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Ann Thorac Surg 2000;70:839-843
© 2000 The Society of Thoracic Surgeons

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Original articles: cardiovascular

A comparison of robot-assisted versus manually constructed endoscopic coronary anastomosis

^a Division of Cardiothoracic Surgery, London Health Sciences Centre, University of Western Ontario, London, Ontario, Canada

Address reprint requests to Dr Boyd, London Health Sciences Centre, University Campus, 339 Windermere Rd, London, ON N6A 5A5, Canada
e-mail: douglas.boyd{at}lhsc.on.ca

Presented at the Thirty-sixth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 31–Feb 2, 2000.

	Abstract

Top Footnotes Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Background. New technology has enabled surgeons to attempt totally endoscopic coronary artery bypass grafting. Our purpose was to compare three different techniques of totally endoscopic anastomosis using a porcine animal model.

Methods. Porcine hearts were excised and the right coronary artery was dissected free for use as an arterial graft. The hearts were placed in a human thoracic model and an endoscopic arterial anastomosis between the free right coronary artery and the left anterior descending coronary artery was performed using one of the following: (1) two-dimensional visualization with straight endoscopic instruments (n = 8); (2) three-dimensional head-mounted visualization with curved endoscopic instruments (n = 7); or (3) three-dimensional visualization with robotic telemanipulation (n = 8). Pathologic analysis of suture placement, vessel trauma, and patency was performed. Anastomoses were graded according to quality, ease, and patency using a seven-point Likert scale (1 = excellent, 7 = very poor).

Results. Endoscopic anastomotic ease and quality were significantly improved when three-dimensional visualization and curved endoscopic instruments were employed. Telemanipulation enhanced the process and provided the best operative results with regard to time required to construct the anastomosis, as well as ease and quality.

Conclusions. Totally endoscopic anastomosis is feasible using currently available technology. Three-dimensional visualization and robotic telemanipulation significantly facilitate anastomosis construction and will likely benefit clinical operative outcome.

	Introduction

Top Footnotes Abstract Introduction Material and methods Results Comment Acknowledgments References

 
For the past few decades, surgical strategies for coronary revascularization have remained relatively static. The introduction of minimally invasive techniques has, however, brought cardiac surgical practice to the threshold of a revolution. Despite earlier widespread skepticism and controversy, numerous centers have already shown that minimally invasive coronary artery surgery can achieve similar results with less morbidity, more rapid recovery, and at a lower cost than "conventional" surgical revascularization [1]. As experience with video-assisted cardiac surgery has grown, more complex cardiac procedures are being investigated in both the laboratory and clinical arena. Significant technological advances have enabled a number of centers to perform endoscopic internal thoracic artery harvest and totally endoscopic coronary artery bypass [2, 3].

The list of challenges that surgeons face with endoscopic cardiac surgery is daunting. Such challenges include the instrumentation to control cardiac motion, visualization (both depth perception and optical resolution), limited working space, and limited surgical experience with endoscopic reconstructive techniques. In combination, these issues have, until recently, precluded the accurate and timely performance of endoscopically sutured anastomosis. To date, the rate-limiting step in accomplishing a totally endoscopic coronary artery bypass procedure has been the performance of an endoscopic anastomosis [4–6]. Until recently, endoscopic instruments lacked the necessary degrees of angulation required and were insufficiently long to achieve a precise microvascular anastomosis in the chest.

The clinical application of highly dextrous, telerobotic, on-line surgical work systems that can mimic human manipulative performance by providing up to 7 degrees of freedom under three-dimensional (3-D) vision has recently enabled several groups to successfully perform totally endoscopic coronary artery bypass. The purpose of this study was to investigate the ability of robotically assisted microsurgery under 3-D vision to facilitate the performance of video-directed coronary artery bypass in a cadaveric porcine heart model.

