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Ann Thorac Surg 2001;72:1203-1209
© 2001 The Society of Thoracic Surgeons
a Division of Cardiothoracic Surgery, Department of Surgery, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA
Address reprint requests to Dr Chitwood, Department of Surgery, Division of Cardiothoracic Surgery, Brody School of Medicine, East Carolina University, 600 Moye Blvd, Greenville, NC 27858
e-mail: chitwoodw{at}mail.ecu.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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 TopFootnotes Abstract IntroductionMaterial and methodsResultsCommentDiscussionReferences |
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Methods. Consecutive patients with isolated mitral valve disease underwent either manually directed (n = 55) or voice-activated robotically directed (n = 72) video-assisted mitral operations. Cold blood cardioplegia, a transthoracic aortic clamp, a 5-mm endoscope, and a 5-cm minithoracotomy were used. This video-assisted minimally invasive mitral operation cohort was compared with a previous sternotomy-based mitral operation cohort (n = 100).
Results. Group demographics, New York Heart Association classification, and cardiac function were similar. Repairs were performed in 61.8% manually directed (n = 34), 75.0% robotically directed (n = 54), and 54% sternotomy-based (N = 54) mitral operations. The robotically directed technique showed a significant decrease in blood loss, ventilator time, and hospitalization compared with the sternotomy-based technique. Manually directed mitral operations compared with robotically directed mitral operations had decreased arrest times (128.0 ± 4.5 minutes compared with 90.0 ± 4.6 minutes; p < 0.001) and decreased perfusion times (173.0 ± 5.7 minutes compared with 144.0 ± 4.6 minutes; p < 0.001). In the minimally invasive mitral operation cohort, complications included reexploration for bleeding (2.4%; n = 3) and one stroke (0.8%), whereas the 30-day mortality was 2.3% (n = 3).
Conclusions. Video-assisted mitral surgery provides safe and effective results when compared with conventional sternal approaches. These positive results show a safe and stepwise evolution toward a totally endoscopic mitral valve operation.
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Introduction |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentDiscussionReferences |
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These criticisms forced minimally invasive valve operations to evolve along a slower tiered pathway based on surgeon comfort, incision size, and development of both new vision methods and instruments [9, 10]. The chal-lenge became to develop minimally invasive valve approaches with gold standard results that were reproducible among centers. Our current procedure has developed along a progressive pathway toward a completely endoscopic mitral operation, ultimately done by telemanipulation [9, 11]. This article focuses on our evolving experience in video-assisted minimally invasive mitral surgery (VMIMS).
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Material and methods |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentDiscussionReferences |
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A 
2 analysis of all categorical data were performed to determine statistical significance. Also a one-way analysis of variance was conducted on all quantitative data, and posthoc comparisons were applied using Tukey’s Honestly Significant Difference to create pair-wise group comparisons. A rank transform was applied before statistical analysis to control for lack of variance homogeneity with ventilator hours. Data are shown as mean ± standard error of the mean. An analysis of variance was applied to the consecutive cohorts to determine any significant difference between cohorts.
Operative approaches for VMIMS have been altered slightly from our earliest descriptions [9, 11]. Patients were intubated for single left-sided ventilation to facilitate exposure before commencing cardiopulmonary bypass. A transesophageal echocardiographic probe was positioned for preoperative, intraoperative, and postoperative evaluation of ventricular function; adequacy of cardiac chamber de-airing; and mitral valve function. Patient positioning and incision placement are depicted in Figure 1.
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A transthoracic aortic cross clamp (Scanlan International, Inc, Minneapolis, MN) was inserted through a 4-mm incision in the midaxillary third intercostal space. The clamp was positioned under close video-assisted control to avoid vascular injury and to ensure complete occlusion. In 109 patients (85.8%), antegrade cardioplegia was given intermittently through an aortic root catheter. Retrograde cardioplegia was used alone in 2 patients (1.6%), whereas 4 patients (3.2%) had combined antegrade and retrograde infusions. Cardioplegia was redosed routinely (500 mL at 4°C) at 20-minute intervals. In 12 patients (9.4%), cold ventricular fibrillatory arrest was used. During cardiac arrest, systemic perfusion was maintained between 26°C and 28°C.
