Cardiac valve repair: novel techniques

Aims Heart valve repair today includes several preclinical and clinical trans-catheter techniques, including the Evalve MitraClip, for mitral valve (MV) regurgitation by approximating the leaflets, creating a double orifice valve. This is undergoing clinical evaluation in the United States and is commercially available in Europe. We report the pathological findings of explanted MitraClip devices following chronic implantation in the porcine model. Methods Twenty-one explanted porcine valves with MitraClip devices (implanted for 4, 12, 17, 24 and 52 weeks) were examined with light (16) and electron microscopy (5). All were examined, and submitted for routine histology and methyl methacrylate embedding. Haematoxylin and eosin, Gram and connective tissue stains were used. Results Tissue in-growth and endothelialisation, proportional to duration of implantation, were found on the flow (atrial) and non-flow (ventricular) surfaces of the device. This tissue ‘encapsulated’ the device and bridged the gap between the mitral leaflets. Adjacent chordae tendinae were progressively incorporated into the fibrous tissue on the device, as early as 4 weeks, and in 100% of clips by 52 weeks. Conclusions (1) The MitraClip device provides functional tissue apposition;(2) host tissue encases the device, but the valve continues to function well;(3) no device thrombosis was seen.