	Material and methods

Top Footnotes Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Three series of experiments were conducted comparing anastomosis performed with two-dimensional (2-D) visualization with conventional endoscopic instruments (n = 8), 3-D visualization with advanced endoscopic instruments (n = 7), and 3-D visualization with robotic telemanipulation (n = 8). Fresh abattoir-derived hearts were obtained from Yorkshire swine of either sex weighing 40 to 60 kg. The excised swine hearts were stored in normal saline solution, transported to the laboratory and prepared by excising the extraneous tissues surrounding the great vessels. The right coronary artery was identified and completely dissected free from its origin over a distance of 6 to 7 cm and used as the arterial conduit. The heart was then placed in a human thoracic model and oriented to reproduce the orientation of the in vivo human heart. The model used was a reproduction of the human rib cage covered with a layer of neoprene to simulate the soft tissues of the human thorax. All experiments were performed consecutively by the same surgeon who had endoscopically harvested more than 200 internal thoracic arteries.

In the first experiment, a 10-mm, 0-degree, 2-D endoscope (Karl Stortz, Tuttlingen, Germany) was placed through a port in the fifth intercostal space in the anterior axillary line. Conventional endoscopic instruments, needle driver, and forceps (Genzyme) were placed through ports in the fourth and sixth intercostal spaces in the midaxillary line. A robotic endoscopic positioner (AESOP 3000, Computer Motion, Goleta, CA) was used to control the endoscope. The right coronary artery was then anastomosed to the anterior descending coronary artery after a 3- to 4-mm arteriotomy had been performed. All anastomoses were performed end-to-side in a continuous fashion using 7-cm, 7-0 Prolene sutures (Ethicon, Inc, Somerville, NJ). In each case an intracorporeal instrument tie with five knots was made.

In the second series, the experiment was repeated using a 0-degree, 3-D endoscope (Zeiss, Oberkochen, Germany). The 3-D image was displayed on two monitors inside a head-mounted display (Vista Technologies Inc, Westborough, MA) and a 2-D image on a monitor above the control unit. Special curved endoscopic needle drivers (Scanlan, St Paul, MN) were used to perform the anastomosis.

In the third series, the Intuitive Robotic Microsurgical system (Intuitive Surgical, Mountain View, CA) was positioned and endoscopic slave instruments placed through port sites. The system consisted of a master console, a computer controller, and a three-arm surgical manipulator with fixed remote center kinematics. The surgical manipulators used had 3 degrees of freedom (pitch, yaw, and insertion), and exchangeable instruments added an additional 3 degrees of freedom, 2 degrees of freedom by means of a cable-driven mechanical wrist that allowed the end effectors to be articulated in all directions. Tool actuation (ie, grip) was programmable and provided an additional 1 degree of freedom. A master-slave motion scale of 3:1 was chosen in this study for all motions except roll. A 6-Hz motion filter built into the system eliminated unintended movements caused by tremor. For visualization, a custom 3-D videoscopic system that employed two three-chip cameras and 10x magnification was placed in the fifth intercostal space and positioned at a working distance of 6 to 7 cm from the target vessel. The end effectors served as combined needle holders/tissue graspers and were placed in the fourth and sixth interspaces in the midaxillary line. The right coronary artery was anastomosed to the AD coronary artery after a 4-mm arteriotomy was made. The anastomosis was performed remotely from the surgeon’s console using a 7-cm, 8-0 Prolene suture in a continuous fashion. An intracorporeal instrument tie was then made.

After completion of the anastomoses, the hearts were removed from the thoracic trainer and the anastomoses inspected visually at less than 10x laparoscopic magnification. Each anastomosis was checked for patency by passing a 2- to 4-mm probe through the arterial conduit into the anterior descending coronary artery and by visual (magnified) inspection. After transection of the anastomosis and fixation in 10% neutral buffered formalin, pathologic inspection was carried out for suture placement, evidence of trauma to the anastomotic site, and patency. The time required for the anastomosis was recorded. The quality and ease of the anastomosis were graded immediately after completion using a seven-point Likert scale (1 = excellent, 7 = very poor). Intraoperative events such as suture breakage, needle bending, and trauma to the graft or coronary artery were also recorded.

