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Ann Thorac Surg 2000;69:1176-1181
© 2000 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, University Hospital Grosshadern, Ludwig-Maximilians University, Munich, Germany
Address reprint requests to Dr Reichenspurner, Department of Cardiac Surgery, University Hospital Grosshadern, Marchioninistr 15, D-81377 Munich, Germany
e-mail: hcr{at}hch.med.uni-muenchen.de
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Abstract |
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 Top Abstract IntroductionPatients and methodsResultsCommentReferences |
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Methods. Port-Access mitral valve replacement or repair (PAMVR) was undertaken using an endovascular cardiopulmonary bypass (CPB) system. Fifty patients underwent Port-Access mitral valve replacement or repair. A three-dimensional thoracoscope was inserted allowing complete three-dimensional projection of the mitral valve (Vista). In the last 20 patients, the camera was attached to a robotic arm (Aesop), which allowed stabilization and voice-activated movement of the camera. Mitral valve repair was performed in 26 patients, and the valve was replaced in 24 patients with a mechanical valve prosthesis.
Results. Median time of operation was 4.2 hours, aortic cross-clamp time 83 minutes, CPB time 125 minutes, intensive care unit stay 1.5 days and hospitalization 9.0 days. Three months follow-up was complete in 40 patients, with 34 patients (85%) in New York Heart Association class I and 6 patients in class II. Mortality was 0% and rate of reoperation was 2%, with a follow-up time up to 1.5 years postoperatively.
Conclusions. Using three-dimensional video and robotic assistance, it was possible to minimize the length of skin incision, but at the same time to optimally visualize the whole mitral valve apparatus in order to perform true Port-Access mitral valve operation, including various repair techniques.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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The Port-Access technique uses an endovascular cardiopulmonary bypass (CPB) system, in combination with a small thoracic access, which was developed at Stanford University [4]. After extensive experimental studies [5, 6], the first clinical programms on Port-Access mitral valve operation in humans started in 1996 at various centers [7–9].
This article focuses on our total experience of Port-Access mitral valve operation, and describes the importance of three-dimensional video-assistance using a three-dimensional intrathoracic mini-camera, which projects into a head mounted display. In the last 20 cases, a voice-cotrolled robotic arm was used to hold and position the camera.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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Preoperatively, 58 patients underwent assessment of the abdominal aortic, iliac, and femoral arteries using Doppler-sonography. Evidence of a major peripheral vascular disease served as a contraindication for the use of the endovascular CPB system. In addition, transesophageal echocardiography (TEE) was performed in all 58 patients to study the mitral valve disease. The condition and diameter of the ascending and descending aorta were evaluated. A severely atherosclerotic aorta and a diameter of more than 4 cm, as well as a moderate or major aortic valve incompetence, served as contraindications to the procedure. A total of 8 patients were excluded from a minimally-invasive approach due to the above mentioned reasons.
The endovascular CPB system used consists of a Y-shaped femoral arterial return cannula, a femoral venous cannula for drainage of the right atrium, an endopulmonary vent catheter inserted to the right internal jugular vein, and an endoaortic balloon occlusion catheter (Endoclamp; Heartport Inc, Redwood City, CA).
After the induction of anesthesia, the left and right radial arteries were used for invasive blood pressure monitoring to detect partial or total occlusion of the brachiocephalic trunk by the endoaortic balloon.
The patient was placed in a supine position, with the right shoulder elevated about 30 degrees. At operation, a small (4 to 7 cm) right submammary incision was performed and the fourth intercostal space was entered. A soft tissue retractor (Heartport Inc) was used to open the intercostal space and to retract the subcutaneous tissue and underlying musculature.
A 15-mm thoracic port was inserted posteriorly and cranially of the thoracic incision to insert the three-dimensional endoscopic mini-camera (Vista Cardiothoracic Systems Inc, Westborough, MA). The camera holder was then attached to the voice-controlled robotic arm (Aesop, Computer Motion Inc, Goleta, CA) for camera guidance. The robotic arm was mounted onto the operating table, adjacent to the left shoulder of the patient, and reached over the patient’s chest to hold the camera (Fig 1).
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Venous drainage was augmented by a centrifugal pump connected to the heart-lung machine. After initiation of CPB, the heart was electrically fibrillated to allow for correct placement of the endoaortic balloon, which was inflated about 2 cm above the aortic valve, as monitored by TEE. A balloon pressure above 300 mm Hg was usually associated with complete occlusion of the aorta. Any residual flow, beside the balloon, was monitored and detected by Doppler or TEE. After full occlusion, antegrade blood cardioplegia was administered.
The left atrium was incised above the origin of the right upper pulmonary vein as is done in regular mitral valve operation. The three-dimensional camera was positioned in the chest so that the whole mitral valve apparatus was visible on the screen. The mitral valve was then carefully assessed and evaluated with regard to potential reconstructive operation.
