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Ann Thorac Surg 2001;72:1263-1269
© 2001 The Society of Thoracic Surgeons
a Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, Missouri, USA
b Department of Cardiothoracic Surgery, Sarasota Memorial Hospital, Sarasota, Florida, USA
c Department of Cardiothoracic Surgery, Medical City Dallas Hospital, Dallas, Texas, USA
Address reprint requests to Dr Damiano, Division of Cardiac Surgery, Washington University School of Medicine, Campus Box 8234, Suite 3108, Queeny Tower, One Barnes-Jewish Hospital Plaza, St. Louis, MO 63110
e-mail: damianor{at}msnotes.wustl.edu
Presented at the Thirty-seventh Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 29–31, 2001.
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Abstract |
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Methods. Thirty-two patients scheduled for elective primary coronary surgery underwent endoscopic anastomosis of the left internal thoracic artery (LITA) to the left anterior descending (LAD) artery. Three thoracic ports (two for instruments and one for a camera) were placed, and a robotic system was used to perform the LITA–LAD graft. Conventional techniques were used to perform the other grafts. Thirty-one patients underwent median sternotomy and 1 patient underwent a limited anterior thoracotomy.
Results. Graft flow was measured in the operating room and averaged 37 ± 19 mL/min. Mean anastomosis time was 24 ± 9 minutes. There were three intraoperative revisions (9%). Two were for inadequate flow and one for an inadvertent injury. Each of these grafts was successfully revised by hand. There were no technical failures of the robotic system. Average postoperative length of stay was 5.5 ± 2.7 days. There were three reoperations for bleeding, but none of these were related to the LAD anastomosis. Two months following the operation, selective angiography revealed a graft patency of 93%. The patients have been followed for 16 ± 4 months.
Conclusions. This initial prospective multicenter trial documents the feasibility of robotically-assisted coronary bypass grafting. Further trials are warranted to establish the safety and efficacy of this new technology.
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Introduction |
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The Zeus Robotic Surgical System (Computer Motion, Inc, Goleta, CA) was used in this trial. This system has been previously described in detail [6] The principal difference between robotically-assisted and traditional surgery is that a computer is integrated between the instrument handle and instrument tip. This digital interface overcomes many of the problems associated with traditional endoscopic surgery. The computer software is able to manipulate the digital movement with both filtering and motion scaling. The filtering eliminates fine tremor. The motion scaling allows the surgeon to make easy-to-perform gross movements at the surgeon console and have those movements translated into a microscopic scale inside the patient. This has been shown to facilitate endoscopic suturing [6].
Prior to beginning clinical studies, the Zeus System was used extensively in both cadavers and live animals [8, 9]. Coronary artery anastomoses were successfully performed in a chronic animal model, with 100% patency at 1 month [8]. The system was first used clinically for coronary artery bypass grafting by Dr Reichenspurner’s group in Munich with good success [10]. This multicenter prospective clinical trial was approved by the Food and Drug Administration to evaluate the safety and efficacy of robotically-assisted ECABG. The three centers involved in this trial were: Hershey Medical Center, Hershey, PA: Medical City of Dallas, Dallas, TX; and Sarasota Memorial Hospital, Sarasota, FL. All patients enrolled in this trial underwent robotically-assisted anastomosis of the left internal thoracic artery (LITA) to the left anterior descending (LAD) coronary artery. All other grafts were sewn by hand in the traditional fashion. Since this was the first clinical trial of endoscopic coronary bypass grafting, it was mandated that the procedures be performed under what was considered optimal conditions, on the stopped heart with cardiopulmonary bypass and cardioplegic arrest. The primary study end-points were graft patency at 8 weeks and the incidence of device-related complications. All patients were followed continuously with primary end-points being major adverse cardiac events and recurrent angina.
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Material and methods |
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Operative approach
After induction of general anesthesia, the three robotic arms were attached to the operating room table. The patient and robotic arms were prepped and draped in a sterile fashion. In the majority of patients, a standard median sternotomy was performed and the LITA was taken down in the traditional manner. The pericardium was opened and the heart was exposed. The patients were fully heparinized. The ascending aorta and right atrial appendage were cannulated, and cardiopulmonary bypass was established. The patient underwent routine myocardial protection techniques.
