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Ann Thorac Surg 1999;68:1520-1524
© 1999 The Society of Thoracic Surgeons

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Supplement: Minimally Invasive Cardiac Surgery

Minimally invasive mitral valve surgery through right anterolateral minithoracotomy

^a Escorts Heart Institute and Research Centre, New Delhi, India

Address reprint request to Dr Mishra, Escorts Heart Institute and Research Centre, Okhla Rd, New Delhi-110 025, India
e-mail: ehirc{at}vsnl.com

Presented at Evolving Techniques and Technologies in Minimally Invasive Cardiac Surgery, San Antonio, TX, Jan 22–23, 1999.

Abstract

Background. This study evaluates the feasibility of minimally invasive mitral valve surgery. The aim of the study was to minimize surgical access to achieve better cosmetic results, less postoperative discomfort, and faster recovery.

Methods. From September 1997 to October 1998, 76 patients underwent mitral valve surgery through a right anterolateral minithoracotomy at the fourth intercostal space. The mitral valve was either repaired (n = 21) or replaced (n = 55). In all cases, open femoral artery-femoral vein cannulation was used for cardiopulmonary bypass. In 27 cases, an endoluminal aortic clamp was used, but in 49 cases, the aorta was cross-clamped with a transthoracic, sliding-rod-design clamp.

Results. There were no approach-related limitations to surgical intervention. Intraoperative transesophageal echocardiography revealed excellent results after valve repair and no paravalvular leak in any patient after mitral valve replacement. Mean duration of intensive care and postoperative hospital stay was 32 ± 5.2 hours and 7 ± 1.1 days, respectively. There were no major complications related to femoral vessel cannulation. In 1 patient, transient neurological problems developed, with subsequent complete recovery. There was one hospital mortality (85-year-old male patient died of upper GI bleeding).

Conclusions. Minimally invasive port access mitral valve surgery can accelerate recovery and decrease pain, while maintaining overall surgical efficacy. It also provides better cosmetic results to our patients, and now it has become our standard approach for isolated mitral valve surgery.

Less invasive cardiac surgery has emerged as a new and substantially different approach to a variety of cardiovascular surgical procedures. However, the largest experience in this field is related to coronary artery bypass grafting. Minimally invasive valve surgery may prove even more promising than new coronary procedures, because detailed vascular anastomoses are not required. Recently, limited sternal incisions have been shown to provide excellent exposure for direct-vision, minimally invasive mitral and aortic valve surgery. Using ministernotomy and parasternal incision, Cosgrove, Gundry, and Arom and their associates, among others, have shown encouraging operative results with a low surgical mortality [1–5]. In early 1996, the Stanford Group performed the first four minimally invasive mitral valve replacements using intraaortic balloon occlusion (port access) with cardioplegia [6]. Later, Falk and colleagues, at the University of Leipzig, reported 24 mitral-valve patients operated on successfully using a similar technique [7]. By January 1997, Colvin and Galloway at New York University had done 27 mitral repairs or replacements using this direct-vision method, with a single mortality.

At the meeting of the American Association for Thoracic Surgery in 1997, Mohr presented 51 minimally invasive mitral operations, done using the port-access technique [8]. His detailed description of morbidity and mortality stimulated major concerns regarding retrograde aortic dissection and balloon displacement. At a subsequent meeting, Aklog and associates presented their technique of direct access minimally invasive mitral valve surgery with excellent results [9].

The aim of this work is to evaluate the feasibility of minimally invasive mitral valve surgery, and hence to minimize surgical access to achieve better cosmetic results and less postoperative discomfort to patients, while maintaining at least the same level of safety and favorable results as with conventional surgery.

Material and methods

Between September 1997 and October 1998, 76 patients underwent mitral valve surgery by means of a minimally invasive approach through a right anterolateral minithoracotomy at the fourth intercostal space under direct vision. There were 26 males and 50 females with a mean age of 35.2 ± 10.7 years. As is shown in Table 1, most of the patients were having rheumatic valvular pathology, whereas 11 had degenerative mitral pathology. Along with mitral valve disease there were 28 patients who had involvement of tricuspid valve; out of those, 6 required tricuspid valve repair along with mitral valve surgery.

