoracic Surgery, August 1, 2008; 7(4): 556 - 559. [Abstract] [Full Text] [PDF]
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