Original Article
Can We Repair the Mitral Valve from Outside the Heart? A Novel Extra-Cardiac Approach to Functional Mitral Regurgitation

https://doi.org/10.1016/j.hlc.2010.12.001Get rights and content

Background

Functional mitral regurgitation (FMR) is primarily due to abnormalities of the ventricular muscle in the presence of normal mitral leaflets. Present surgical treatment options address the mitral valve annulus and leaflets but not the ventricular muscle. We discuss the evolution of a concept that describes a ventricular solution to this problem, and report preliminary clinical results from the first five subjects implanted with the latest version of this device.

Methods

Evaluation of safety and efficacy of the latest version of the BACE™ (Basal Annuloplasty of the Cardia Externally) Device was done first in sheep with rapid ventricular pacing to induce severe MR. The BACE Device was implanted around the base of the heart and chambers on the device filled with normal saline through the subcutaneous ports under echocardiogram until there was no evidence of MR. Once MR was effectively reduced, the chest was closed and the animals recovered, with clinical and echocardiographic analysis through six months of follow-up. Human studies were done with in a similar manner, with subjects that were already undergoing concomitant open-chest coronary artery bypass graft (CABG) surgery. Five subjects with ischaemic MR and triple vessel coronary artery disease were first implanted with the BACE Device, applied epicardially on a beating heart without use of cardiopulmonary bypass, before coronary artery bypass grafting was done.

Results

In five sheep, epicardial application of the BACE Device effectively reduced mitral regurgitation from Grade 4 to Grade 0, and the effect was sustained through six months despite ongoing pacing. Terminal studies at six months showed no adhesion to the silicone band. All five human subjects were male, NYHA Class III, with LVEF of 20–40%. Epicardial application and adjustment of the BACE Device was performed safely on a beating heart with effective reduction in FMR to grade <1. All five subjects had three bypass grafts. Reduction in MR was sustained for at least six months and there were no unanticipated or device-related adverse events.

Conclusion

Epicardial application and adjustment of the BACE Device can be performed safely without CPB with effective reduction in MR.

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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