Surgery
Patients were positioned in a supine position with the right side of the chest slightly elevated. Usual anesthetic techniques were used. In 23 cases, a transjugular coronary sinus catheter (Heartport, Inc, Redwood City, CA) was inserted under transesophageal echocardiography (TEE) and C-arm guidance for retrograde cardioplegia[10]. Transjugular endovascular pulmonary vent (Heartport, Inc, Redwood City, CA) was used in 21 cases. Flow-directed pulmonary artery catheter was inserted in only those patients who had very high pulmonary artery pressure on preoperative evaluation. The right or left femoral artery and vein were surgically exposed through a 3- to 4-cm incision parallel to the inguinal skin fold. After systemic heparinization, a 21 F, Y-shaped arterial return cannula (Heartport, Inc, Redwood City, CA) or 21 F straight cannula (DLP, Inc, Grand Rapids, MI) was placed in the femoral artery depending on whether an endoaortic or transthoracic occlusion clamp was being used. A 28 F venous return cannula (Heartport, Inc, Redwood City, CA) was placed in the femoral vein and advanced to the right atrium and then to the superior vena cava under TEE control. A conventional cardiopulmonary bypass system with roller pump and membrane oxygenator was used. In addition, a centrifugal pump (Sarns Inc, Ann Arbor, MI) was placed in the venous line to enhance venous drainage.

Simultaneously, a 5- to 8-cm-long incision was made anterolaterally over the fourth intercostal space. After initiation of cardiopulmonary bypass, the lungs were deflated. The pericardium was opened 3 cm above, and parallel to, the right phrenic nerve to expose the roof of the left atrium. Exposure was enhanced by placing stay sutures on the pericardium, which were fixed to the chest wall. Cardiopulmonary bypass was instituted with temperature drift, without active cooling or warming until the aortic cross-clamp was in place. Before insertion of the endovascular aortic clamp, with the aid of TEE, the aorta was screened for atheromatous debris and thrombi to avoid cerebral embolization with retrograde perfusion. Advancement of the guidewire could be visualized from the descending aorta to the aortic valve by TEE. Correct placement of the clamp (1 cm above the level of the sinotubular junction) was controlled by fluoroscopy (Sieremobil 2000, Siemens, Erlangen Germany) and multiplane TEE (Sonas 5500 Hewlett Packard, Inc, Andover, MA). The endovascular aortic clamp was inflated to endoluminally block the ascending aorta while the heart was vented through the endovascular pulmonary vent and the distal lumen of the endovascular aortic clamp in the aortic root. After clamping, balloon pressure was continuously measured and maintained between 250 and 340 mm Hg. Additional volume was inflated in case of a decrease in balloon pressure below 250 mm Hg. Warm-blood cardioplegic solution was delivered antegradely through the distal endovascular clamp lumen while maintaining aortic root pressure between 50 and 70 mm Hg. In initial 23 cases, retrograde cardioplegia was also used as a adjunct to antegrade cardioplegia through a coronary sinus catheter placed transjugularly. The endoaortic clamp was used in initial 27 cases, but now our preference is the transthoracic, sliding-rod aortic clamp (Scanlan International, Inc., Minneapolis, MN) which was used in 49 cases in the present series (Figure 1). This clamp is passed through third intercostal space at the midclavicular line through a 3-mm port. For antegrade cardioplegia delivery, the DLP cardioplegia catheter (DLP, Inc, Grand Rapids, MI) was used; the DLP catheter was also used for aortic root suction during air removal. After cardiac arrest was established, the left atrium was opened and the mitral valve exposed by a specially designed atrial retractor (Heartport, Inc, Redwood City, CA) inserted through another 3-mm port at the fifth or sixth intercostal space parasternally. Mitral valve repair or replacement was performed under direct vision with the use of a specially designed instrument (Heartport, Inc, Redwood City, CA). After completion of the procedure, the left atrial vent was positioned across the mitral valve and the left atrial incision was closed.

View larger version (46K): [in this window] [in a new window]   Fig 1. Transthoracic sliding-rod design aortic cross clamp. The clamp mechanism works completely within the thorax.