The left atrium was entered through a 4-cm incision in Waterston’s interatrial groove [12]. For valve exposure, a Heartport retractor (Heartport, Inc, Redwood City, CA) was placed across the chest wall through the anterior fourth interspace near the right sternal border (Fig 2). A 5-mm, two-dimensional (0° or 30° view) thoracoscope (Linvatec, Inc, Largo, FL) was inserted through the fourth or fifth intercostal space, parallel to the superior pulmonary vein (Fig 1). In the 55 manually directed (MD) patients, an assistant, directed by the surgeon, manipulated the camera. For the 72 robotically directed (RD) patients, the voice-activated AESOP 3000 system (Computer Motion, Inc, Santa Barbara, CA) was attached to the thoracoscope, and the surgeon commanded camera movements. In each operation the majority of the valve procedure was performed using assisted vision through the thoracoscope. Long-shafted instruments, passed through the incision, allowed tissue removal and remodeling, suture placement, chordal transfers and replacements, annuloplasty ring implantation, and knot tying. Direct vision was used for retractor placement and atriotomy closure.
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Results |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentDiscussionReferences |
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All three cohorts had similar intensive care unit lengths of stay (p = not significant). However, length of stay from operative procedure to discharge was significantly less in the RD and MD cohorts compared with conventional cohorts (p < 0.001).
Follow-up of patients undergoing minimally invasive mitral valve operations was 90.0% (114 of 127). Mean follow-up was 25.1 ± 3.6 months. At 6 weeks, 1 mitral valve repair patient developed a moderate leak. This patient has been closely followed and is scheduled for repeat transesophageal echocardiogram. Ninety-seven patients (85.1%) reported no symptoms, and 9 patients (7.9%) experienced occasional New York Heart Association functional class II symptoms. Five patients (5.1%) improved, but returned with New York Heart Association functional class III symptoms. These 5 patients had reoperative valve replacements. Of these 5 patients, 2 patients had an anterior ring dehiscence at 38 and 53 months, and 1 patient required replacement at a different institution. The remaining 2 patients were dialysis-dependent renal failure patients that required replacements at 1 and 2 months, secondary to bacterial endocarditis.
The 30-day operative mortality was 2.3% (3 of 127). There was 1 patient death from pneumonia on postoperative day 28 and 2 patient deaths at home on postoperative days 15 and 29 from arrhythmias. The overall mortality at follow-up from the minimally invasive mitral valve operation patients was 4.7% (6 of 127). There were no in-hospital deaths. The remaining 3 patient deaths were nonvalve related at 40, 42, and 50 months. One in-hospital death (1%) occurred in the sternotomy group from a cardiac arrest.
Perioperative complications are shown for all groups in Table 4. There were two conversions to sternotomy for bleeding. One patient sustained a left atrial appendage injury with the cross clamp and the other an aortic injury from a transthoracic aortic cannula. Three neurologic complications occurred in the minimally invasive mitral valve operation group: a transient brachial plexus injury, a permanent stroke, and transient ataxia. In the sternotomy cohort, two transient strokes and one permanent stroke occurred. In the minimally invasive mitral valve operation group, 3 patients required reoperation for bleeding from noncardiac sources, whereas 7 sternotomy patients required reexploration. In all the minimally invasive mitral valve operation reexplorations, the bleeding was controlled through the thoracotomy incision without the need for extension. Early in the series, a right hemidiaphragm paralysis led to our only patient with prolonged ventilatory requirements postoperatively (32 days). Thirteen patients in the sternotomy group had prolonged ventilation (> 48 hours). Although no quantitative pain metrics were obtained, the 11 patients who already had prior sternotomies for cardiac surgery reported less pain from their minithoracotomy incision and returned to regular activity more rapidly.
