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Eur J Cardiothorac Surg 2000;17:38-45
© 2000 Elsevier Science NL
a Department of Cardiac Surgery, Heartcenter, University of Leipzig, Russenstrasse 19, 04289 Leipzig, Germany
b Department of Anesthesiology, Heartcenter, University of Leipzig, Russenstrasse 19, 04289 Leipzig, Germany
Corresponding author. Tel.: +49-341-865-1421; fax: +49-341-865-1452
e-mail: falv{at}.medizin.uni-leipzig.de
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Abstract |
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 Top Abstract 1. Introduction2. Methods3. Results4. Discussion5. ConclusionAppendix A. Conference...References |
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Key Words: Coronary artery bypass grafting • Computer enhanced surgery • Robotics • Telemanipulation • Endoscopy
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1. Introduction |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionAppendix A. Conference...References |
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2. Methods |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionAppendix A. Conference...References |
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The surgical manipulators on the instrument arms have three degrees of freedom (pitch, yaw and insertion) and provide motion coupling to the end-effectors, exchangeable surgical instruments. These instruments provide another three degrees of freedom by means of a mechanical wrist for a total of six degrees of freedom (DOF). Additionally, tool actuation is provided at the tip of the instrument allowing for free motion in three-space. The system provides motion scaling, tremor filtering and the possibility to disconnect the slave from the master which enhance the precision, provide optimal hand-eye alignment and favorable ergonomics (Fig. 1). The vision system features a true 3D-imaging system with two separate optical channels. Two 3 chip CCD cameras with 800 lines of resolution are used. The images are presented directly in the viewer on two continuous tone CRT monitors. Resolution of the scope is 2.0 mrad/line pair. The surgeon controls the camera by pressing the footswitch that locks the slave tool manipulators in place and gives the surgeon control of the camera by means of the master manipulators. This method of controlling the endoscope provides for easy and fast positioning of target anatomy in the image while keeping the slave tool tips in the operator's view. A detailed description of the system is provided elsewhere [7–9].
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2.3. Group I
A standard coronary artery bypass grafting (CABG) procedure via a median sternotomy and using cardiopulmonary bypass (CPB) was performed in 12 patients (Mean age 63±11 years, seven male), with two- (three) or three-vessel disease (nine) requiring multi vessel grafting. After conventional graft harvesting the patient was placed on cardiopulmonary bypass, the distal anastomoses to the obtuse marginal branches and the right coronary artery were performed manually using vein grafts, radial artery or right ITA grafts. The left ITA to left anterior descending artery (LAD) anastomosis was performed remotely using the da Vinci system through the sternotomy incision as described elsewhere [7].
2.4. Group II
Group II consisted of 32 patients (mean age 61±10 years, 20 male, mean ejection fraction 58±14) with an indication for single vessel grafting of the LAD. Patients were placed in a supine position with the left chest slightly elevated by a roll. The left arm was lowered beyond the level of the posterior axillary line. Double lumen intubation was performed and standard monitoring and intravenous anesthesia was applied. The ITA was first harvested endoscopically with the system. After the left lung was deflated, a 12 mm Sealing-Port (Ethicon, Cincinnati, OH) was inserted at the 4th intercostal space (ICS) in the anterior axillary line. Continuous CO2 insufflation was initiated and continued up to an intrathoracal pressure of 10 mm of mercury, depending on patient tolerance. A 30° scope was inserted through the port and the course of the LAD was identified. Two instrument ports were created at the 3rd and 6th ICS above the anterior axillary line (Fig. 2) and the da VinciTM system was placed on the patient's right side. The operation was continued from the master console. The ITA was dissected using low energy cautery (15 W). Only large side branches were clipped. Proximally, dissection was performed laterally to the phrenic nerve and medially up to the first rib. Distally, dissection was performed up to the 6th ICS. After ITA dissection was finished, the system was withdrawn the patient was heparinized. A small anterolateral minithoracotomy was performed in the 4th ICS. A left anterolateral minithoracotomy was then made and the procedure was completed as a MIDCAB operation. For stabilization the Estech or Autosuture mechanical stabilization devices were used. Temporary proximal occlusion of the LAD was by snaring the vessel with a pledgeted 4.0 Prolene suture. Intraoperatively graft flow was measured using transit time Doppler flow probes.