The robotic camera arm held the camera in a stable position and was guided using voice control. In addition, several preset positions could be programmed, to which the robot would automatically return after the appropriate command. The microphone was attached to the helmet, which allowed three-dimensional display of the videoscopic image (Fig 2). The surgeon was then able to see the operative site through the incision, or the endoscopic picture inside the helmet, without having to move his head. Thus, some parts of the operation are done under direct vision, and others using the endoscope. The endoscopic picture has proven to be very helpful particularly in examining the subvalvular apparatus and checking sufficient knot tying.
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In case of mitral valve replacement, the anterior leaflet was removed first and the posterior leaflet was kept in place. The valve was then measured and replaced by a mechanical valve prosthesis using interrupted annular valve sutures.
After the procedure, a left ventricular vent catheter was inserted through the valve and the left atrium was closed using a running suture. Before the suture was tied, careful retrograde deairing was done through the atrium, using a venting catheter. In addition, the ascending aorta was punctured with a small needle, proximally to the inflated balloon. Ventricular and atrial pacing wires were inserted, and after 30 minutes of reperfusion patients were weaned from CPB and the femoral cannulas were removed. All patients had intraoperative TEE control to assess the result of mitral valve reconstruction and to detect any paravalvular leak after mitral valve replacement. After hemostasis, the skin incisions were closed (Fig 3).
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The intraoperative data were compared to a cohort of 49 patients who underwent conventional mitral valve operation during the same time period. There were no significant differences with regard to age (median 63.5 years), sex (33 women, 16 men), left ventricular ejection fraction (median 52%) or preoperative diagnosis.
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Results |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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The median values for total operative time, duration of CPB, duration of aortic occlusion, duration of ventilation, length of intensive care unit stay and hospitalization are listed in Table 1. All patients were weaned from CPB without major inotropic support in stable hemodynamic condition. During operation, no major complication occurred, and in particular no arterial or aortic injury.
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All patients had intraoperative TEE control of the operative result. After valve replacement, no paravalvular leak was seen. After valve reconstruction (n = 26), only 1 patient had a mitral insufficiency grade II after anterior leaflet repair, all other patients had no or minimal (up to grade 1) regurgitation.
The echocardiogram was repeated at time of discharge in all patients (Table 2). One patient showed a minor paravalvular leak (grade I) post replacement. After mitral valve repair there was no mitral regurgitation in 22 patients, grade I regurgitation in 3 patients, and 1 patient with a grade II reflux. Forty-six patients had only minor or no complaints of postoperative pain, and 4 patients reported moderate postoperative pain. The rate of new onset of atrial fibrillation was less (8%), compared to those in the conventionally operated mitral valve group (28%, p = not significant).
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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There are major differences with regard to the method of CPB. While after ministernotomy or parasternal incision, conventional cannulation can be used, minithoracotomies are most often combined with femoral cannulation. For the latter method, specific transthoracic aortic clamps have been developed, as well as the endovascular balloon occlusion technique of the ascending aorta as part of the Port-Access system [3, 4]. The present report concentrates on 50 consecutive patients, in which the mitral valve was operated on using the Port-Access technique, in combination with a right anterior minithoracotomy. The mortality in the series was 0%, 1 patient had to be reoperated on 3 months after mitral valve repair of the anterior leaflet; this patient had a conventional mitral valve replacement with an uneventful postoperative recovery. Although there was a trend towards a longer total operation time, CPB time, and duration of aortic cross-clamping in the Port-Access mitral valve replacement or repair cases compared to conventional mitral valve operation, the recovery of the patient was faster resulting in a slightly earlier postoperative discharge. Of course, prospective randomized studies would be desirable to draw definite conclusions.
In order to minimize the length of skin incision to about 5 cm on average, videoscopic assistance was found to be absolutely essential. A three-dimensional system with a head-mounted display was chosen for better depth perception to allow mitral valve repairs. The head-mounted display allows direct vision of the surgical field through surgical loops as well as a view of the three-dimensional videoscreen without movement of the head. The first assistant was also wearing a helmet, which facilitated his help. Other displays, such as electrocardiogram monitor, fluoroscopy image, and TEE could be displayed as well, either alternatively or in addition to the endoscopic pictures.
In the last 20 patients, the three-dimensional camera was attached to a voice-controlled robotic arm. This arm allowed correct stabilization of the camera, and either incremental or continuous movement of the camera was controlled by the surgeons voice. As an additional advantage, two firm positions to which the arm would relocate could be programmed, according to the surgeon’s preference. This facilitated the use of the videoscopic camera during the operative procedures and shortened time of operation. Optimal visualization of the mitral valve is essential, since direct view of the mitral valve and the subvalvular apparatus is not always possible through limited incisions. Despite this improved visualization, optimal exposure of the mitral valve is not always possible. This does not influence the quality of a mitral valve replacement or a repair of the posterior mitral leaflet including an annuloplasty-ring insertion. This might limit, however, the feasibility of complex repairs of the anterior leaflet, including difficult reconstructions of the subvalvular apparatus, such as chordae shortening or transposition. In our series, the only case requiring reoperation was a patient with an isolated anterior leaflet prolapse. In our current practice, patients who require complex reconstruction of the anterior leaflet still undergo conventional mitral valve repair.
