Original ArticleCan We Repair the Mitral Valve from Outside the Heart? A Novel Extra-Cardiac Approach to Functional Mitral Regurgitation
Introduction
Functional mitral regurgitation (FMR) is a common condition that is due to abnormal ventricular mechanics in the presence of normal mitral valve morphology. Mitral valve repair and replacement surgery are accepted as reasonable therapeutic options for the management of severe mitral regurgitation (MR) in patients with heart failure, but with uncertain application and indications [1], [2], [3]. There is a reluctance to refer patients for valve repair or replacement with less-than-severe mitral insufficiency primarily due to the risk associated mitral valve procedures. Mitral valve repair or replacement in the setting of ischaemic heart disease carries a mortality risk of 2–6% [4]. Mitral valve procedures for FMR tend to address the mitral annulus in mitral ring annuloplasty or the leaflets and annulus in mitral valve replacement. However, the problem is predominantly in the ventricle, not in the annulus or the leaflets.
We developed a new extra-cardiac approach, called Basal Annuloplasty of the Cardia Externally (BACE), to address this problem. Applied epicardially to the base of the heart to address the annulus and the sub-annular myocardium, the BACE Device may confer the ability to correct MR by modifying the ventricular component of FMR, with an added benefit of correcting tricuspid regurgitation. Initially, the BACE concept was studied in sheep and validated in patients, which we published in this journal previously [5]. However, those patients were not likely to undergo further surgical procedures. A new device was developed that could be used in younger patients and could be removed at a later stage if further surgical intervention was indicated. This paper narrates evolution of the concept and describes the first evaluation of safety and efficacy of the latest version of the BACE Device in animals and in humans.
Section snippets
BACE Device
The BACE Device consists of a wide, clear dimethylsilicone band assembly with inflatable silicone chambers, including a Bridge chamber that is positioned over the pulmonary trunk, and small belt loops of polyester around the band (Fig. 1). The band is slipped around the base of the heart and positioned at the level of the atrio-ventricular (AV) groove and the adjacent ventricular muscle. The device is held in place with sutures attached to the exterior surface of the heart through tabs on the
Ovine study
All sheep developed severe MR on a combination of echocardiographic parameters after 6–14 weeks of pacing, with a mean mitral annular diameter of 5.03 ± 0.47 cm. Once severe MR was established on echocardiography, the animals were scheduled for BACE Device implantation. Two animals died during induction of anaesthesia, one whilst recovering from endotracheal intubation and general anaesthesia, and one of a perforated ulcer and peritonitis on post-operative day 3 (sheep also may be susceptible to
Discussion
Each version of the BACE concept was evaluated first for safety and efficacy in a sheep model with rapid ventricular pacing. The original BACE proof-of-concept prototype (a band of surgical mesh that partially encircled the heart) was tested in 12 subjects with moderate to severe MR undergoing CABG, LV reconstruction, or both. The results were encouraging with a significant reduction in MR (mean grade of 2.8–0.3), improvement in NYHA functional status (mean 3.1–1.1), and increase in LV ejection
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Transcatheter Therapies for the Treatment of Valvular and Paravalvular Regurgitation in Acquired and Congenital Valvular Heart Disease
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