In 1 patient, the LITA was harvested thoracoscopically through three endoscopic ports. The camera port was placed in the fourth intercostal space in the anterior axillary line, and the two instrument ports were in the second and sixth intercostal spaces in the midaxillary line. A small (4 cm) anterior thoracotomy was made in the third intercostal space. The patient was placed on cardiopulmonary bypass with the Heartport system (Heartport, Inc, Redwood City, CA).
Robotic system setup
The Zeus robotic arms were used to manipulate modified endoscopic instruments (Karl Storz, Culver City, CA). The arms were attached directly to the operating table. The surgeon controlled these arms by manipulating specially designed handles at the console. The handles allowed for four full ranges of motion (pan, roll, tilt, and in or out), as well as grasping. The surgeon’s motions were directly and precisely translated from the console to the robotic arms by a computer controller. Custom-designed software allowed for tremor elimination, as well as motion scaling over a range of 2:1 to 10:1.
Three thorascopic ports were used, two for the robotic arms and one for the camera. This port placement was determined from previous animal and cadaveric experiments, and has been previously described [11]. In the majority of cases, 5-mm ports were used. A 0-degree endoscope (Karl Storz) was used and attached to a three-chip video camera (Tricam SL, Karl Storz) and light source (Zenon 300, Karl Storz). A two-dimensional endoscope was manipulated with the Aesop voice-controlled robotic arm. A two-dimensional video image was monitored by the surgeon at the console and by an assistant on a 21-inch monitor at the head of the operating room table (Fig. 1). Specialized instruments were inserted into the ports.
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Robotically-assisted anastomosis
The heart was left in situ. The chest retractor was relaxed to allow for a more normal anatomic position of the chest wall. An arteriotomy was made in the distal LAD. The distal LITA was prepared manually for anastomosis. A continuous end-to-side anastomosis was performed endoscopically with the robotic instruments. No manipulation of the heart was necessary to perform the anastomosis, and there was ample visualization of each stitch (Fig. 2). In most cases, an assistant held the LITA pedicle through the chest incision with standard instruments. The running anastomosis was performed with a specially designed 7-cm double-armed 7-0 polytetrafluoroethylene (Gore-Tex, W. L. Gore & Assoc, Flagstaff, AZ) suture. Motion scaling was used for each anastomosis.
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Intraoperative graft flow
Blood flow through the LITA graft was measured with ultrasonic flow probes and a flowmeter (HT311, Transonic Systems, Inc, Ithaca, NY). If the flow was judged not to be adequate (flow < 10 mL/min, poor diastolic augmentation), selective coronary angiography was performed in the operating room suite.
Patient follow-up
During the postoperative period, all hemodynamic parameters, chest tube drainage, and the need for inotropic support were carefully tabulated. The length of intensive care unit and hospital stay was recorded for each patient. Eight to 10 weeks after the operation, patients underwent a coronary angiogram of the LITA to LAD anastomosis to assess graft patency. These angiograms were read by an independent core lab and graded. Only 1 patient who had a robotically sewn anastomosis was not available for angiographic follow-up. At late follow-up (16.0 ± 4.4 months), patients were contacted by phone and interviewed regarding their medical condition. A one-page questionnaire was used to inquire about recurrent cardiac symptoms or the occurrence of major adverse cardiac events. Of the 32 patients, 30 were available for follow-up (94%).
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Results |
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1.5 mm). One patient was excluded because of an innominate vein injury and subsequent hemodynamic instability, and 1 patient had contamination of the camera. This left a total of 32 patients who underwent an endoscopic robotically-assisted anastomosis. The enrollment by center was 19 patients at Hershey Medical Center, 9 patients at Sarasota Memorial Hospital, and 4 patients at Medical City of Dallas.