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Comment |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentDiscussionReferences |
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Loulmet and colleagues [15] suggested a serial progression toward a totally endoscopic, minimally invasive cardiac operation with graded levels of exposure and reliance on video-assistance. Many surgeons have used modified sternal approaches and altered perfusion techniques to affect safe, direct-vision minimal access mitral valve operations [1, 2,]. At East Carolina University, we have moved serially from using direct-vision smaller incisions for mitral operations (Level I) to assistant-held video-assistance (Level II), to video-directed, voice-activated robotic techniques (Level III), and recently, to robotic mitral valve repairs using the da Vinci system (Intuitive Surgical, Inc, Mountain View, CA) (Level IV). For safety and best results, we suggest tiered progression in relying on video assistance and smaller incisions.
The series herein describes the clinical results in our first 127 VMIMS done between June 1996 and November 2000. Approximately half the operations were facilitated by voice-activated robotic camera control. Peripheral cardiopulmonary perfusion, antegrade aortic root cardioplegia, transthoracic aortic clamping, a 5-cm incision, and video-assistance were the mainstays of operative technique. Vanerman and colleagues and Mohr and colleagues [4, 6] have reported excellent results using combined video-assisted and balloon Endoclamp (Heartport, Inc, Redwood City, CA) aortic occlusion. In our series, we selected the transthoracic clamp for aortic occlusion because of positional stability, ease of use, safety, and decreased cost. Our notions were supported by results showing no clamp dislodgements, no aortic injuries, and a single clamp-related complication (0.8%).
Our patients have done well, as reflected by less bleeding, ventilator time, and overall hospital length of stay, compared with a sternotomy cohort. This decrement in ventilator time and length of stay suggests patients have less respiratory limitation and less recuperative time after a minimally invasive approach.
After we embraced robotic camera direction, we were able to provide similar arrest times to the sternotomy group as well as provide decreased perfusion times. The consecutive series was evaluated in five cohorts comparing serial cross-clamp and perfusion times. With the addition of Aesop and increased experience, significant decrement in these measurements occurred. Figure 3 depicts the mean cross-clamp and perfusion times for each cohort. A learning curve between 50 to 75 cases is suggested by a p less than 0.01, starting between groups 1 and 3. Furthermore, a p less than 0.05 between groups 2 and 4 may suggest acquired benefit from the addition of Aesop. It was impossible to separate whether these decreases were related to robotic camera control or progressive facility with a thoracoscope approach. However, surgeon control and operative ease were enhanced markedly by voice-activated robotic manipulation.
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Footnotes |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentDiscussionReferences |
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Discussion |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentDiscussionReferences |
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They are reporting on a consecutive series of 127 patients who underwent video-assisted mitral valve repair through a right minithoracotomy. During the first 55 patients, the camera was directed manually, and subsequently voice-controlled, robotically driven. In our own series in the same time period, we have operated on more than 400 patients, and the first 200 was port access and the latter 200 with Randy Chitwood’s techniques. The interesting observation is that we did see a learning curve during the first 60 patients, and then we had a major improvement. It was also interesting to look at the results of the individual surgeons; it varied between 2.2% for the experienced to 3.7% all over.
Looking at your results, I have to raise the following questions. The improvements of your results have been influenced by two things. I think the one thing is, of course, the surgeon’s learning curve, and also the implementation of the robotic-assisted, camera-guiding system. How many cases would you expect for an individual surgeon to overcome the learning curve?
Reading your manuscript, it is obvious that your follow-up is not complete; you only have 61 patients in follow-up. Do you have any information about the missing patients? I think this is critical because there is some discussion whether minimally invasive techniques provide the same long-term quality as open surgery provides.
Complex repairs are deemed to be too difficult through a minimally invasive approach. I think one of your videos clearly showed that you have learned how to handle the complex repairs, but could you mention if there is any exclusion criteria where you would decide from the very beginning for an open technique?
