Long‐term outcome in a case of translocated mitral valve replacement for massive mitral annular calcification

Key Clinical Message Few reports have described long‐term outcomes after translocated mitral valve replacement. We describe tips, potential pitfalls, and long‐term outcome associated with the construction of a new mitral annulus and reinforcement of prosthesis attachment using a mitral prosthetic valve with an equine pericardial collar in a woman with extensive mitral valve calcification.


Background
Calcification of the mitral valve (MV) annulus is an age-related degenerative process that involves the posterior aspect of the annulus, and it can spread to the atrial and ventricular walls [1]. Severe calcification of the MV annulus is often observed in patients undergoing long-term hemodialysis. In most cases of MV repair among patients with extensive calcification of the mitral annulus, calcification prevents appropriate insertion of the prosthetic valve, and it may increase the frequency of postoperative periprosthetic leakage or valvular dehiscence [2]. Moreover, MV replacement (MVR) in this setting may be associated with a high risk of fatal complications such as left ventricular rupture, coronary circumflex artery injury, and thromboembolic events [1]. Furthermore, long-term durability after translocated MVR is unknown. We performed modified translocated MVR in a patient with extensive annular calcification of the MV to reduce the occurrence of fatal operative complications and postoperative periprosthetic leakage or valvular dehiscence for improved long-term outcomes.

Case Report
A 55-year-old woman on hemodialysis for chronic glomerular nephritis for 18 years had undergone dualchamber pacemaker implantation because of a complete atrioventricular block 4 years before presentation. The preoperative transthoracic echocardiogram indicated severe mitral stenosis with an estimated pressure gradient of 15 mmHg and a MV area of 0.8 cm 2 . In particular, the posterior leaflet of the mitral annulus, a part of the left ventricle, and papillary muscles were severely calcified (Fig. 1). The preoperative computed tomography scan demonstrated severe calcification around the mitral annulus and calcification invading the left ventricle. Cardiac catheterization showed normal coronary arteries with normal left ventricular function (ejection fraction, 70%).
The operation was performed through median sternotomy. Cardiopulmonary bypass was established through ascending aortic cannulation and bicaval drainage. A left venting tube was inserted through the right superior pulmonary vein. After cardiac arrest, the right side of the left atrium was incised. The tissue surrounding the mitral annulus, especially the posterior mitral annulus, posterior leaflet, and part of the anterior leaflet, including the chordae, were severely calcified. The posterior leaflet and part of the anterior leaflet could not be excised because of extensive calcification. For MVR, four sutures were placed at the supraannular position on the anterior mitral annulus. Eleven additional sutures were placed through all the layers of the left atrial walls so that they wrapped around the posterior mitral annulus ( Fig. 2A   prosthetic valve during the systolic and diastolic phases ( Fig. 3A and B). The patient's postoperative course was uneventful, and she was discharged on the fourteenth postoperative day. She had satisfactory improvement, and the transthoracic echocardiogram showed normal prosthetic valve function without periprosthetic leakage and a mean transvalvular pressure gradient of 6 mmHg at 45 months postoperatively.

Discussion
In patients undergoing dialysis, mechanical stress caused by hypertension and a high cardiac output due to an arteriovenous shunt can lead to the development of mitral annular calcification, which in some cases may extend to the valve leaflets and myocardium [3]. Several surgical techniques have been used to manage extensive calcification at the mitral annulus, such as the active removal of calcification and posterior mitral annular reconstruction using an anterior MV patch [4,5] to create a new annulus [6,7], or a combination of these techniques [2]. Complete calcium debridement may cause atrioventricular rupture, left circumflex coronary artery damage, and/or thromboembolic events [1]. Intra-atrial insertion of the prosthesis after constructing a new annulus may lead to severe hemorrhage or valve dehiscence due to the transfer of high left ventricular pressure into the left atrium [8].
To prevent fatal complications in the present patient, we did not remove the posterior mitral leaflet and part of the anterior mitral leaflet because of extensive calcification. The technique of avoiding active removal of severe calcification was considered reliable and reproducible. We propose the following three approaches during modified translocated MVR to reduce complications. First, all needles should exit in the same arterial plane, as this enables the prosthesis to be placed in the supraannular position, thus reducing periprosthetic leakage. MVR performed in the supraannular position enables surgeons to insert a larger prosthesis. Second, the sutures should be placed through all the layers of each of the two atrial walls so that they wrap around the posterior mitral annulus. In addition, the mitral prosthetic valve with an equine pericardial collar should be sutured using a running 4-0 polypropylene suture to reinforce the attachment of the prosthetic valve. Finally, the SJM expanded cuff of the mitral prosthetic valve should be used, as it increases the contact area between the sutured cuff and atrium and prevents disturbance of the opening of the prosthetic leaflets caused by the remaining extensively calcified native posterior leaflet. SJM valves have the advantage of causing minimal interference between the leaflets and subvalvular tissue because the height of this valve leaflet from the support frame is the lowest (3.4 mm) among other mitral mechanical prostheses [9]. Kato et al. reported that a paravalvular leak occurred in one of five patients who had undergone MVR by simple supraannular prosthesis insertion [10]. From their viewpoint, sutures of the sewing cuff, both layers of the left atrial wall, and collar patch are very important to reduce the chance of a paravalvular leak. However, surgeons need to pay attention to avoid involving the left circumflex artery when placing sutures on the posterior side of the left atrial wall.
We consider that using these techniques, translocated MVR can reduce the perioperative risk and limit reintervention after MVR in a patient with extensive calcification of the mitral annulus, especially when the calcified posterior mitral leaflet cannot be excised. We believe that our techniques may be suitable for performing MVR in patients with extensive calcification of the mitral annulus, and good long-term outcomes may be obtained.

Consent
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the editor in chief of this journal.