Patient demographics
Of the 32 patients, there were 24 men and 8 women. Their mean age was 63 ± 9 years. Their preoperative ejection fraction averaged 54% ± 12%.
Intraoperative results
Each of the operating room staffs were able to assemble the robotic system expeditiously. The average set up time was 16 ± 8 minutes. There were no intraoperative complications related to the placement of the robotic ports. The robotic system functioned without fail in all 32 procedures. There were no intraoperative device-related complications.
The average number of grafts performed per patient was 2.8 ± 1.0. Mean cross-clamp time was 54 ± 15 minutes. The time required to perform the robotically-assisted LITA–LAD anastomosis was 24 ± 9 minutes (range 15 to 43 minutes).
All patients underwent intraoperative ultrasonic determination of flow through the LITA–LAD graft. Thirty of the grafts had adequate flow with diastolic augmentation (94%). The average graft flow was 37 ± 19 ml/min.
There were three intraoperative graft revisions. Two grafts had inadequate flow and were taken down and reconstructed manually. In 1 of the cases, an intraoperative angiogram was performed. The entire LITA was unable to be visualized. The distal anastomosis was widely probe patent. A tentative diagnosis of graft spasm was made. In the 2nd case, angiography was not available. A subsequent review of the videotape revealed a technical error. In the 3rd case, an intraoperative revision was required due to the misplacement of an internal thoracic artery pedicle tacking suture. Conversion to the manual technique was easily accomplished in each case, and each of these patients left the operating room with what was judged to be a patent LITA–LAD anastomosis.
Postoperative course
There were several postoperative complications. Three patients required a return to the operating room the evening of surgery for excessive mediastinal hemorrhage. In each case, the bleeding was not related to the robotically-assisted anastomosis. One source of bleeding was the lateral trocar instrument insertion site. The bleeding was stopped successfully in all patients, and each went on to have an uneventful recovery.
Three patients had postoperative atrial fibrillation. All patients returned to sinus rhythm with medical therapy.
There were no other complications during the postoperative period. The average length of stay in the intensive care unit was 1.3 ± 1.0 days. The average hospital stay was 5.5 ± 2.7 days.
Intermediate follow-up
Eight to 12 weeks after operation, graft patency was assessed by selective coronary angiography. These studies were performed at the institution where the patient underwent surgery. All angiograms were evaluated and read by an independent core laboratory. Of the patients who underwent successful robotic anastomoses, only 1 patient was not available for angiographic follow-up. Twenty-six of 28 grafts were patent (93%). Two grafts were occluded. One of these patients was asymptomatic and has had no further reinterventions. The other patient underwent a redo coronary artery bypass graft procedure. The native LAD in these 2 patients measured 1.2 and 1.69 mm. All other grafts had thrombolysis in myocardial infarction (TIMI) 3 flow. In these grafts, there was one significant stenosis (> 50%).
If one considers the one intraoperative occlusion, the overall graft patency was 27 of 30 (90%), with a nonrestrictive patency rate of 26 of 30 (87%).
Late follow-up
Thirty of 32 patients (94%) were available for late follow-up. The mean followup was 16 ± 4 months. Twenty-eight of 30 (93%) patients were doing well, with no recurrent angina or major adverse cardiac events. There were no instances of myocardial infarction. Two patients had follow-up catheterizations not in the protocol. One patient developed angina and had a negative cardiac catheterization with no evidence of graft stenosis. One patient developed angina, had a cardiac catheterization that showed a distal LITA anastomosis lesion, and underwent angioplasty with stent placement. This was the same patient who had a stenosis on the follow-up angiogram.
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Comment |
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The intraoperative results with the robotic system were acceptable. The robotic system was able to be set up quickly and without difficulty. The mean anastomotic time in this early experience in the hands of numerous surgeons was 24 minutes. While this is approximately twice as long as a conventional anastomosis, it is within reasonable limits, and was not felt to endanger the patient. It was estimated that the use of robotics added between 30 to 45 minutes to the length of the procedure, considering the set up and the extra anastomotic time. Clearly, a totally endoscopic procedure would add a significantly longer amount of time. The added time of these procedures should be considered when recommending them to a particular patient.
