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J Thorac Cardiovasc Surg 2000;119:221-229
© 2000 Mosby, Inc.
SURGERY FOR ACQUIRED CARDIOVASCULAR DISEASE |
From the Departments of Cardiac Surgery,a Anesthesiology,c and Biostatistics,d Montreal Heart Institute, and the Department of Cardiac Surgery,b University of Montreal, Montreal, Quebec, Canada.
Address for reprints: Raymond Cartier, MD, Montreal Heart Institute, Research Center, 5000 Belanger St E, Montreal, Quebec, Canada H1T 1C8 (E-mail: cartierr{at}icm.umontreal.ca) .
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Abstract |
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 Top Abstract IntroductionPatients and methodsResultsDiscussionConclusionAppendix: DiscussionReferences |
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsDiscussionConclusionAppendix: DiscussionReferences |
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1 in the early 1960s, the technique has recently regained surgeons’ attention as a minimally invasive and alternative approach to conventional operation. By avoiding sternotomy in favor of a small anterior thoracotomy, minimally invasive direct coronary artery bypass grafting (MIDCAB) rapidly attracted interest as a new technique, albeit limited mostly to patients with single-vessel disease. 2 Consequently, the surgeons’ focus in minimally invasive technique rapidly shifted toward the avoidance of cardiopulmonary bypass (CPB) rather than the sternotomy itself to potentially treat the significantly larger number of patients affected with multivessel disease. Long considered the gold standard, CPB-supported coronary operations are recently being questioned because the procedure is still characterized by a significant number of side effects. 3,4
Initially, the beating heart operative technique was deemed to be more technically demanding; however, the recent introduction and continuous improvement in coronary mechanical stabilizers has considerably improved the feasibility and outcome of these procedures. Although the beating heart operative technique was shown to be a suitable alternative to conventional CPB operations in select patients carrying high surgical risk, it has not been considered on a systematic basis for a majority of patients. 5
To qualify as an alternative approach to conventional operations, beating heart operations must respond to all anatomies, use similar vascular conduits, achieve equivalent technical results and comparable mortality and morbidity rates, and maintain a low conversion rate to on-pump operations. Furthermore, the ability to provide the patient with as complete a coronary revascularization as possible should not be compromised through the beating heart operation approach because this represents a major benefit for the patient. 6,7 Since October 1996, we have developed and adopted the practice of systematic off-pump coronary artery revascularization at the Montreal Heart Institute. This report describes our experience with this technique while comparing it with conventional CPB operations.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsDiscussionConclusionAppendix: DiscussionReferences |
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Surgical contraindications for beating heart operations.
After the first 30 off-pump bypass procedures, all patients were considered as potential candidates. Only patients (<1%) with deep intramyocardial left anterior descending (LAD) arteries or with very unstable preoperative hemodynamics were not considered for the procedure. Reoperative procedures, during which patent but atheromatous grafts fed occluded native coronary arteries, were considered relative contraindications if partial aortic clamping of the ascending aorta was anticipated, thereby causing a potential ischemic threat.
Off-pump surgical technique.
The technique we used has already been described. 8,9 In brief, most of the procedures (>99%) were approached through a standard sternotomy under general anesthesia (narcotics, benzodiazepines, and pancuronium). Occasional boluses of metoprolol were administered to maintain heart beat below 80 beats/min when indicated. Pressure drop and electrocardiographic ST-segment modifications were treated with infusion of phenylephrine and nitroglycerin, respectively, as indicated.
The distal right artery and the LAD artery were directly accessed with very little heart manipulation. The posterior descending artery (PDA) and the obtuse marginal artery were accessed by more extensive mobilization of the posterior pericardium. For the circumflex territory, this consisted in positioning 4 traction sutures spaced between the left superior pulmonary vein and the inferior vena cava (Fig 1). The sutures were placed far below the phrenic nerve at the level of the pericardial reflection. No pericardial counterincision to create heart herniation through the right chest was used and in none of the cases was the need for a right ventricular assist device necessitated. Vessel occlusion was achieved through external encircling with silicone rubber bands (Retract-o-tape; Quest Medical Inc, Allen, Tex). No intraluminal occlusive device, shunt, or gas insufflation was used. Coronary artery immobilization was achieved with specially designed reusable mechanical stabilizers (Cor-Vasc System [patent pending]; CoroNéo Inc, Montreal, Canada; Fig 2, A and B ).
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On-pump surgical technique.