Results were compared among groups using analysis of variance with SAS version 6.12 statistical software (SAS Institute Inc, Cary, NC). Variables are presented as means ± standard deviations. A p value of less than 0.05 was declared statistically significant.

	Results

Top Footnotes Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Coronary anastomoses were completed successfully using each of the three techniques. There were substantial differences in technical ease, anastomotic quality, and anastomosis times among groups (Table 1). In all domains analyzed, 2-D visualization with traditional straight endoscopic instruments yielded the poorest operative outcomes. These anastomoses were extremely difficult to construct, and numerous intraoperative setbacks led to considerable surgeon dissatisfaction with this technique. Of the eight anastomoses constructed, two had significant endothelial damage, two had more than 50% stenosis, and suture breakage occurred while constructing two of the grafts. Overall quality was rated poor for these grafts, with a mean rating of 5.5 ± 0.9 (1 = best, 7 = worst).

Three-dimensional visualization combined with the Intuitive Robotic Microsurgical System (Intuitive Surgical, Mountain View, CA) allowed the easiest anastomosis construction, with a mean difficulty rating of 2.2 ± 0.5 (1 = best, 7 = worst). Mean anastomosis time was 14.8 ± 0.2 minutes per graft. Graft quality was rated highly at 1.6 ± 1.2 (1 = best, 7 = worst). Intraoperatively, two needles were bent and one suture was broken during knot tying. All anastomoses were widely patent.

	Comment

Top Footnotes Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Totally endoscopic coronary artery bypass is a procedure in evolution. Despite rapid advances in technology, thus far the rate-limiting step has been the performance of an endoscopic anastomosis [4, 6]. In this study, a computer-enhanced telemanipulation system successfully allowed the performance of a precise, totally endoscopic coronary anastomosis.

Cardiac surgeons have recognized the importance of achieving video dexterity and are adopting video-assisted techniques in increasing numbers [7]. In less than 2 years, major advances have been made with the adoption of robotic telemanipulation, computer enhancement, and the advent of true 3-D visualization.

In June 1998, Loulmet and colleagues performed the first clinical, totally endoscopic, computer-enhanced arrested heart coronary artery bypass in Paris [3]. A few months later, Reichenspurner and associates repeated this performance in Munich with the Zeus system (Computer Motion, Goleta, CA) [8]. In September 1999, our group successfully performed our first totally endoscopic beating heart bypass operation, also using the computer-enhanced Zeus microsurgcial system.

Although some investigators have pursued robotic telemanipulation technology, Lonn and colleagues, from Linkoping, and Verkkala and associates, from Helsinki, combined their efforts to perform the first clinical totally endoscopic anastomosis on the beating heart using conventional thoracoscopic instruments and the Vista 3-D visualization system (personal communication, Dr Kalervo Verkkala, Helsinki University Central Hospital, 1999). These investigators have highlighted the complexities of manual thoracoscopic anastomosis suturing and, as a result, are currently exploring alternative nonrobotic anastomotic strategies.

Despite widespread enthusiasm and acceptance of minimally invasive surgery, several limitations to progression to a totally endoscopic procedure have been identified. The first of these involves issues of visualization. Present endoscopic cameras offer reasonable resolution and magnification but do so in two dimensions. Experienced laparoscopic surgeons can compensate to an extent, but this involves a very long learning curve. The major difficulty with operating in 2-D is the difficulty in the performance of precise movements along the visual axis (z-axis). Recently, the introduction of 3-D endoscopes and head-mounted displays have promised to address this issue, but the initial "matchbox" camera configuration have not permitted easy port access. Early head-mounted display prototypes also lacked the resolution presently available in 2-D, three-chip camera systems. A new generation of 3-D systems promises to facilitate port access to the chest while permitting the chest to be insufflated with CO₂. Insufflation improves visualization by decreasing lung excursion into the working field and increasing the anterior/posterior working space, an essential factor when performing closed chest procedures. Geis [9] demonstrated the advantages of having both panoramic and close-up videoscopic views during closed chest videoscopic surgery. Panoramic views allow the movement and reorientation of surgical instruments into the surgical field with precision while lowering task time by as much as 16%. The location of the endoscope in relation to the anastomosis and instruments is critical to the success of an endoscopic procedure. A clear view of the anastomosis unobstructed by the working instruments is mandatory. The physical orientation and the optimal working angles between instruments, the anastomotic plane, and the angles of vision are important issues that must be considered when planning a closed chest approach. In telemanipulation procedures, the correct placement of ports ensures proper working angles and is necessary to prevent robotic arm impingement and interference.