While this study demonstrates the feasibility of endoscopic coronary bypass grafting, the question of efficacy remains unanswered. The graft patency rate was 93%. Two patients required reintervention for graft stenosis of occlusion during the 1st year of follow-up. It is reassuring that at two of the three sites in this study, graft patency was 100%, and there were no reoperations or major cardiac adverse events. Two of the graft occlusions occurred in patients with small left anterior descending coronary arteries. This suggests that in the early phase of this new technology, patients need to be carefully selected for these procedures. Without haptic feedback and three-dimensional vision in this robotic system, there may not be enough safety margin in patients with small native vessels. The results also emphasize the importance of surgical training. The precise learning curve for robotic coronary surgery remains to be defined. We are presently recommending 80 to 100 hours of training before proceeding with clinical cases. This should include work in an inanimate trainer, live animals, and cadavers.
The safety and reliability of the robotic system was also documented in this small trial. There were no device failures and no device-related complications. It is important to view this work in perspective. Handheld endoscopic anastomoses have proven to be difficult, if not impossible. This study underlines the advantages of robotics in endoscopic microsurgery, and is an example of how computers can be used to enhance surgical dexterity. By translating the surgeon’s operative motions into a digital format, it is possible to remove tremor by filtering high frequency signals. The use of motion scaling allows the surgeon to make large, easy-to-perform movements at the console and have these translated into a microscopic scale inside the patient. In addition, the nonintuitive motion of endoscopic instruments was able to be eliminated with computer software, since the instrument handle and tip are no longer attached to each other.
There are also significant advantages in visualization. The voice-controlled robotic arm that holds the endoscopic camera had the advantage of maintaining a stable image when compared to traditional manually held cameras. This also allowed the camera to remain under the direct control of the surgeon. Moreover, greater magnification can be obtained with endoscopic cameras. The magnification of 12- to 15-fold achieved in these procedures was significantly greater than the two- to three-fold magnification that is traditionally used in cardiac surgery. All of these features of the robotic microsurgical system combine to help enable the surgeon to perform endoscopic coronary anastomoses.
The 1-year follow-up in these patients is gratifying. Twenty-eight of 30 (93%) patients were doing well with no recurrent angina or major adverse cardiac events. There were no late graft occlusions. Clearly, long-term follow-up is needed before any conclusions can be drawn regarding the efficacy of this procedure. However, the short-term results clearly justify further investigation of this new technology.
There are many limitations to this study. First of all, it represents a small cohort of highly selected patients. No conclusions can be drawn regarding the efficacy of this procedure. Large scale multicenter prospective clinical trials will be needed to determine the value of robotically-assisted endoscopic coronary artery bypass.
Even in this highly selected group, there were eight intraoperative exclusions (18%), mainly due to a small or diseased target vessel. It would be expected that as confidence with this technique increases, the procedure may become more widely applicable.
The study also did not represent a completely endoscopic approach. Most of the patients had a sternotomy to allow manual performance of other bypass grafts. However, this report does establish that the most difficult part of the procedure, the coronary anastomosis, can be performed endoscopically with robotic assistance. However, there are many challenges that need to be overcome to perform a completely endoscopic CABG. Some of these include proper port placement, overcoming the tight space limitations of the closed chest, and the difficulty of exposure and identification of target vessels.
The experience of others around the world with robotically-assisted surgery supports the findings of this study. The large experience in Europe by Dr Mohr’s group at the University of Leipzig [12] and Dr Schueler’s group in Dresden [13] with robotically-assisted endoscopic coronary bypass grafting has been very positive. The Dresden group has recently reported 26 patients who underwent totally endoscopic coronary bypass grafting. Seven of these were done on cardiopulmonary bypass on the arrested heart, and 19 on the beating heart. Their initial results have been positive. They have shown that it was possible to harvest the LITA and complete a LITA to LAD graft with excellent short-term results. Dr Boyd in London, Ontario, has also recently reported a series of 15 patients undergoing totally endoscopic coronary bypass grafting on the beating heart with 100% patency [14]. These early results with robotic systems suggest that a completely endoscopic approach to CABG is feasible in carefully selected patients. While it is our belief that patient morbidity will be reduced with this type of approach, randomized prospective multicenter trials are clearly needed to prove this hypothesis.
