Ann Thorac Surg 2005;79:S2248-S2253
© 2005 The Society of Thoracic Surgeons
Supplement
Current Status of Endoscopic and Robotic Mitral Valve Surgery
W. Randolph Chitwood, Jr, MD, FACS*
Division of Cardiothoracic and Vascular Surgery, Eastern Carolina Cardiovascular Institute, University Health Systems, East Carolina University, Greenville, North Carolina
Accepted for publication February 21, 2005.
* Address reprint requests to Dr Chitwood, Division of Cardiothoracic and Vascular Surgery, Department of Surgery, East Carolina University School of Medicine, Moye Blvd, Greenville, NC 27858 (E-mail: chitwoodw{at}mail.ecu.edu).
Presented at the 4th Annual Lillehei Heart Institute Symposium Celebrating the 50th Anniversary of Open-Heart Surgery by Cross Circulation, Minneapolis, MN, Oct 19–20, 2004.
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Abstract
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Doctor C. Walton Lillehei and his colleagues set a standard for innovation and new technology development in cardiac surgery. Robotic mitral valve surgery has taken a similar translational course proffered by Lillehei. We evaluated 341 video-assisted and 100 da Vinci robotic mitral repairs done at East Carolina University between 1996 and 2004. The 30-day mortality was 2.2% and 1% for the video-assisted and robotic series, respectively. Complex anterior and posterior leaflet repairs were performed in both cohorts. Repair results were excellent. For the da Vinci group there was a clear learning curve, with repair, perfusion, and aortic cross-clamp times falling significantly (p < 0.05). This reports suggests that robotic and endoscopic minimally invasive mitral surgery could evolve to become the standard of care.
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Introduction
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Scientific wealth tends to accumulate according to the law of compound interest. Every addition to knowledge of the properties of matter supplies "[the physical scientist]" with new instrumental means for discovering and interpreting phenomena of nature, which in their turn afford foundations of fresh generalisations, bringing gains of permanent value into the great storehouse of "[natural]" philosophy.
—Lord Kelvin
Although there has been a recent drive toward new technology development in cardiac surgery, designed to address the challenges of our changing specialty, innovation certainly is not new to us. Doctor C. Walton Lillehei and his colleagues at the University of Minnesota typified the best in surgical innovation and intervened at a time when open cardiac surgery was on the brink of failure [1]. His times were not unlike ours in which the value of heart surgery was and is again questioned. Generally, scientific advancements reap compound interest as suggested above by Lord Kelvin. However, great discoveries also can raise questions and eclipse further advancements. By 1953 Dr John Gibbon had developed and used the cardiopulmonary bypass pump successfully; however, his and others’ early elation was subdued by deaths in later patients [2]. No doubt, the work of Lillehei, Cohn, DeWall, Varco, and Warden, among others at the University of Minnesota between 1954 and 1958, provided the seminal bridge for open heart surgery until reliable perfusion and cardiac pacing systems were developed (Figs 1, 2) [1, 3, 4]. Cross circulation and the DeWall bubble oxygenator resulted from a close look at the problems Gibbon had encountered [1, 5]. Clearly, their curiosity originated in the operating room, but clinical problems were defined and solved in the laboratory, before being translated back to patients to alleviate the original challenge. From their successes they taught other surgeons how to perform reliable cardiac surgery. The technology spread rapidly to other centers. Figure 3 shows Drs Will Sealy and Glen Young using a DeWall bubble oxygenator and Sigma motor "finger pump" at Duke University in 1958.
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Fig 1. Doctor C. Walton Lillehei (1954) in front of a display showing how his innovative cross circulation, incorporating a "biologic oxygenator," was used to perform early congenital heart operations 50 years earlier.
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Fig 3. An early cardiac operation at Duke University. Doctors Will Sealy and Glen Young are using the DeWall helical bubble oxygenator and "finger" pump in 1957 to perform a cardiac operation. They added the "Brown" heat exchanger to the circuit.
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Our quest for new methods to perform endoscopic cardiac surgery has mirrored the Lillehei translational approach. Just as in general surgery, cardiac surgery patients now are benefitting from minimally invasive and endoscopic approaches. However, the fixed paraboloid thorax interjects more ergonomic restriction than that posed by the relatively elastic abdominal wall. This report describes the iterative approach that we have taken to develop robot-assisted endoscopic mitral valve surgery. Our working hypothesis has been that complex mitral repair surgery can be done endoscopically, using either pure video-assistance or a surgical robot, and with results that are similar to traditional operations.