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ITA take down was performed as described above for group II. The distal end of the ITA was then skeletonized and prepared for the anastomosis in situ. The distal ITA was dissected free from its concomitant veins and fascia leaving those intact in order to provide counter-traction for further manipulation (cutting and trimming) and keeping the tension from the ITA. The internal thoracic veins were then clipped. At 2–3 cm proximal, the ITA was partially skeletonized for placement of a vascular clamp.
The pericardial fat was removed using cautery. The pericardial incision was begun at the mediastinal attachment and enlarged laterally so that by gravity the fat pedicle would widen the pericardial incision. The LAD and its collateral branches were identified. A marker clip was placed medially to the LAD. After the site of anastomosis was determined and sufficient ITA length for grafting was confirmed, the patient was fully heparinized. A fourth port was created in the 4th ICS in the midclavicular line and a trocar inserted. An angled vascular clamp (Scanlan, St. Paul, MN) was inserted through this port and placed on the proximal skeletonized portion of the LAD. The distal ITA was clipped, cut and trimmed but still left in situ still being attached by its concomitant veins. Flow was verified by briefly opening the vascular clamp. The right groin was dissected for cannulation for femoro–femoral bypass and placement of the Heartport endoaortic clamp as has been described elsewhere [11]. For best visualization of the anastomotic site the scope was switched to a 0° scope or 30° angled down, subject to the individual's anatomy. After cardiac arrest was established, the ITA was detached and positioned at the anastomotic site with a 6-0 Prolene stay suture. The LAD was prepared using blunt and sharp dissection. The arteriotomy was made using a sharp blade and extended using Potts scissors while administering cardioplegia with high pressure. The anastomosis was performed using custom-made 8-0 Prolene suture (double armed, 7 cm of length) as described elsewhere [7]. The pedicle was fixed to the epicardium using a 6-0 suture. Before the vascular clamp was released the anastomosis was tested for leakage by running cardioplegia. The endoclamp was deflated and rewarming begun. During rewarming of the patient, angiography of the graft was performed using a 5 Fr ITA catheter (Baxter, Irvine, CA) via the left femoral artery. A single chest tube was inserted. The left lung was inflated and incisions were closed. The patient was then weaned from CPB and cannulae removed.
The institutional ethics committee approved the study protocol and all patients gave written informed consent.
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3. Results |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionAppendix A. Conference...References |
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3.2. Group II
In 31/32 patients (96%) ITA harvest was successfully performed with the system at a mean time of 61±27 min. There was a substantial learning curve associated with ITA take-down (Fig. 3). Currently, take down time is 40–50 min. In two additional candidates for endoscopic ITA take down, the ITA could not be harvested due to pleural adhesions and or insufficient space between the mediastinum and the sternum despite CO2 insufflation. Time for anastomosis was 16±6 min. Flow measurement revealed graft patency in all but one case (mean graft flow 42±17 ml/min). One patient had insufficient ITA graft flow after dissection. This patient underwent an additional sternotomy and had a vein graft placed on the LAD on the beating heart. Inspection of the discarded ITA revealed an intimal dissection at the mid portion of the graft. One patient had a left hematothorax which required re-exploration. The root cause was bleeding from a side branch which was repaired by a clip. In two patients skin emphysema developed postoperatively that required prolonged chest tube drainage. Postoperative angiography (between POD day 3 and 6) demonstrated graft patency in all cases.
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4. Discussion |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionAppendix A. Conference...References |
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4.1. Patient selection
Patients with left ventricular dilatation or anterior wall aneurysms after infarction are not ideal candidates for endoscopic bypass grafting because of the limited space between the heart and the sternum. In our series two patients with enlarged left ventricles after anterior MI's had to be converted to a MIDCAB procedure because despite CO2 insufflation up to an ITP of 12 mm of mercury not enough working space for ITA harvest could be created. In the beginning we tried to identify the ideal anatomy for TECAB. In general, a larger chest is desirable since it allows a larger triangle for port placement, which helps to minimize the risk for collisions. A relation between the ease of performance and the shape of the chest (barrel shaped, flat) could however not be established. Also the body-mass-index is not predictive for performance since it does not take into consideration fat distribution. In women large breasts may alter port placement. In general this should not exclude these patients from the procedure, especially in the light of the reported incidence of wound complications in obese women undergoing MIDCAB [16].
4.2. Patient positioning
To avoid external collisions between the arms we think that a supine position with a slightly elevated left shoulder and little table rotation towards the right works best. The left arm should be lowered, as less collisions occur compared to an overhead position. In addition, the risk of plexus injury that has been reported with the left arm placed over the head is minimized [6]. At our institution a radiolucent table is used to allow for intraoperative coronary angiography that we found to be very valuable for immediate quality control especially in TECAB procedures.