This report represents a first step on the journey to a truly minimally invasive coronary artery bypass graft procedure. The early results with this technology are encouraging, and further clinical trials are warranted. Although progress has been made, there are still many hurdles to be overcome to develop a reproducible, technically straightforward, and widely applicable endoscopic coronary artery bypass grafting procedure. New technology may be needed to streamline and shorten operating times. A major challenge will be the treatment of patients with multivessel disease. Image guidance systems and devices that enable anastomoses may play a critical role in this area. Finally, the introduction of haptic feedback and three-dimensional visualization may improve the operative results.
In summary, this initial multicenter clinical experience supports the hypothesis that robotic assistance is an enabling technology that allows for the performance of endoscopic coronary anastomoses. Further clinical trials are warranted to explore the potential of this new technology and establish its precise role in the treatment of patients with coronary artery disease.
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Discussion |
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Recently, Boyd in Canada, as well as groups in Leipzig, Frankfurt, and Dresden, have been working toward a totally endoscopic coronary operation in patients. Similar patency rates have been achieved there using both arrested heart robotic and beating heart robotic methods. However, to date, these series are very small. Their work and this presentation have highlighted both the promise and the difficulty of these methods. This work also very nicely shows that we are working in the right direction but have many mountains to climb. Midterm patency rate is somewhat lower than traditional ITA anastomoses, visualization imperfect, haptic input absent, and longer times are required for suturing. Moreover, others have shown that multisite grafting is still difficult, especially in the circumflex coronary region. Similarly, even in beating heart nonrobotic coronary surgery, we have not been able to graft as many vessels as in traditional arrested heart sternotomy patients. Doctor Damiano has nicely outlined in his manuscript the future positives as well as the weaknesses of the study, as well as the technique in general. Clearly, there is a need for a larger series from multiple investigators.
The pioneering step taken is meritorious as it previews part of the future, and that is, computer-assisted micromanipulation near the surgical plane and at the anastomotic site. With evolving parallel technology, including articulated robotic wrists, distal anastomotic clips and devices, proximal anastomotic conduit delivery systems, and new micro cardiopulmonary bypass pumps, as well as bio-glues, as well as greater definition of three-dimensional imaging and surgical "GPS-like" navigation systems, to think less than positive I believe skepticizes the Wright Brothers’ original intuition. However, we have much to do to realize Dr Damiano’s and others’ dreams and visions.
Doctor Damiano, I would appreciate it if you would comment on the ideal robotic device if you could have your wish. Both of the currently available devices have advantages and disadvantages. Could you compare currently available surgical robotic technology? We have recently completed the first FDA trial using the da Vinci system for mitral valve repair surgery at our institution and have done 17 cases. Topographically exact trocar placement for robotic arm placement with respect to specific cardiac sites was difficult in our patients. When you begin closed chest ITA harvest in multiple anastomoses, how do you plan to solve this problem? What are the solutions for the future?
Lastly, for multiple closed chest anastomoses, how do you propose to manipulate the heart to reach the circumflex vessels, as we rarely are referred single- and double-vessel disease today? Also, would you comment on using these robotic devices for a totally endoscopic coronary artery bypass operation with regard to closed chest beating heart versus empty beating hearts with micro cardiopulmonary bypass pumps versus cardioplegically arrested heart methodology, and the benefits of each?
Again, I thank the Society for a truly outstanding meeting and the opportunity to discuss this paper.
DR DAMIANO: I thank Dr Chitwood for his kind remarks, and also to recognize his pioneering work in this field and in driving this technology forward. He has asked many questions, and I will try to answer them in order.