Coronary revascularization with CPB was performed under moderate hypothermia (32°C-34°C) with a membrane oxygenator (Monolyth; Sorin Biomedica, Inc, Richmond Hill, Canada) equipped with an arterial air filter (Terumo; CardioMed Supplies, Inc, Gormley, Canada). Cardioplegic arrest was achieved with a hyperkalemic cold cardioplegic blood solution. In the majority of patients, the CPB circuit was primed with crystalloid solution.
Follow-up.
Short-term (3 months) follow-up was completed on 99% of the beating heart operation group. However, midterm (>6 months) follow-up was completed only in 30% of the patients.
Statistics.
Data are expressed as mean values ± SD. Comparisons between the two groups are established with unpaired t tests (2-tailed) for continuous variables and with the 
2 and Fisher exact tests for discrete variables. For data presenting skewed distribution, results are expressed as the median and 25th and 75th percentiles along with minimum and maximum, and the Kruskal-Wallis test is used for statistical comparisons. For continuous variables studied in different time frames, a 2-way analysis of variance for repeated measures on factor time was used.
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Results |
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TopAbstractIntroductionPatients and methodsResultsDiscussionConclusionAppendix: DiscussionReferences |
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Recurrence of angina.
Five patients in the beating heart operation group experienced early (<2 months) recurrence of angina. One patient had an acute occlusion of a PDA graft on the third postoperative day. He underwent a successful percutaneous transluminal coronary angioplasty of the distal right artery. Interestingly, the distal anastomosis was patent and was not related to the technical failure of the bypass. Three other patients underwent follow-up coronary angiograms 3 to 6 months after the operation. Of these, 2 showed patency of all grafts with diffused disease. One showed occlusion of two vein grafts made on an endarterectomized PDA and a third obtuse marginal artery. These vessels were of small caliber (1.25 mm) and were described as diffusely atheromatous. These 3 patients were treated medically. Another patient, who did not have a follow-up angiogram but did have a nuclear stress test, had a localized ischemic area and was also treated medically.
Two patients had midterm (>2 months) recurrent angina. One was reinvestigated by angiography. A venous graft stenosis was found (2 cm from the proximal aortic anastomosis), and a successful percutaneous transluminal coronary angioplasty was performed. The other patient was treated medically. Both are in New York Heart Association functional class I.
Midterm mortality rates.
We report 9 midterm deaths (>1 month) in the beating heart operative technique groups, and causes of death are presented in Table VIII. There were only 2 cardiac-related deaths. An 86-year-old patient died of chronic heart failure subsequent to multiple pulmonary emboli. Unfortunately, this condition was diagnosed only after the heart operation. Another patient died 2 months postoperatively because of chronic heart failure.
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Discussion |
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TopAbstractIntroductionPatients and methodsResultsDiscussionConclusionAppendix: DiscussionReferences |
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In terms of its applicability, the MIDCAB procedure is mostly limited to patients with single-vessel disease, which, for the average practice in our experience, represents about 5% of the cardiac operation caseload. The conventional sternotomy, in addition to providing surgeons with an accustomed approach, allows them to concentrate on the prime task (ie, CABG on the beating heart). This is probably an easier first step in evolving cardiac operations toward a less invasive procedure by the elimination of CPB. Next, steps can focus on achieving this beating heart operative procedure through smaller incisions or port incisions. A conventional sternotomy provides access to all coronary territories, thereby allowing full or complete revascularization. More important, the retracted rib cage allows the surgeon the ability to "verticalize" the beating heart to gain access to the posterior arteries. Considering that more than 70% of the surgical candidates have triple-vessel disease, this beating heart approach with conventional sternotomy is clearly applicable to a larger group of patients.
