Robotic technology has enabled performance of completely endoscopic, closed-chest coronary bypass surgery. During the initial phase, only single-vessel revascularization procedures were carried out, mostly left internal mammary artery (LIMA) bypass grafts to the left anterior descending artery (LAD), and the Food and Drug Administration trial on robotically assisted coronary bypass grafting included only single LIMA to LAD.1 Restricting totally endoscopic coronary artery bypass grafting (TECAB) to single-vessel revascularization severely limits the broader application of the procedure to patients more commonly seen by the community of heart surgeons. One way to deal with this limitation is by combining TECAB-LIMA to LAD with percutaneous intervention (PCI) in so-called hybrid procedures.2–4 However, only a relatively small segment of patients with multivessel coronary artery disease is suited for additional PCI. Therefore, development of multivessel TECAB (mvTECAB) is mandatory. The aim of this review was to give an overview on the history of this complex endoscopic surgery, to outline the current state of development, and to give an impression on potential future developments.
Experimental work in cadavers and animals preceded the clinical introduction of early mvTECAB. A group of pioneers in the field carried out cadaver studies and published the results of these experiments in 2003.5 The feasibility of multivessel endoscopic coronary artery bypass grafting (CABG) was demonstrated on the unloaded and flaccid cadaver heart. Up to four distal anastomoses were performed, and proximal anastomoses were carried out off the ascending aorta. Y-grafts were also constructed. The authors report approaches from both the patient’s left side and the patient’s right side. Transthoracic clamping was used, and several exposure methods for the back wall of the heart were tested. An endothoracic sling seemed to be the most promising approach.
Falk and coworkers6 conducted cadaver and animal experiments in which both the internal mammary arteries were harvested through a transabdominal and a transdiaphragmatic endoscopic approach. Both internal mammary arteries were harvested and anastomosed endoscopically to the LAD and to the right coronary artery (RCA), which were both adequately accessible. Left and right internal mammary artery (RIMA) harvesting times were 48 and 39 minutes, respectively; LAD anastomotic time was 23 minutes; and RCA anastomotic time was 27 minutes. The main challenge with this approach in living animals was a drop of systemic blood pressure in the 30–mm Hg range when the diaphragm was opened. This hemodynamic compromise, however, could be managed by adequate fluid loading.
The first clinical case of completely endoscopic double internal mammary artery (IMA) grafting was reported by Kappert et al7 of Dresden in 2000. Right internal mammary artery to LAD and LIMA to obtuse marginal branch (OM) grafting was carried out on the arrested heart using remote access perfusion and endoaortic balloon occlusion for cardioplegia. Left internal mammary artery and RIMA harvesting times were 48 and 54 minutes, respectively, and anastomotic time was 48 minutes. The total procedure time was 8 hours, and the patient was discharged from the hospital on the seventh postoperative day.
The first double-vessel TECAB procedure on the beating heart was reported by Farhat et al8 of Lyon in 2004. Right internal mammary artery to LAD grafting and LIMA to OM grafting were carried out in a completely endoscopic fashion using the OctopusTE endostabilizer. Of note, this group performed the RIMA to LAD anastomosis first. Procedure time was 6 hours, and the patient was discharged on postoperative day 5.
The first small series of double-vessel TECAB was reported by our group in 2007.9 Double IMA grafting to the LAD and OM branches as described in the first case reports was performed on the arrested heart using the endoballoon for cardioplegia. We exposed the lateral and back wall of the heart using the OctopusTE endostabilizer. A video of the procedure is available in the electronic version of the publication.
CURRENT STATE OF DEVELOPMENT AND CURRENT TECHNICAL CLINICAL APPROACHES
Although double-vessel TECAB has been reported using the first generation robotic surgical systems, it is of utmost importance to have the second and third generations of telemanipulation machines available because robotic instruments used to expose of the back wall of the heart are available only for the later systems.
All operations so far have been performed in general anesthesia using a double lumen endotracheal tube to allow single lung ventilation. Operations from the left side of the patient are much more standardized, and greater experience is available with these procedures. Both internal mammary arteries can be harvested after docking the robotic arms to the patient’s left chest. Detailed information on how to place ports is available in several publications.9–11 After retrosternal dissection, the right pleural space is entered and the RIMA is harvested first.