4.3. Port placement
The importance of optimal port placement has been emphasized by Loulmet and others before [6]. Port placement differs as compared to what has been described for manual endoscopic ITA takedown procedures [17–19]. This is mainly due to the fact that a large triangle minimizes the risk for collisions between the arms. Also, given the current system configuration with all three arms mounted on one cart, the camera is always in the center. Despite the relatively high position of the ports, motion of the right instrument arm is sometimes restricted by the patient's left shoulder while dissecting the distal end of the ITA. It is important to have in mind that using a telemanipulator one is able to work in an ambidextrous manner. It is advisable to switch hands (i.e. work with cautery in the left hand at the distal portion of the ITA) when collisions (i.e. with the patients shoulder) limit the range of an instrument. This may also be helpful during the anastomosis, as some stitches are easier to perform with the left hand. Modified instruments are currently being introduced to allow a wider range of motion inside the chest. In addition an additional stand alone left sided cart for the camera arm has been successfully applied to clear the room between the instrument arms. A longer distance between the entry point and thus the remote center and the working field will theoretically minimize the risk of collisions between the manipulators. We have explored the possibility of a right side approach which has been beneficial in the cadaver lab. In one TECAB patient, port placement was mirroring the left sided approach. The right lung was deflated and the mediastinum was taken down. Coming from the right, view of the left ITA resembles that of an open case which might increase the comfort of take-down for those who do not have a major experience with manual endoscopic ITA harvest. Other possible advantages are that identification of the LAD may be facilitated since the border between the right and left ventricle is better visualized. In addition the right coronary artery can be easily identified which makes the right side approach very promising for endoscopic double ITA grafting to the RCA and LAD. Although both pleuras were opened, one lung is deflated and CO2-insufflation was used, ventilatory problems were not encountered. For multivessel revascularization, a transabdominal, transdiaphragmatic approach may also be an alternative [20].
4.4. ITA take down
Harvesting of the ITA is best performed slowly using low energy cautery to allow for sufficient coagulation of side branches before cutting. This technique avoids clipping and numerous instrument changes. Smoke development is also minimized. After some adverse events in the beginning (side branch bleeding, one occlusion), ITA take down is now well standardized. In the plateau phase of the learning curve no more complications occurred. However, collisions can still occur the proximal and distal end of ITA harvest as the arms operate almost parallel to each other. It is important to alleviate any force felt by the operator at the console to minimize the risk of a sudden ‘spring’ effect while dissecting the ITA. It is also very important to maintain a high enough intrathoracic pressure as to provide as much working space between the anterior chest wall and the mediastinum as possible. In our experience an ITP up to 10 mmHg never caused significant hemodynamic impairment. This observation matches with the findings of Ohtsuka et al. who demonstrated that despite a significant increase of right heart filling pressures there was no change in heart rate, arterial pressure, or LVEF during prolonged elevated ITP with endoscopic ITA take-down [21]. According to their findings, high gasflow rates should be avoided unless needed for gas leakage.
4.5. Prevention of pedicle torsion
In one case torsion of the pedicle caused graft occlusion and required a minithoracotomy to allow reorientation and fixation. In his report on two successful TECAB procedures Loulmet [6] pointed out that twisting can occur when control of the pedicle is lost. Reorientation can be complicated given the limited field of view which hinders viewing the entire length of the ITA. To avoid this problem, the graft is now left in situ as long as possible. A stay suture at the anastomotic site is knotted to the epicardium close to the anastomotic site, so that when the graft is finally brought down, one hand can always hold onto the pedicle, while the other hand can guide the needle through. This way constant control of orientation is provided. It is also advisable to create a small pedicle with no excess fat or muscle tissue to minimize the risk of twisting by lung excursions. Exteriorization of the distal ITA through one of the ports as has been suggested in the past [6] is not recommended as it is a potential source for graft injury as well as a possible cause of graft torsion. Using the described in situ technique for distal ITA preparation exteriorization of the graft seems obsolete.