Air removal was performed by inflation of the lungs and simultaneous reduction of venous drainage with the patient placed in the Trendelenburg position. Aortal air removal was performed by suction through the distal lumen of the endovascular aortic clamp or cardioplegia catheter (depending on which was in place). The endovascular aortic clamp was deflated and the catheter was left in place for further venting until air removal was complete. If necessary, defibrillation was performed using external defibrillation pads. A temporary pacing wire was placed in the right ventricular epicardium before the aortic cross-clamp was released. Once air removal was complete, the endovascular aortic clamp or cardioplegia catheter at aortic root was removed. After appropriate reperfusion, the arterial and venous cannulae were removed and the femoral vessels were reconstructed. The chest wound was closed after inserting a drainage tube into the pleural space.

Follow-up
Postoperative follow-up included 3-month, then 6-month postoperative visits, followed by annual follow-up with serial echocardiography when possible. Preoperative, operative, and postoperative data were prospectively collected and stored in a prescribed form and database.

Results

Catheter placement
Positioning of the endovascular pulmonary vent was was inserted in 21 cases and was successful in all. Positioning of the transjugular coronary sinus catheter was tried in 26 cases, but was not successful in 3 cases. Cannulation in the groin was performed without complications in all patients. Placement and positioning of the endovascular clamp was uneventful whenever it was tried. In all patients, injection of an initial volume of 20 to 35 ml saline resulted in sufficient aortic occlusion with a balloon pressure in the desired range of 240 to 360 mm Hg. In 4 patients, additional volumes had to be added because the balloon pressure decreased below 250 mm Hg during the procedure. Migration of the balloon during initial placement was observed in 4 patients but was easily corrected by external manipulation of the catheter under TEE control.

Transthoracic sliding-rod aortic cross-clamping
No aortic clamp-related injuries occurred. Clamp occlusion was not difficult and antegrade cardioplegia provided excellent cardiac protection.

Surgical technique
In all patients, the mitral valve was accessible through the right anterolateral minithoracotomy. The mean length of incision was 6.8 cm ± 1.8 cm (range 5 cm to 8.6 cm).

In 21 patients, the mitral valve was repaired by a combination of techniques including commissurotomy, sliding plasty, and annuloplasty with a Carpentier Edwards ring (Baxter Healthcare Corp, Irvine, CA). As demonstrated by intraoperative TEE, successful repair was achieved in all patients. In 1 patient post mitral valve replacement (MVR) parvalvular leak was closed with a Dacron patch (Table 2). In 1 patient left atrial clot was removed and mitral commissurotomy was done. In 3 patients tricuspid valve repair was performed along with mitral valve repair. In the repair group, 1 patient had atrial septal defect, which was closed by a pericardial patch. Fifty-five patients underwent mitral valve replacement, with preservation of posterior mitral leaflet in 41. In the remaining 14 cases posterior leaflet was heavily calcified and could not be preserved. In 3 patients, tricuspid valve replacement was performed for severe artery regurgitation, along with mitral valve replacement. In 1 case in the replacement group, atrial septal defect was also present, which was closed with a pericardial patch. In 1 patient, in the replacement group, an atrial septal defect We prefer to use the Starr Edward Mitral valve prostheses (Baxter Healthcare Corporation, Edwards CVS Division, Irvine, CA) for the ease of anticoagulation management in our patient. In 1 patient, the Carpentier Edward bioprosthesis (Baxter HealthCare Corp, Irvine CA) was used. Mean duration of cardiopulmonary bypass and cross-clamp times were 96 ± 52 minutes and 54 ± 27 minutes, respectively. In 68 patients, a spontaneous sinus rhythm was observed after the release of the aortic clamp, where as 8 patients required one or more external defibrillations of 200 to 300 joules for ventricular fibrillation.