In your manuscript, you also mentioned that you operated on 12 patients with ventricular fibrillation and hypothermia. I assume these were patients who underwent a reoperation. In our series, an incidence of 12.6% of patients underwent reoperations, and this patient cohort clearly benefitted from minimally invasive approaches. Could you comment on these data?
Finally, I would like to ask you about your interest in computer-enhanced mitral valve surgery, which was mentioned at the very end. What do you really think and what is your driving force to introduce such a complex technique in difficult mitral valve repair operations?
I would like to thank President Matloff and the Society for inviting me to comment on this paper. Thank you very much.
DR KEVIN D. ACCOLA (Orlando, FL): I appreciate your fine results, as we have been following Dr Chitwood’s work for some time now with regard to this technique. I raise the question regarding your length of stay because you emphasize that as one of your key points that you felt was significant. It still seems to this day that our length of stay through median sternotomy mitral valve procedures is still dictated by arrhythmias and inability to anticoagulate a patient. I wanted to ask if you do anything different postoperatively and if you indeed see less atrial fibrillation or fewer complications with anticoagulation with regard to these patients, as this is still a determining factor in our patients’ length of stay. Thank you.
DR HERMANN REICHENSPURNER (Munich, Germany): I also would like to congratulate the group around Dr Chitwood for these excellent results. We did a comparative study in Munich, Germany that was presented last year at the European Association for Cardiothoracic Surgery. We compared 60 patients that were operated on using the Port Access approach, which means using aortic balloon occlusion compared to the direct transthoracic clamping that was used in 30 patients. This clamp, as you know, was developed by Dr Chitwood and his group, and we found a significant decrease both in cardiopulmonary bypass time as well as in cross-clamp time when using the transthoracic clamp. Also intermittent ventricular fibrillation occurred less in the direct cross-clamp group.
Now, looking at the manuscript, I see that despite the fact that you are doing quite a number of complex repairs, the relation of repairs on the anterior leaflet is less compared to repairs on the posterior leaflet. So would you think that still complex repairs on the anterior leaflet will be rather an indication for an open mitral valve repair? Thank you very much.
DR FELGER: I appreciate the comments of Drs Mohr, Reichenspurner, and Accola.
First, I would like to address Dr Mohr’s comments about the learning curve. Looking at the data, the cross-clamp times and bypass times decreased incrementally after the first 55 cases as facility was gained with the transthoracic approach. Also, the voice-activated robotic assistance added benefit by decreasing camera manipulation and cleaning.
Our follow-up is limited to 61% of the patients. Living in East Carolina, as rural as it is, a lot of immigration in and out of the area occurs. Furthermore, some patients are referred from other states for the minimally invasive approach. We are continuing to pursue follow-up and will update it for the final manuscript.
Both Dr Mohr and Dr Reichenspurner comment on exclusion criteria for this approach. We have performed ten repairs of the anterior leaflet as our comfort with this approach has increased. As one’s comfort level increases, one can address more complex valve repairs. Other exclusion criteria were previous right thoracotomy, chest wall radiation, increased body mass index and excessive axillary adipose tissue. Also, patients who needed concomitant revascularization were excluded.
Dr Mohr, you were correct in assuming the cases done with ventricular fibrillation were reoperations.
At East Carolina University, computer-assisted minimally invasive mitral valve repair with the current telemanipulator systems has been a major focus.
We have just completed the first FDA mitral repair trial of 17 mitral repairs using the da Vinci system. At this time, the FDA has approved a new Phase II multi-center trial that will be commencing this month.
Dr Accola, the atrial fibrillation rate averaged 22% between all three groups. The robotically driven cases had 18% atrial fibrillation, whereas the manually driven ones had 26%. Each patient was either converted medically prior to discharge or the rate was controlled and anticoagulation therapy was started. The sternotomy patients were treated in the same manner.
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References |
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