4.6. Identification of target vessel
In the beginning the pericardiotomy was made too lateral so that obtuse marginal or diagonal branches dominated the field of view. Due to the high magnification even a small diagonal branch can, and in fact was once in our series misleadingly be taken for the LAD. We now routinely open the pericardium as medial as possible which is usually at its mediastinal attachment. Then, a window is created that extends proximally until both the pulmonary artery and the left atrial appendage are in view. Following this line, the LAD is usually easily identified. In addition it is also helpful to watch for the different contraction patterns of the right and left ventricle to determine the course of the LAD. Once identified it is helpful to mark the target vessel by a clip to the surrounding tissue. After cardioplegia has been administered and the heart is decompressed the mediastinum shifts to the right changing the view. In addition, a different scope (30° angled down or 0°) might be used later during the procedure yielding a different perspective of the heart. By initially marking the target vessel, confusion caused by changing views can be avoided later.
4.7. Cardioplegia
Any type of cardioplegia may be used but we prefer the use of crystalloid cardioplegia because it enables constant flushing of the anastomotic site which helps to keep the surgical field bloodless, even in the event of back-bleeding. However, it is important to first identify the target vessel as one disadvantage of crystalloid cardioplegia is its low contrast.
4.8. Leakage from anastomosis
There are a number of techniques to perform an ideal anastomosis and it is beyond the scope of this article to suggest that the technique used here works best. The described technique to perform an endoscopic coronary anastomosis followed the intention to perform an: (1) open anastomosis with all stitches being visible; (2), stitching inside-out of the target vessel; and (3) avoiding any knots at the heel or toe of the anastomosis. Thus, the technique resembles the parachute technique used in open cases except for the fact that it is performed without assistance. In an experimental blinded study it was shown that the quality of these computer enhanced anastomosis was equal to those that were performed manually [7]. However, it became evident in this series that the technique has its drawbacks. In order to provide enough counter-traction during suturing at least one stay suture that approximates the pedicle to the site of the anastomosis is necessary. Nevertheless, the initial three stitches in the ITA are difficult because the pliable graft creates no friction for the needle. Sharper needles may help to solve this problem. It is of utmost importance to tighten the suture after every stitch in order to avoid leakage which we saw in two cases (one in group I and III, respectively). Once the anastomosis is finished, the heel is difficult to control endoscopically. In one TECAB case we had to perform a minithoracotomy due to the leakage from the heel of the anastomosis. We found it to be helpful to anchor the unused needle of the double armed suture remote from the anastomosis in the epicardium such that it creates some tension on the thread while suturing. Since not enough force feedback is provided to judge suture tension, visual clues (straightening of the suture, lifting of tissue) must be used to grade the amount of tension that is required without breaking the thread. This requires some experience and is best trained at the bench. Finally, before knot tying, the anastomosis should be inspected for loose loops. We have not observed leakage in the most recent cases.
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5. Conclusion |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionAppendix A. Conference...References |
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Footnotes |
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Appendix A. Conference discussion |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionAppendix A. Conference...References |
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Dr Falk: There is of course a lot of technologies that will change the way of surgery as we see it now, and I think clearly that there will be anastomotic devices that, especially in conjunction with robotic technology, may change the technique of doing anastomoses. Also I think that we might change the technique completely by adding some assistance to it. In the beginning we thought it was absolutely necessary to do this all by yourself, and of course it is very difficult to assist, but there will be ways that we can have additional assistance inside the chest, and that will improve also the times we have just shown.
Dr A. Moritz (Frankfurt, Germany): I have just one technical question. Besides all the problems you indicated, we also found that during dissection of the mammary you usually get very strict spasm of the vessel. Do you have any ideas how to overcome it, because if you have to sew on this small and spastic vessel, you are actually working on a virtually small structure that increases, and maybe some of the bleeding problems encountered in many institutions may be due to this spasm.
Dr Falk: I have to say that we have not seen so many spasms, and I think that clearly if you have a long enough pedicle it shouldn't be too much of a problem. However, it is of course true that you have only limited possibilities to manage everything, and if there is any doubt about the quality of graft, we would rather consider a conversion, which we have done in the past.
Dr S. Schueler (Dresden, Germany): The results pretty much match our experience, especially the IMA takedown time. I have seen on one of the pictures that you still use four incisions. Do you think it is necessary to use fourth one, because in the recent cases we have used three incisions?
Dr Falk: It is not absolutely necessary to have four incisions, and Diedier Loulmet has shown that previously, too, that you can do the procedure through three incisions only. We still feel very confident of having one additional port to hand in suture material, and I don't know if there is a really big difference between three or four ports. I would even add another port if I could get some assistance to the procedure. But you are, of course, right, you can do it through three ports only.
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References |
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TopAbstract1. Introduction2. Methods3. Results4. Discussion5. ConclusionAppendix A. Conference...References |
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