Ann Thorac Surg 1999;68:255-257
© 1999 The Society of Thoracic Surgeons
Case Reports
Left ventricular outflow tract obstruction with mitral mechanical prosthesis
José M. Melero, MDa,b,
Isabel Rodriguez, MDa,b,
Miguel Such, MDa,b,
Carlos Porras, MDa,b,
Eduardo Olalla, MDa,b
a Department of Cardiac Surgery, Virgen de la Victoria University Hospital, Málaga, Spain
b Department of Cardiology, Virgen de la Victoria University Hospital, Málaga, Spain
Address reprint requests to Dr Melero, Department of Cardiac Surgery, Virgen de la Victoria University Hospital, Campus Universitario Teatinos, 29010 Málaga, Spain
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Abstract
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Left ventricular outflow tract obstruction after mitral valve replacement may occur when the native mitral apparatus is preserved intact. Although it has usually been reported using bioprostheses, we present one case using a low-profile mechanical prosthesis. The reduction of left ventricular dimensions and valvular redundancy contributed to this complication. We obtained definitive relief of left ventricular outflow tract obstruction by transaortic exposure and partial resection of the obstructing tissue with the help of video-assisted cardioscopy.
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Introduction
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Complete preservation of the native mitral apparatus when mitral valve replacement (MVR) is performed harbors the potential for left ventricular outflow tract obstruction (LVOTO), which most frequently results from implantation of a high-profile bioprosthesis, as described in previous reports [1–3]. We present one case of LVOTO after MVR with entire retention of the native mitral apparatus using a low-profile mechanical prothesis. We analyze the potential mechanism of action and describe the simplified correction of LVOTO throughout aortotomy with the help of video-assisted cardioscopy.
A 61-year-old woman with a history of recurrent episodes of cardiac failure was admitted for increasing dyspnea. Echocardiography showed severe mitral regurgitation with a prolapse of the anterior leaflet. There was no evidence of narrow outflow tract. The systolic function was normal. Catheterization revealed normal coronary arteries. At operation, the native mitral valve was found to have myxomatous leaflets and chordae. Annular calcification, highly redundant mitral leaflets, and greatly elongated chordae contraindicated valvular repair. A Carbomedics 27-mm mechanical prosthesis (Carbomedics Inc, Austin, TX) was implanted without excising any mitral valvular or subvalvular tissue. Sutures were passed from the left atrium, through the mitral annulus, around the mitral leaflet, thus reefing the native leaflets and compressing them between the prosthetic and native annuli, as described by Vander Salm and associates [4]. The procedure was uneventful and the patient was discharged 8 days after surgery.
The patient was readmitted for congestive failure with a prominent systolic murmur 3 months after discharge. Echocardiography was performed. The left ventricular dimensions had decreased when compared with preoperative register. The systolic function was normal. Anterior mitral leaflet and its chordae had anterior systolic displacement toward the interventricular septum, narrowing the left ventricular outflow tract. Continuous-wave Doppler detected a peak systolic gradient of 89 mm Hg. Prosthetic leaflets motion and transvalvular gradient were normal.
The patient was managed medically for 1 month, but persistent dyspnea and unaltered transaortic gradient mandated reoperation. Dissection was limited to that needed for exposure of the right atrium and the ascending aorta. The aorta was opened. Through the retracted aortic valve, with the help of video-assisted cardioscopy, we could see the reefed anterior mitral leaflet and its chordae abutting on the ventricular septum (Fig 1). When the chordae corresponding to the anterior leaflet were resected, the prosthetic annulus and anterior leaflet, which was left intact, separated from the outflow tract (Fig 2). Perioperative transesophageal echocardiography and the measurement of pressure in left ventricle and aorta demonstrated no gradient and the elimination of LVOTO. The patient was discharged 6 days after surgery and she is asymptomatic at 6-month follow-up.
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Fig 1. Intraoperative endoscopic image through the retracted aortic valve shows the reefed anterior mitral leaflet and its chordae that occupy the left ventricular outflow tract.
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Fig 2. Endoscopic view through aortotomy after resection of the chordae corresponding to the anterior mitral leaflet. The chordae of the posterior leaflet can be seen at the bottom.
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Comment
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A possible disadvantage of leaving the leaflets intact after MVR is LVOTO, which most frequently results from implantation of a high-profile biological prosthesis, as described in previous reports [1–3]. Cases of LVOTO after implantation of a low-profile mechanical prosthesis as we present are uncommon.
After analyzing the echocardiographic features, we noted a reduction in left ventricular dimensions postoperatively and systolic anterior motion of the anterior mitral leaflet and its chordae toward the interventricular septum. This phenomenon could be caused by a Venturi effect, with systolic emptying that would pull the anterior leaflet and its chordae toward the outflow tract and would be enhanced by redundancy of the preserved native anterior valve and chordae, by a vigorous contractility and by postoperative reduction of the left ventricular dimensions [2, 3]. Surgical findings demonstrated that the outflow tract was occupied by the anterior leaflet and, above all, the chordae tendineae. The direction and position of the chordae had changed by reefing the anterior leaflet, so that the chordae pulled from the anterior leaflet toward the outflow tract of the left ventricle.
Prevention is the best treatment of LVOTO after MVR with preservation of the mitral valve apparatus. There have been reported multiple techniques to prevent LVOTO. Most of them consist of transferring part of the anterior leaflet with its chordae from the proximity of the left ventricular outflow tract [5, 6]. But, when the anterior mitral leaflet and chordae tendineae are very redundant, to try to prevent LVOTO by reefing the mitral leaflets within the valve sutures, as we did or Vander Salm proposed [4], even using low-profile mechanical prosthesis, is not a safe technique.
Once the diagnosis of severe LVOTO is made, a conservative therapeutic attitude may allow for insidious development of left ventricular failure with an adverse clinical outcome [2]. We recommend early surgical treatment in these cases. When the mechanism is redundant chordae tendineae that pulled the anterior mitral leaflet toward the outflow tract, an easier and resolutive technique can be a transaortic approach, which minimizes dissection and achieves a comfortable exposure [7]. In these cases only, it is necessary to excise the chordae that anchor on the anterior leaflet, while the rest of the mitral apparatus is left intact. Use of video-assisted cardioscopy can facilitate correction of LVOTO.
In summary, insertion of a low-profile mechanical prosthesis does not always avoid LVOTO when anterior and posterior mitral leaflets with their subjacent chordae are preserved. Prevention is the best treatment, but when LVOTO is established, a limited approach throughout an aortotomy simplifies the surgery.
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References
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Come P.C., Riley M.F., Weintraub R.M., et al. Dynamic left ventricular outflow tract obstruction when the anterior leaflet is retained at prosthetic mitral valve replacement. Ann Thorac Surg 1987;43:561-563.[Abstract]
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Accepted for publication December 30, 1998.
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Abstract
Introduction