Skeletonization of the internal mammary arteries is very important for all mvTECAB operations. Adequate length is an issue for a RIMA graft to the distal LAD and for a LIMA graft to the distal circumflex coronary artery. Easier handling of a skeletonized graft can speed up an already complex and time-consuming operation. We have also learned that graft twists or rotations are minimized and can be detected easier after skeletonization. Internal mammary artery harvesting is performed using endoscopic electrocautery at 10 to 15 W. After heparinization, the grafts are clipped distally and detached from the thoracic wall, allowing for autodilatation of the conduits before grafting. Endoscopic removal of pericardial fat can be challenging in obese patients, but opening the pericardium is usually straightforward.
Multivessel TECAB has been reported both on the beating heart10,11 and on the arrested heart.9,12–14 If the operation is performed on the beating heart, a subcostal port is inserted and docked to the fourth arm of the da Vinci Si and da Vinci Si robotic systems (Intuitive Surgical, Sunnyvale, CA USA) through which a robotic wristed endoscopic suction stabilizer is inserted. Using this stabilizer, the lateral wall of the heart can be lifted up, exposing the OMs of the circumflex coronary artery system. Should the patient not tolerate these maneuvers, a supportive heart-lung machine run can be necessary. If an arrested heart technique is chosen, the femoral or axillary arteries are cannulated for arterial perfusion15 and the femoral vein serves as access for venous cannulation. Cardioplegic arrest can be induced either by endoaortic balloon occlusion or transthoracic clamping of the ascending aorta. If remote access perfusion techniques are applied, the patient needs to be free of significant diffuse atherosclerotic disease, especially on the aortoiliac level, the aortic arch, and the ascending aorta, to minimize the risk of stroke and aortic dissection. The main advantage of the arrested heart technique is that the flaccid unloaded heart can be moved and rotated relatively easily, significantly enhancing exposure of the back wall of the heart as compared with a beating heart approach. In addition, both lungs can be deflated during cardiopulmonary bypass, which greatly increases the working space for endoscopic surgery. This technique is especially helpful in obese patients and if the heart is enlarged. As in beating heart TECAB, the robotic endostabilizer can be used to expose the back wall of the heart.14,16 We have most recently developed techniques to expose the RCA from the patient’s left side, thereby allowing exposure of all major coronary artery territories. Studies directly comparing beating heart techniques and arrested heart techniques for mvTECAB have so far not been carried out. Both methods need to be developed to make multivessel endoscopic surgery available for a broader spectrum of patients and surgeons.
Coronary artery graft anastomoses can be carried out using running continuous suture with 7/0 polypropylene,9 single interrupted stitches with U-Clips,10 and automatic connector devices.11
The most straightforward version of mvTECAB is placement of an in situ RIMA graft to the LAD and an in situ LIMA graft to an OM branch. Sequential grafting of the LAD and a diagonal branch is well established and was reported by Dogan et al12 from Frankfurt relatively early in procedure development. Sequential LIMA grafts to the anterior wall of the heart do not need specific exposure techniques. Concerning the sequence of completing the anastomoses, both “LIMA to the LAD first” and “side-to-side anastomosis to diagonal branch first” have been reported. In beating heart TECAB, we perform the side-to-side anastomosis first because flow into the diagonal branch can be measured and free flow of the distal LIMA can be assessed before the LIMA to LAD anastomosis is carried out. We have noticed that on the arrested heart, the side-to-side anastomosis to the diagonal branch is relatively easy to perform if the LIMA to LAD anastomosis is already in place. As mentioned earlier, skeletonization significantly enhances graft handling especially if sequential anastomoses are performed. Sequential grafting of two OMs has been described by our group.14,17,18
Most recently, construction of endoscopic arterial Y-grafts has become feasible. We regard this as an extremely important step in procedure development. For construction of these Y-grafts, the recipient artery is clipped to the pericardial fat and the endostabilizer is used to immobilize the recipient artery. After placement of an endoscopic bulldog clamp, the artery is incised. The free contralateral internal mammary or a radial artery can be sutured to the recipient artery to form a Y-graft construct. Y-grafts have significantly enhanced the armamentarium of robotic coronary surgeons. Quadruple bypass grafting has most recently been carried out by our group using Y-graft techniques. The postoperative angiogram of a patient who underwent robotic totally endoscopic triple CABG using both Y-grafting and sequential grafting techniques is shown in Figure 1.