Limitations of current endoscopic microvascular instrumentation include excessive length and inadequate degrees of freedom to permit optimal needle–tissue approach angles. Highly dextrous telerobotic manipulation systems have addressed a number of these limitations. Dexterity measurements of robotic systems have been described by Sturges and Wright [10], and are summarized by the following formula:

In this quantitative measure of dexterity, the natural frequency is dependent on the length. According to this model, dexterity can be increased by increasing either the resolution or the number of degrees of freedom of a robotic system. Theoretically, a robotic system with 7 degrees of freedom would have 1.8 times the dexterity of a system with only 4 degrees of freedom. Similarly, improving the resolution would increase the system dexterity at a given natural frequency.

The Intuitive system used in this study provided excellent resolution, depth perception, and magnification. The 7 degrees of freedom afforded by the articulating end-effectors allowed accurate and reproducible instrument to instrument transfer of 8-0 needles, and the high-resolution 3-D videoscopic system enabled precise anastomosis. A 6 Hz motion filter further enhanced precision by reducing tremor. The lack of haptic feedback did not seem to overly impede manipulation of tissues or 8-0 sutures. The loss of tactile input was largely compensated for by excellent resolution and visual cues. The average anastomotic time was only 14.8 minutes and included anastomoses performed during the "learning curve." This compares favorably to the average anastomotic time of 33 minutes previously reported using 2-D, and 15.7 minutes using 3-D, visualization and robotic telemanipulation with 4 degrees of freedom (Zeus, Computer Motion, Goleta, CA) in an animal model [8, 11, 12]. The benefits of 3-D visualization in facilitating coronary anastomosis using robotic telemanipulation was also demonstrated to apply to surgeons with varying amounts of endoscopic experience [12].

A critical issue, however, is how the different microsurgical systems will perform in human clinical cases. When operating on the beating heart, external anatomical limitations to robotic arm movement by the patients’ hips and arms and by stabilization hardware may influence the in vivo application of these systems. Variability in intrathoracic working space geometry, the size of the intercostal spaces, and the requirement for surgical assistance when operating on bleeding tissue could also potentially have impact on the clinical application of systems with larger robotic manipulators and end effectors. To date we have successfully performed eight totally endoscopic beating heart coronary bypass operations using the Zeus telerobotic system, demonstrating the clinical potential of this facilitating technology.

In summary, the findings of our study indicate that robotic telemanipulation and computer-enhanced devices will be more frequently applied as surgeons strive to minimize surgical incisions while maintaining operative dexterity and surgical accuracy.

	Acknowledgments

Top Footnotes Abstract Introduction Material and methods Results Comment Acknowledgments References

 
The authors thank Dr C. Guiraudon for providing pathologic analysis and Joan McLaughlin for her assistance with the project.

	Footnotes

Top Footnotes Abstract Introduction Material and methods Results Comment Acknowledgments References

 
This study was supported by Intuitive Surgical Inc, Mountain View, CA, and Medtronic of Canada, Toronto, Canada.

	References

Top Footnotes Abstract Introduction Material and methods Results Comment Acknowledgments References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Alan H. Menkis F. Neil McKenzie Richard J. Novick Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Boyd, W. D. Articles by Novick, R. J. Search for Related Content PubMed PubMed Citation Articles by Boyd, W. D. Articles by Novick, R. J. Related Collections Related Article