Since the beginnings of CABG operations for coronary atheromatous disease, the off-pump approach has always been present. Anecdotally known in the 1950s, 10 the beating heart operative technique was really launched by Kolesov 1 in the 1960s. Even with the introduction of CPB, some surgeons continued, mainly for economic reasons, to perform beating heart operations and reported extensive series with excellent results. 11-13
Avoiding CPB is a major step in rendering CABG less invasive. The inflammatory reaction initiated by CPB has always been seen as a significant threat. 3 CPB initiation activates the contact system to produce kallikrein, a powerful neutrophil activator. The complement system is also activated, producing anaphylatoxin C3a, C4a, and C5a, all of which are vasoactive substances. The activated neutrophils can potentially release many cytotoxic enzymes, and the monocytes, although more slowly activated, express tissue factor that initiates the extrinsic coagulation pathway. All these substances cause edema, decrease myocardial contractility, change vascular resistance, and mediate the principal complications of CPB, such as bleeding, thromboembolism, fluid retention, and temporary organ dysfunction. 14
In the present study two comparable cohorts of patients in terms of age, sex distribution, and preoperative risk factors underwent two different CABG techniques. Only the prevalence of unstable angina was slightly more prominent in the CPB group. The two groups had a comparable average number of grafts performed per patient, with similar graft distribution relative to the different coronary territory being grafted. The rate of complete revascularization was greater than 90% in the beating heart operation group, and conversion to CPB was inferior to 1%. Average ischemic time was less in the beating heart operation group than in the CPB group. Operative blood loss was substantially lower in beating heart operations, as reflected by a transfusion need that was halved in this group. Furthermore, among the patients receiving transfusions, fewer derivative blood products were administered in the beating heart operation group. Postoperative and discharge hemoglobin count was significantly higher in the beating heart operation group, whereas the rise in postoperative creatinine level was very low compared with the CPB group. There was a significant trend toward a better myocardial preservation in the beating heart operation group as outlined by the lower rise in postoperative CK-MB and a less frequent need for intra-aortic balloon pumps for left ventricular assistance. This has already been reported by Pfister and colleagues 13 in a matched case study, as well as by others. 15,16 The operative mortality rate was comparable in both groups; however, a larger proportion of deaths in the CPB group was due to postoperative low cardiac output syndrome. The rate of perioperative MI, which includes Q-wave and non–Q-wave infarction, was similar in the two groups, suggesting that this complication is not dependent on technique.
Of notable interest among postoperative complications is the incidence of atrial fibrillation (AF), which was comparable to the incidence reported by others under similar circumstances. 17 In contrast, Galloway and coworkers, 18 who recently published the first report of the Port-Access International Registry, reported a 5% rate of new onset of postoperative AF with Port-Access CABG (with CPB). Being proposed as a possible explanation for this decreased incidence is the absence of right atriotomy incision and suture line, as well as fewer atrial manipulations with the Port-Access technique. Because right atrial manipulations are minimal during beating heart operations, it is our opinion that some other explanation may have to be given. The length of the pericardiotomy might be a factor because it is minimized during Port-Access operations.
There was no difference in the incidence of inotropic support after the operation, infection, reintervention for either postoperative bleeding or sternal dehiscence, and cerebrovascular accident (CVA) in both groups. However, the two CVAs that occurred in the beating heart operation group were noted 4 and 5 days postoperatively subsequent to an AF episode. No case of deep mediastinitis occurred in the beating heart operation group, and no patient had acute respiratory distress syndrome. Pulmonary complications reported (10%) include prolonged intubation (>24 hours), persistent atelectasis, and pneumothorax. This latter complication seemed more frequent than expected and may be related to the placement of the deep pericardial sutures. During this maneuver, it is imperative to deflate the lung to decrease the risk of damage from the pericardial suture needle. The surgeon must be aware of this possible complication and leave the pericardium penetration as superficial as possible.
The low-CPB conversion rate reported in this series is due to the strict adherence to the revascularization strategy adopted from the onset of this series. It consists of beginning with the most collateralized vessel and providing forward flow in the graft as soon as possible to serve as a vascular backup for the next generally less-collateralized target vessel. All proximal anastomoses were completed in the same partial side-clamping. Furthermore, avoiding the crossclamping of the distal right coronary artery in case of noncritical stenosis decreased the incidence of intraoperative ventricular block. Occasional crossclamping of the inferior vena cava by external snaring was found to be complimentary in the control of temporary rise of pulmonary pressure with left ventricular overload. This maneuver afforded time for the anesthesiologist to readjust the intravenous nitroglycerin infusion, as well as fluid administration.
The circumflex approach developed with deep pericardial sutures allows the displacement of the heart without having to directly manipulate the left ventricular wall. This, combined with Trendelenburg positioning of the patient, contributed to maintaining stable hemodynamics, as reported experimentally. 19 Hypothermia, a problem that we initially encountered, was successfully managed by raising the room temperature, using an intravenous fluid rewarming device, and occasionally using a commercial warm-air ventilated hood device to cover the head and shoulders of the patient.
Limitations of the study.
This study has significant limitations. Most important, no systematic control coronary angiographies were performed, albeit for economic and logistic reasons, thereby limiting the assessment of the beating heart operation itself. The first 12 patients were studied, and initial results were good (100% patency; 95% good anastomotic result), encouraging us to pursue this approach, which was, at the time, novel. 20,21 The fact that the CPB cohort had to be chosen from a noncontemporary period might obscure the comparison in hospital stay between the two groups given the recent trends associated with more aggressive discharging. Also, only the short-term clinical follow-up has been completed, and therefore it is possible that other angina recurrences have not been reported. Finally, only a real randomized study with angiographic control and long-term follow-up will confirm or disprove the value of this procedure.