The complications observed consisted of minor wound healing complications in the groin and postoperative hemorrhage, requiring operative revisions in 3 patients. The bleeding sites of these patients were either thoracic ports or intercostal vessels. Careful videoscopic inspection of the wound and all thoracic ports are extremely necessary before wound closure. In 1 patient, a right ventricular perforation was observed, probably caused by the endopulmonary vent catheter. With insertion of a 30-degree endoscope, it was possible to directly suture the defect. No femoral, iliac, or aortic artery injury occurred in any of the patients. However, all patients underwent preoperative screening of their iliac and femoral arteries to exclude patients with evidence of peripheral vascular disease. One patient had evidence of a minor paravalvular leak after mitral valve replacement that did not require reoperation.
Aortic balloon migration was not a serious problem among our patients. The balloon position was carefully monitored by TEE and was corrected if necessary [10].
A comparable series of minimally invasive Port-Access mitral valve operations reporting on 51 patients, was published by Mohr and colleagues. In this series, a more lateral minithoracotomy was chosen as surgical access. Hospital mortality was 9.8%, with 2 cases of retrograde aortic dissection. Three patients required reoperation for paravalvular leakage [8]. Another series derives from New York University, where 130 patients were operated using the less invasive Port-Access technique for mitral valve disease. The results and complications in the series were acceptable and comparable to the results presented in our study, however using a slightly larger skin incision most likely due to the absence of video-assistance [7]. As stated by Edward Verrier in his editorial on minimally invasive Port-Access mitral valve operation, experience in patient selection will be critical to obtaining excellent results [11]. When we started the Port-Access mitral valve program at the University of Munich in May 1997, only 20% of all patients referred for mitral valve operation were chosen for the Port-Access technique. With increasing experience and confidence in this new surgical technique, 80% of all referred patients are operated on using this less invasive access. Major contraindications at this moment are evidence of major peripheral vascular disease, as documented by preoperative Doppler-sonography, severely calcified mitral valve anulus, and necessary complex reconstruction of the anterior leaflet.
A different technique, using the same minithoracotomy access, the so-called micromitral valve operation, has been described by Chitwood and colleagues [3]. In their series, the authors emphasize the necessity for video-assistance to allow accurate exposure of the mitral valve through the limited access. The only difference in their surgical technique lies in the fact that direct transthoracic aortic cross-clamping was applied using a specifically designed transthoracic aortic clamp. Both techniques seem to be equally safe. There is a potential danger of pulmonary artery injury in direct transthoracic clamping, as compared to the potential danger of retrograde aortic dissection using the endoaortic balloon occlusion catheter. Apart from this technical difference, the results in the series published by Chitwood are excellent, and compare favorably with conventional mitral valve operation and our results of Port-Access mitral valve repair or replacement.
In another series, published by Loulmet and associates, different surgical methods were compared for less invasive mitral valve operation. Twelve patients underwent a minithoracotomy compared to 10 patients who were operated on through a ministernotomy. The series consisted of 19 mitral valve repairs and 2 replacements. In 2 cases it was necessary to convert to a larger incision. Mortality was 0% and the patients were discharged with normal valve function. When comparing the minithoracotomy and ministernotomy, the authors were in favor of the small sternotomy approach for better exposure of the valve [12]. As a potential disadvantage, the parasternal or ministernotomy approach may require division of the left atrial root and interatrial septum with possible postoperative arrhythmias. The minithoracotomy allows for well-known entry through the interatrial groove into the left atrium and a direct access to the mitral valve.
The three-dimensional video and robot-assisted Port-Access technique can be recommended for isolated mitral valve operation. Evidence of peripheral vascular disease is a major contraindication, calcified mitral valve annulus or a planned complex repair of the anterior mitral leaflet are relative ones. Preoperative peripheral vascular screening using Doppler-sonography is essential, in addition to assessment of the descending and ascending aorta, as well as the pathology of the mitral valve disease by TEE. This is a new technique enabling less invasive mitral valve operation, which should be approached carefully by a new center. Trained surgeons should already have a basic knowledge of complex mitral valve operation, as well as a training in Port-Access techniques. Careful initial selection of patients and avoidance of high-risk candidates are crucial to obtain results that are equal to conventional mitral valve operation. Any less invasive approach, resulting in improved cosmesis, should not put the patient undergoing mitral valve operation at an additional risk.
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