In endoscopic mvTECAB from the right side, both the LAD and the posterior descending artery can be reached. Transthoracic pericardial traction sutures, secured on the left side of the chest, may facilitate rightward rotation of the heart and improve exposure of the LAD. The endostablilizer, which is brought into the chest through a subxiphoid port, can adequately expose both the LAD and the posterior descending artery. In cases of an ostial or very proximal RCA lesion, RIMA to RCA may be combined with LIMA to LAD. If more distal RCA lesions are involved, the best option is to place the RIMA to the LAD and construct a Y-graft off the RIMA to the RCA system.
Endoscopic total arterial grafting is one of the main advantages of mvTECAB, but in patients with subclavian artery stenosis or in patients with a pathologic Allen test, vein grafts are indicated. Our group has developed venous coronary bypass grafting off the left axillary artery.17 Other teams have endoscopically constructed aortocoronary vein grafts (Didier de Canniere and Jean-Luc Jansens, Erasme University Brussels, personal oral communication).
At the current stage of procedure development, double-vessel TECAB is reproducible and can be performed with a high comfort level. Triple vessel TECAB is feasible especially using arrested heart techniques, but quadruple bypass is a high-end procedure that remains under development.
INDICATIONS AND CONTRAINDICATIONS
Any patient with a clinical indication for open multivessel CABG can be considered for TECAB at advanced centers.
Suitable Coronary Morphology
Sequential LIMA LAD/Dg grafting is mostly performed in patients with complex bifurcation lesions of the LAD and diagonal branches. Double IMA grafting to the left ventricle is indicated for patients with left main disease or patients with significant stenoses of the LAD combined with significant stenoses of the circumflex coronary system. If additional significant RCA lesions are present, a radial artery can be taken off the LIMA or RIMA as a Y-graft and sutured to the posterior descending artery.
All versions of mvTECAB can be combined with PCI’s to coronary targets suited for PCI. Jansens et al18 described the first case of such a complex intervention. We consider these operations “advanced hybrid coronary interventions.”3,4 It can be anticipated that combinations of robotic endoscopic mvTECAB and (multivessel) PCI will be an integral part of integrated approaches to treatment of complex multivessel disease with high SYNTAX scores. The advantages of hybrid coronary interventions as compared with open multivessel coronary bypass surgery are preservation of sternal integrity and a faster postoperative recovery.
Indications for double-vessel TECAB performed from the right side of the patient are less common. Usually, a significant LAD lesion is present in combination with a significant lesion of the RCA system.
Absolute and Relative Contraindications
General contraindications for TECAB must be considered. We regard the following clinical situations as absolute contraindications: acute myocardial infarction, cardiogenic shock, severe pulmonary disease that precludes prolonged periods of single lung ventilation, and significant chest deformities. Relative contraindications are redo operations and a history of radiation therapy to the chest, severe chest trauma, pericarditis, or pleuritis. Morbidly obese patients can basically be considered. In some of these patients, however, intrathoracic space can be very limited and technical challenges should be expected. One advantage in this patient group is that both internal mammary arteries can be used despite a significant risk of deep sternal wound infection. Patients with chest wall deformities such as pectus excavatum or kyphoscoliosis should be avoided. Contraindications relating to specific surgical techniques include intramyocardial target vessels for beating heart multi-vessel TECAB and contraindications for application of remote access perfusion and aortic balloon endo-occlusion for arrested heart multi-vessel TECAB such as a dilated ascending aorta or significant aortic atherosclerosis.
It can be recommended that low-risk patients without significant comorbidities are chosen during a single surgeon or team learning curve. Procedure times will be prolonged and multimorbid patients will tolerate neither technical errors nor extensive operation times.