The first is what would be the ideal robotic device. Neither of the devices presently on the market achieve all of what we would hope to have eventually in a robotic system. We need a device that is easy to use, quick to set up, and requires a short learning curve. I think that ideally these systems would have haptic feedback, which right now we do not have. 3-D Visualization would also be beneficial, as long as it can be achieved with the resolution of two-dimensional cameras.
I am beginning to think also we may need to look at reengineering these robotic devices. One of the most difficult aspects of this surgery is the fact that the instruments are rigid rods. Particularly in closed chest approaches, trying to maneuver these rigid instruments around the chest is difficult and puts a premium on port placement. Perhaps we will be able to develop flexible cameras and instruments in the future. With the recent advances in nanotechnology, maybe small robotic platforms will someday be put inside the chest. I think the ideal system would also have, as Dr Chitwood has suggested, the capability for image integration that we could use both for intraoperative guidance and for port placement and target localization, and also for consultation (eg, cineangiography, echocardiograms).
There is certainly a great deal of challenging work for engineers before we get to the ideal system, but I think it is important to point out that both the systems presently on the market have enabled totally endoscopic coronary bypass grafting. They do provide for a significant enhancement of surgical dexterity. I think there is an extremely bright future in this area as the systems become less expensive and easier to use.
In terms of the advantages and disadvantages of the two systems presently available, the Computer Motion system and the Intuitive Surgical system, I think both basically consist of the same three components.
The advantages of the Intuitive system include its micro wrist articulation, though the Computer Motion system will soon have that available. The Intuitive system also includes 3-D visualization. While one can use the Storz 3-D system with the Computer Motion system, it is not integrated into the system that was used in this trial.
The advantages of the Computer Motion system are that the instruments can be custom-made and can replicate exactly what you use during a traditional open coronary bypass grafting. I should acknowledge both Scanlan and Storz for making most of the endoscopic instruments that we used in this trial. The instruments have a cost similar to traditional instruments. This is an area of high cost in the Intuitive system because of the micro wrist articulation.
I think the Computer Motion system also has the advantage of being able to be flexible in its use. All of the arms are independent as opposed to the Intuitive system where all three arms are attached to each other. This allows for an ease of use. I also think this will be important as this technology is introduced since it will allow you to evolve your use of the robotic system. Initially, you may want to use the system for part of the procedure and perhaps use it just for a mammary takedown or maybe doing a single anastomosis, as in this trial. As you get more and more experience and you are further along in your learning curve, then you can advance to the real challenge of closed chest, completely endoscopic, beating heart coronary bypass grafting.
In summary, I think both systems have certainly their advantages and disadvantages. Both enable surgeons to perform endoscopic bypass grafting.
In terms of closed chest bypass grafting and port placement, I think this is a tremendous challenge for the whole field. The anastomosis is really not that difficult. Once you are at that point, the anastomosis is actually the easy part of the operation. The hard part is trying to determine where your ports should be, and also the many different steps involved in exposing the coronary artery for bypass grafting. In the future, we probably will use some type of preoperative imaging studies, coupled with computer guidance to precisely determine the appropriate port placement for each vessel. This would be a great help.
You asked about the challenges of multivessel grafting. No one around the work has achieved anything more than one or two grafts. The Dresden group has done some double-vessel bypass grafting in very, very selected patients. However, getting to the circumflex and posterior descending systems is going to be a tremendous challenge. I think we will need better retractors, and different operating room tables that will let us really rotate the patient. You mentioned the idea of using partial bypass or other techniques to provide more space within the chest. When you look at the incredible selectivity of these patients undergoing endoscopic CABG, clearly there is a significant group of patients, because of their chest wall anatomy and the fully beating heart, in which there is just not enough room to perform the surgery. We may have to put those patients on bypass, or use right ventricular assist, or go back to the early days when we were using the Heartport system and perhaps complete cardioplegic arrest. Finally, I think there is a great future for anastomotic devices, new instrumentation, and computer guidance to enable multivessel grafting. I thank the Society for allowing me to present this study.
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