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Material and Methods
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Since 1997 we have used two approaches to perform endoscopic mitral valve repair surgery: video-assisted controlled by a voice-activated camera arm and by robotic telemanipulation and three-dimensional endoscopy [6–8]. Each of these operations was done by a single surgeon and multiple assistants. Tables 1 and 2 show the methods used to perform our video-assisted mitral valve repairs. For these operations peripheral arterial and venous cannulation, kinetic venous drainage, thin-walled high-flow cannulas, a 5-cm right minithoracotomy, and a newly developed transthoracic aortic clamp were used. A voice-activated robotic (AESOP3000) arm (Intuitive Surgical, Inc, Sunnyvale, CA) and a two-dimensional endoscopic camera either assisted with vision in difficult mitral access areas or was the sole image source during completely endoscopic repairs (Fig 4) [7]. We developed long-shafted instruments to access the mitral plane and subvalvular area through the small incision. These devices included the transthoracic aortic clamp, a mechanized knot pusher, combination tip forceps, and a suture cutter. In repair patients either a Carpentier Physio or Cosgrove annuloplasty band was used (Edwards Lifesciences Inc, Irvine, CA). For valve replacements either an Edwards Perimount tissue or St. Jude mechanical prosthesis (St. Jude Medical, Minneapolis, MN) was used. Figure 5 shows a mitral valve with severe bileaflet prolapse being repaired through a 5-cm incision using video-assistance. In this group, chordal replacements and transfers, sliding plasties, Alfieri plasties, leaflet resections, bileaflet repairs, complex annuloplasties, and valve replacements were done.
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Fig 4. The surgeon is shown directing a voice-activated robotic camera and repairing a mitral valve through a 5-cm minithoracotomy using long endoscopic instruments and assisted vision.
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Fig 5. A two-dimensional image of an endoscopic complex mitral repair. Chordae tendineae have been transferred from P2 of the posterior leaflet to the mid-anterior leaflet at A2 to reduce anterior leaflet prolapse in a Barlow’s valve. P1 will be approximated to P3 using a leaflet-reducing sliding plasty. (Carpentier Classification.)
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Additionally, since May of 2000 we have performed more than 100 mitral repairs robotically using the da Vinci Surgical System (Intuitive Surgical, Inc). With the exception of the incision being reduced to 4 cm, the same positioning, perfusion, and exposure techniques, shown in Tables 1 and 2, were used (Fig 6) [8, 9]. Table 3 describes the placement of each robotic element, including the three-dimensional camera and two instrument arms (Figs 7, 8). This system provides telemanipulation of microinstruments with greater than 7 degrees of operative freedom at the annular plane and subvalvular region. In these operations the entire repair was done endoscopically with the surgeon operating from a console placed 10 feet from both the patient and assistant surgeon. There were no valve replacements in this series of robotic repairs. The Cosgrove annuloplasty band was used in each patient for annular reduction. In the first 50 patients 2–0 braided sutures were used, and in the last 50 patients nitinol Coalescent U-Clips (Medtronic, Inc, Minneapolis, MN) were used to fasten the annuloplasty band. For sufficient compression, required for annular reduction in sliding plasties, braided 2–0 suture was preferred. This da Vinci repair cohort included chordal replacements and transfers, sliding plasties, Alfieri plasties, leaflet resections, bileaflet repairs, and complex annuloplasties (Fig 9).
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Fig 6. The operating surgeon is positioned at a console and remains immersed in the operative landscape via the three-dimensional camera. He or she is telemanipulating mitral valve tissues using various instrument tips, each having a full range of motion. The patient-side assistant is responsible for instrument exchanges as well as suture delivery and needle retrieval. The assistant currently relies on two-dimensional images for operative reference.
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Fig 7. The 1-cm robotic instrument arms are placed through the chest wall as described in Table 3. A transthoracic retractor arm elevates the interatrial septum toward the sternum. The three-dimensional camera is placed through the 4-cm incision, which will serve also as a working port for the assistant.
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Fig 9. Robotic mitral repair: (A) P1 is the most anterior or lateral posterior leaflet scallop and P2 is the redundant mid-scallop that is being resected. (Ant. Leaflet = anterior mitral leaflet.) (B) P1, P2, and P3 of the posterior leaflet are shown. P2 will be resected. P3 has been elevated radially from the mitral annulus and will be displaced toward P2 for the sliding plasty. (AC= anterior commissure; PC = posterior commissure; * = left fibrous trigone.)
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Learning curve metrics were recorded and calculated for perfusion, cross-clamp, leaflet repair, annuloplasty band placement, and total repair times. Mean data are represented along with standard error of the mean and standard deviation (SD) values, and statistical differences in learning curve metrics were determined by the paired Student’s t test, with significant differences shown at p less than 0.05.