Comment

The right anterolateral minithoracotomy for minimally invasive mitral valve surgery seems very suitable, because this incision provides a direct line view of the left atriotomy with minimal patient discomfort. Two-thirds of our patients who came for mitral valve surgery were young women; hence this incision gives better cosmetic results than any other incision because it remains hidden underneath the breast. Our strategy of switching to the transthoracic aortic clamp in place of the endoaortic clamp seems logical, because the transthoracic aortic clamp method appears safe and requires few additional resources or disposable supplies. Transthoracic-clamp occlusion was not difficult and antegrade cardioplegia provided excellent cardiac protection. The Endoclamp developed by Heartport Inc. provides similar intraluminal aortic occlusion and antegrade cardioplegia capabilities, but the procedure becomes costly when we use the Endoclamp instead of the transthoracic aortic clamp. In our experience, there was no incidence of aortic dissection with the use of the Endoclamp as was reported by Mohr and associates [8], but this may be because our patient population was much younger. We also did not have complications related to femoral artery cannulation as reported by Mohr and associates [8] and Aklog and associates [9], probably because of the younger age of our patients. In 4 patients, we observed inadvertent balloon migration, which was easily detected by differences in mean pressure of right and left radial arteries due to innominate occlusion and reconfirmed on TEE. In all the four cases, balloon position was easily adjusted without causing any damage.

With increasing experience, cardiopulmonary bypass and cross-clamp times became shorter in this series. The length of the thoracotomy incision has steadily decreased, and none of the patients required rib resection. As compared to other reported series, [8,11] the thoracotomy incisions in our series were bigger because we carried out the procedure under direct vision and not with a thoracoscope. Most of our patients were young females; accessing the fourth intercostal space in these patients requires a larger incision than that required in male patients.

The decision to repair a mitral valve should not be influenced by the operative approach, but rather by the abnormality of the valve. The quality of the final result should never be compromised to minimize hospital costs, improve cosmesis, or lessen temporary discomfort. In the present series we were able to carry out repair procedures in only 21 cases, which is 27.6% of the total number. This is because we mainly deal with rheumatic pathology, which leads to significantly deformed and calcified mitral valves, which are not suitable for repair.

Seven patients were redo cases. One patient had aortic valve replacement and 1 had coronary artery bypass grafting. In 1 patient, the mitral valve was replaced 1 year earlier by us, but he developed a paravalvular leak. Another 4 patients had closed mitral commissurotomy before they came for open-mitral-valve surgery. Postaortic valve replacement, coronary artery bypass grafting, and mitral valve replacement patients were cases well-suited for using the endoaortic clamp to avoid extensive dissection to a clear aorta. In 4 patients, who had prior closed-mitral-valve commissurotomy, adhesions were not as dense and we were able to dissect the aorta easily to apply the transthoracic aortic clamp. In our experience, right minithoracotomy is an excellent approach to reaching the mitral valve in patients who had previous cardiac surgery through midline sternotomy.

Patients having minimally invasive procedures experienced much less chest-tube drainage, and overall they required fewer transfusions and re-explorations for bleeding. In the present series, the median blood loss was only 400 ml and only 1 patient required re-exploration for bleeding.

The operative mortality of 1.3% and the excellent early echocardiographic results certainly attest to the safety and efficacy of this approach, similar to those of conventional mitral valve surgery. However, the minimally invasive technique clearly required more time in the operating room. The extra ischemic time is the result of some additional technical maneuvers performed to enhance exposure. The extra cardiopulmonary bypass time is mostly due to extra precautions necessary to properly remove air from the heart by TEE control.

In conclusion, our results of minimally invasive mitral valve surgery suggest that the procedures are safe and may benefit patients through reduced intensive care unit stays, lower transfusion requirements, less operative discomfort, better cosmetic results, and earlier hospital discharge. Both mitral valve repair and replacement can be done with this approach with good operative results. The use of transthoracic aortic clamp in place of endoaortic clamp has the benefit of not requiring additional resources. This is an excellent approach for mitral valve surgery in patients who had previous cardiac procedures. The benefits of minimally invasive mitral valve surgery can be countered because of current increased operative times and greater technical challenges. Further experience with this procedure and technical advancements like the use of video thoracoscope may help us to overcome these concerns.

Acknowledgments

Special thanks to Ms Pooja Arora for excellent secretarial assistance.

References

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