Implantation of a new mitral ring, adjustable during follow-up: a simplified technique

Abstract

Mitral valve repair for ischaemic mitral incompetence has a 10% rate of failure at ten year follow-up. Progressive annular dilation could play an important role. We have implanted the enCor_SQ^TM mitral valve repair system. This system can be downsized during follow-up with the appropriate activation via the lead passed through the left atrium suture line, in order to restore mitral leaflet coaptation.

INTRODUCTION

Ischaemic mitral incompetence is present in 18% of patients with coronary artery disease [1]. In the majority of cases, mitral valve repair has been proven to be superior to replacement [2]. However, due to progression of the ventricular disease, there is a 10% incidence of failure of repair at ten year follow-up. In this situation, annular dilation can play a major role. A mitral valve repair system, the enCor_SQ^TM annuloplasty device (MiCardia Corporation, Irvine, CA, USA), has recently become available in Europe, in which it is possible to reduce the size of the annulus during follow-up (Fig. 1). The system consists of a semi-rigid mitral ring with a nitinol core, protected by a silicon cylinder and a polyester cover. The activation line is covered with polyester for 7 mm and thereafter with silicon. The activation line is located at P3. We present a simplified approach to implanting the device.

Figure 1:

enCor_SQ^TM mitral valve repair system, MiCardia Corporation, USA.

CONCEPT

The surgical approach to the mitral valve is made, in standard fashion, through left atriotomy after arresting the heart with mild hypothermic blood cardioplegia. The mitral valve complex is inspected and, if a Type I or III B lesion (according to Carpentier classification) is present, the size of the ring is measured using the inter-trigonal distance. In general, the selected ring is one size smaller than the exact measurement. The enCor_SQ^TM mitral valve repair system is implanted in the normal way (2/0 Ticron interrupted suture), taking care to insert the stitches in the ring outside the green line and with the activation line connected to the external generator, in order to avoid and monitor possible damage to the nitinol core. The activation line is fixed to the left atrial wall, taking care to plicate the endocardium to cover the silicon part as far as the atriotomy (usually 2–3 stitches). In this way, any free movement of the lead in the atrium is avoided (Fig. 2). The activation line is then passed through the left atriotomy, which is closed in the normal way and the exit point reinforced with a 4/0 Prolene suture with pledget. The patient is weaned from extracorporeal circulation as usual and the repair is controlled with transoesophageal echocardiography (TEE). Care is taken to fix the lead to the pericardium in order to avoid possible interference with the drainage tubes. The activation lead and electrode are located under the subcutaneous tissue through the inferior part of the sternotomy for future use, as is usually done for epicardial permanent pacemaker wires.

Figure 2:

enCor_SQ^TM system implanted. Arrow: plication of the atrial endocardium over the silicon-covered part of the lead.

DISCUSSION

If necessary, this novel ring allows the device to be reduced in size during follow-up, in order to restore the competence of the mitral valve with the aim of reducing myocardial overload and a possible second operation. A previous version of the ring allowed the ring to be down-sized in the operating room. Frank Langer and co-workers performed a multicentre trial with the previous version of the ring, MiCardia's DYANA annuloplasty system, reporting good performance [3]. The difference, in this new version, is the presence of a permanent lead that allows the ring to be down-sized during follow-up. The enCor_SQ^TM mitral valve repair system was implanted, in our institution, in two patients with severe mitral incompetence, one classified as Carpentier Type I and one as Carpentier Type III B. Both patients were in NYHA class III. The postoperative course was uneventful. At two months follow-up, no mitral incompetence was present and the patients were in NYHA class I. No activation of the ring has been performed.

MiCardia suggests passing the polyester-covered part of the activation lead through the posterior aspect of the left atrium near P3, in order to prevent coagulation problems with the silicon-covered part or movement of the lead inside the atrium. However there are a few drawbacks: 1) bleeding problem difficult to handle coming out of bypass, 2) damage to the coronary sinus, 3) more importantly, distortion and undue tension on the ring in the zone of P3 that is often of particular importance in ischaemic mitral incompetence [4]. Our technique of covering the silicon part of the lead with a plication of the endocardium allows this ring to be implanted in an easy and safe way, avoiding any possible thrombosis and tension.

Conflict of interest: none declared.