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Results
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Mitral Valve Surgery: Video-Assisted
In the 341 video-assisted mitral operations performed between January 1999 and November 2004, repairs were done in 73% and replacements were done in 27%. The mean patient age for this group was 60.4 ± 0.8 (SD ± 14.9) years. Cardiopulmonary bypass and aortic cross-clamp times averaged 139.7 ± 2.7 (SD ± 51.1) and 86.8 ± 2.4 (SD ± 43.4) minutes, respectively. From the incision to skin closure, operating times averaged 4.35 ± 0.80 (SD ± 1.6) hours. Of this group 4.4% (n = 15) required reexploration for bleeding, and 29.6% (n = 101) received a blood product transfusion. In this group of patients there were 8 (2.2%) deaths (<30 days). The average length of hospital stay was 6.5 ± 0.5 (SD ± 9.2) days. No cardiopulmonary perfusion complications developed. Of the 249 video-assisted repairs 6 patients or 2.4% have required a reoperation.
Mitral Valve Repairs: Robotic Using da Vinci
Between May 2000 and September 2004, 100 mitral repairs were done with the da Vinci robotic surgical system. The first 40 patients represented those done under US Food and Drug Administration-guided clinical trials, and repairs were restricted to posterior leaflet and annular disease. In the first 45 patients the annuloplasty was done using sutures, and in the last 55 nitinol clips were used to secure the annuloplasty band. There were no valve replacements in this group, and the average patient age was 57 ± 0.2 (SD ± 12.0) years. Cardiopulmonary bypass and aortic cross-clamp times averaged 162 ± 4.2 (SD ± 37.2) and 126.0 ± 3.0 (SD ± 31.8) minutes, respectively. From the incision to skin closure, operating times averaged 4.72 ± 0.10 (SD ± 0.90) hours. Of this group 2.0% (n = 2) required reexploration for bleeding, and only 15% (n = 15) received a blood product transfusion. There was 1 (1.0%) death (<30 days) and one 6 weeks after surgery for an overall hospital mortality of 2%. In this group 2 patients required a reoperation for a failed valve repair. One of the reoperative patients had a stroke at the second operation and constituted one of the early mortalities. The other death was related to respiratory failure and bowel ischemia. The average length of hospital stay was 4.8 ± 0.8 (SD ± 3.8) days.
To evaluate the learning curve times, data from the first 50 da Vinci patients were compared with the second group. Significant decreases were seen in both perfusion (174 to 150 minutes, p < 0.004) and aortic cross-clamp times (138 to 114 minutes, p < 0.003), respectively. Also, leaflet repair (40 to 32 minutes, p = 0.02), annuloplasty band placement (49 to 34 minutes, p < 0.005), and total robot operative times (84 to 66 minutes, p < 0.001) were reduced significantly in the latter group. Interestingly, the number of sutures placed increased from 9.4 to 11.2 (p < 0.005) in the presence of decreasing operative times and increasing repair complexity.
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Comment
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To perform the ideal cardiac valve operation surgeons must operate in restricted spaces through tiny incisions, which demand new operative methods including assisted vision and advanced instrumentation. Since 1996 minimally invasive valve surgery has evolved in an iterative fashion. Carpentier and Loulmet [10] provided a nomenclature for these operations that spanned direct vision with a modified sternal incision to a completely closed chest robotic operation. This progression is akin to a Mount Everest ascent where each climber starts from a base camp of knowledge and operative comfort but must ascend through new territory, stopping to acclimatize before moving ahead.
Despite early reservations by many surgeons that mitral operations done through small incisions would render inferior results and be unsafe, several large series from pioneer surgeons demonstrated safety and efficacy with less invasive mitral valve operations. Between 1996 and 2002, Cosgrove (as reported in Chitwood and Nifong [11]) had performed 1,427 minimally invasive mitral operations, using direct vision, an upper hemisternotomy, and modified perfusion methods. This series had an impressive mortality (0.3%) and complication rate (bleeding [3.1%], strokes [1.8 %], and respiratory insufficiency [0.8%]). Complex repairs were done in times similar to conventional surgery, and the repair results were excellent [11]. Between 1996 and 2002 Cohn (as reported in Chitwood and Nifong [11]) had done 411 minimally invasive mitral valve operations. His operative mortality was 0.2% with no deaths in the repair group, and his operative results were excellent. Bleeding, strokes, and myocardial infarctions occurred in 2%, 2.2%, and 1.0% of patients, respectively [11]. Grossi and colleagues [12] then compared 100 conventional mitral repairs with 100 Port-access (Cardiovations, Summerville, NJ) repairs done through a right minithoracotomy. They found that valve repair quality was similar with fewer complications. These and other large series assured surgeons that a minimally invasive surgery would be part of the future for mitral operations.