Areas of caution.
We found the treatment of patients with moderately enlarged ascending aorta (4.0-4.5 cm) that do not necessitate aortic replacement to be a significant area of caution. These patients do not tolerate side-clamping well, which is likely to lead to aortic dissection. Two dissections occurred in this series, and one was repaired immediately during the initial operation. The other patient was discharged and returned 1 week later with an acute dissection at the site of the clamp; the patient died during the surgical attempt to correct the dissection. Both patients had a moderately enlarged ascending aorta.
Reoperative operations were occasionally problematic when a patent venous graft fed a native occluded artery. The side-clamping of the aorta is poorly tolerated in these circumstances, and the surgeon has to rely on internal thoracic arteries when they are available. Another problematic situation relates to ischemic mitral insufficiency. Although CABG can be performed by using the beating heart operative approach in these cases, it does not alleviate the need for a mitral annuloplasty. We now routinely do intraoperative stress transesophageal echocardiography to determine the need for such a procedure.
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Conclusion |
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TopAbstractIntroductionPatients and methodsResultsDiscussionConclusionAppendix: DiscussionReferences |
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Appendix: Discussion |
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TopAbstractIntroductionPatients and methodsResultsDiscussionConclusionAppendix: DiscussionReferences |
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Over 25 years at New York University (NYU), early on some patients would have an off-pump bypass through a sternotomy, such as those patients who had a failed angioplasty procedure or patients who were operated on through the left side of the chest for obstructions in the circumflex graft that needed an isolated marginal bypass.
Currently, all surgical modalities are being used: sternotomies with CPB, blood cardioplegia or cold fibrillation, off-pump bypasses, Port-Access operations, MIDCAB, and transmyocardial revascularization. About 45% of the patients now have traditional bypass procedures, 25% have Port-Access operations, 25% have off-pump CABG, and about 5% have MIDCAB. There has been a recent rise in the percentage of off-pump procedures with improved stabilization, such as suction in the Octopus II tissue stabilizer (Medtronic, Inc, Minneapolis, Minn), mechanical devices, "misters," and improved tricks for exposure.
Most of us at NYU believe that minithoracotomies for mitral and aortic valve surgery have significant benefits, and we have somewhat of a bias toward minithoracotomies. We generally use off-pump CABG for our increasing patient population with increased risk, such as the atheromatous aorta or hepatic or renal insufficiency, including patients requiring liver transplantation and those needing revascularization before those procedures.
Our results with Port-Access cardiac bypass have shown excellent results with excellent patency. Hospitalization and transfusion costs are reduced, and recovery is quicker.
This excellent study has tremendous potential but really does not show much in the way of decreased mortality or morbidity rates. Still, there is a significant problem with dissections, wound infections, and the need for inotropic agents, as well as respiratory problems, despite not using the pump.
There is an expanding use of this approach with improved technology, and I think that in a subset of patients, it has tremendous application. However, we must be cautious of the outcomes because early reports have shown late problems with some of the grafts that were done on the beating heart compared with those done with CPB.
Clearly, there is a subset that can be best treated with off-pump CABG, but it remains to be seen what the benefits are supposed to be for all patients if complications remain comparable with coronary bypass operations done on-pump, given the better long-term results that we have all seen with CABG done while on-pump.
Dr Cartier. Thank you, Dr Colvin, for your remarks. I agree with you that we will need a long-term study to confirm these findings, but I would say that the task of beating heart surgery is not necessarily to show that it is a better procedure than the standard operation but that it is at least as good. If we can just prove that, it will be something that is very interesting. We can decrease the cost, we can decrease the transfusions, and I believe that for the older patient, outcomes are going to be better.
It is obvious that the Heartport technology (Heartport, Inc, Redwood City, Calif) with the minithoracotomy coupled with the fact that you can do 3 or 4 bypasses through a small thoracotomy could be very interesting to the young population, and I would be very happy to do a study in which these two technologies are compared.
However, as you know, the Heartport technology has not been introduced in Canada yet, and therefore it is not something we have been able to do. In the future, however, I believe we will be able to compare these two techniques and find out which is the worst for younger patients, sternotomy or bypass, and which is the best for the older patients.
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Footnotes |
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References |
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TopAbstractIntroductionPatients and methodsResultsDiscussionConclusionAppendix: DiscussionReferences |
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