Overall, 161 cases of mvTECAB are published in the literature (Table 1). Most publications do not report on outcome stratified for multivessel approaches.
The mvTECAB experience of the University of Maryland Medical Center and Innsbruck Medical University from 2001 until 2011 is 196 cases. Table 2 shows the demographic patient profile, and postoperative outcomes are outlined in Table 3. The procedures required operative times in the 6-hour range. Perioperative results are within those of CABG or off pump coronary artery bypass (OPCAB) through sternotomy. Long-term survival and freedom from major adverse cardiac and cerebral events at 5 years (96% and 73%, respectively) seem to meet the standards of open CABG or OPCAB through sternotomy (Figs. 2 and 3). The current SYNTAX trial, a prospective randomized trial comparing CABG and PCI for multivessel disease, reports 4-year survival of 96% and 4-year freedom from major adverse cardiac and cerebral events of 76% in the surgical revascularization arm.
We have previously shown that in mvTECAB, operative times are longer,19 conversion to larger incisions is more frequent,20 and blood transfusion rates are higher21 as compared with single-vessel TECAB. In an early series, Dogan et al12 reported longer operative time, longer ventilation time, and longer hospital stay for sequential double-vessel TECAB to the LAD and diagonal branches. Nevertheless, Srivastava et al10 have suggested that mvTECAB is a good option in selected patients, and Balkhy et al11 state that multivessel beating heart TECAB is feasible in patients with lesions of the LAD, the diagonal branches, and high OMs although the RCA system is difficult to reach.
Figure 4 shows patient recovery after mvTECAB. Full activity including sports is usually reached within a 6-week timeframe, which is shorter than the usual 10 to 12 weeks of sternal precautions commonly recommended after open surgery. Previous studies on robotically assisted coronary bypass surgery have already shown dramatically shortened rehabilitation times as compared with CABG or OPCAB through sternotomy.22,23
MAIN ADVANTAGES, DISADVANTAGES, AND CURRENT OVERALL VALUE
The development of mvTECAB represents a breakthrough in minimally invasive surgical coronary revascularization. This step is absolutely necessary to establish endoscopic coronary bypass surgery on a broader basis. If TECAB is restricted to single LIMA to LAD grafting, this method will certainly not survive because the current referral patterns in cardiac surgery practice predominantly include a high volume of complex multivessel disease. Applying the procedures described in this review can open the doors into this patient segment. The main advantages of mvTECAB are reduced surgical trauma and preservation of patient integrity; TECAB makes coronary bypass surgery less destructive. This approach leaves the sternum completely intact, which allows bilateral IMA use even in groups at risk of sternal wound infection, such as patients who are obese, patients with diabetes, and patients with chronic obstructive pulmonary disease. Reduced trauma mainly translates into shorter recovery time. Disadvantages include prolonged operative times, significant equipment and disposable costs, and operator learning curves, which can reach three-digit case numbers until a stable phase is achieved.24,25
It was only 13 years ago that TECAB programs were started. During this short period, a third generation of robotic surgical devices was developed, and mvTECAB up to triple and quadruple bypass grafting26 has become a reality. It can certainly be anticipated that significant further technological development will happen. The specific needs for mvTECAB include procedure-specific instrumentation for exposure of the back wall of the heart. Dual console systems, which are already available, will allow teaching of new robotic cardiac surgeons and also carry a potential for endothoracic robotic assistance, which can probably speed up surgical maneuvers further and make the procedures faster.27 Smaller automatic connector devices that are easier to handle than the currently available systems will be developed but will not excuse surgeons from intense practice of endoscopic surgical maneuvers, such as tissue dissection, graft preparation, and most importantly, endoscopic suturing. Simulation will play a major role in this learning process, and special training centers that can dampen the clinical learning curves will be established. Concerning surgical complexity, mvTECAB is comparable with thoracoabdominal aortic replacement, a Ross procedure, or an arterial switch operation. Therefore, this type of surgery will probably be restricted to super-specialized surgeons and fully dedicated teams. Because of the huge prevalence of multivessel coronary artery disease, however, it is not unrealistic that a significant percentage of coronary bypass surgery in the next decades will be performed in robotic endoscopic fashion.
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