Since 1996 Mohr and associates [13, 14] have repaired successfully more than 1,000 mitral valves using videoscopic methods. They first reported excellent results using the AESOP robotic arm and long instruments. In these patients aortic cross-clamp and perfusion times were similar to their conventional operations, and the operative mortality was 1.2%. We began to perform video-assisted mitral repairs in 1996 and reported our first 127 cases in 2001 [15]. Of these, AESOP was used to direct the camera in 72 operations. Throughout the early series, we performed ever more complex operations with commensurate decreasing operative times. The operative and 30-day mortalities for this series were 0.4% and 1.7%, respectively. Repairs included quadrangular resections, sliding plasties, chord replacement or repair, and Alfieri plasties. Anterior leaflet disease was avoided in these initial cases. Robotic camera-arm direction enabled less lens cleaning and shorter cross-clamp times.
The AESOP video-assisted method became our operation of choice for all mitral repairs until the da Vinci system became available in 2000. It still is our preferred method for mitral valve replacements and reoperations for mitral disease. The 341 patients reported herein include bileaflet and anterior leaflet repairs, complex posterior leaflet repairs, lone annuloplasties, replacements, and reoperations. The operative mortality (2.2%) is similar to our sternotomy patients as we have not selected patients for the video-assisted operations. No deaths were related to perfusion complications or valvular repair failures. In our first 38 reoperations using this method, we had 5.7% mortality, which was similar to a cohort of conventional mitral reoperations [16]. As in first-operation patients, blood product transfusion, intubation times, and hospital stay were reduced using the video-assisted approach compared with a 100-patient conventional cohort.
In May 1998, using an early prototype of the da Vinci articulated "microwrist," Carpentier and colleagues [17] performed the first true robotic mitral valve repair. In May 2000, our group performed the first mitral repair in the North America using da Vinci [18]. We then conducted both a US Food and Drug Administration Phase 1 Safety and Efficacy study and a Phase 2 Multicenter (10 centers) Robotic Mitral Repair Trial, which eventuated in US Food and Drug Administration approval for the procedure. Of the 112 patients in this trial, follow-up transthoracic echocardiograms at 1 month after surgery showed that 103 patients (92.0%) had either no or grade 1 regurgitation [19]. At East Carolina University our first 38 da Vinci mitral repair patients were reported in 2003 [20]. In these patients no more than trace mitral regurgitation existed 3 months after surgery. Data from the first 100 patients reported in this paper suggest that we are continuing to maintain a low operative mortality, quality repairs, reduced transfusions, and less hospitalization than our sternotomy patients. Although we did not attempt to quantitate quality of life or return to normal activities, it has been obvious to us that faster recovery occurs using both methods compared with our sternotomy patients. We have been impressed that with experience the operative times have fallen significantly in nearly every metric studied. Moreover, at the same time we have been able to increase the complexity of repairs. Bileaflet repairs are done routinely.
To summarize, Dr Lillehei set a standard for surgical innovation and showed modern surgeons that we must be the masters of our fate. Robotic and endoscopic surgery clearly has a long way to go to convince all surgeons and their patients that telemanipulation is the best method of accessing and repairing intracardiac structures. Not unlike cross circulation, what we have today is probably the bridge to operations that will provide more accuracy, better vision, tactile feedback, and greater surgeon comfort. Surgeons should look to past innovators and pioneers, not to copy but to study how they solved puzzles through translation of a clinical problem to the laboratory and back. To be sure, the trajectory is unknown; however, part of these telemanipulation methods and robotic devices will be a part of the armamentarium for future surgeons.
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Fig 2. Doctors Richard DeWall and Lillehei developed the helical bubble oxygenator, improving on the Gibbon device, and first used in patients in 1955. Here Dr DeWall is demonstrating his invention at the 2004 Lillehei symposium nearly 50 years after the innovative first use. (Photograph by Dr Chitwood.)
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Fig 8. In a robotic mitral repair, ports with right and left instrument arms are shown as described in Table 3. The aortic clamp is placed posterior and slightly cephalad to the left arm, and the three-dimensional camera is inserted through the 4-cm working incision, which is the only access for the assistant surgeon.
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References
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- Gibbon JH. Application of a mechanical heart and lung apparatus to cardiac surgery Minn Med 1954;37:171-180.[Medline]
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- Chitwood WR, Elbeery JR, Chapman WHH, et al. Videoassisted minimally invasive mitral valve surgerythe "micro-mitral" operation. J Thorac Cardiovasc Surg 1997;113:413-414.[Free Full Text]
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Abstract
Introduction
