New insights in minimally invasive valve replacement: description of a cooperative approach for the off-pump replacement of mitral valves

Aims The aim of the present study was to evaluate whether off-pump mini-invasive mitral valve replacement is possible after prior bioprosthetic mitral valve replacement in animals. Methods and results To validate this concept for off-pump redo mitral valve insertion, we first replaced surgically mitral valves of six sheep under extracorporeal circulation using a Mosaic((R)) valve. Prior to its insertion, we added a radio-opaque ring on its base to enhance its visualization under fluoroscopy. A bovine jugular valve mounted into a stent was then inserted off-pump through an opening of the atrial wall. Mitral valves were replaced successfully in all animals. Following the surgical valve insertion, mean left atrium and left ventricular end-diastolic pressures were 38 (22-42) and 18.8 mmHg (13-22), respectively. Angiography showed perfectly functioning valves, no subaortic valve obstruction, and a mild paravalvular leak in one animal. In one animal, we were unable to control the bleeding from the atrial opening. In this case, trans-atrial valvulation was not attempted. The off-pump valvular implantation was successful in the other five sheep. Haemodynamic data did not change after the insertion of valved stents. Implanted valves were all competent. The animal with the better haemodynamics was kept alive and is still alive 3 months after implantation. Conclusion Surgically implanted bioprosthetic valves provide excellent support for off-pump insertion of a valved stent. Further experiments are necessary, in particular with appropriate valve size, before considering this approach for percutaneous mitral valvular replacement in patients with a dysfunctional bioprosthesis.