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Abstract
The opening angle of the Björk-Shiley mitral prosthesis was increased from 50° to 60° and the prosthesis rotated 180° in the mitral annulus to direct the downward moving part of the disc towards the posterior leaflet base, in an attempt to optimize the pressure-flow relationship of the prosthesis. The material for the disc occluder was changed to pyrolytic carbon and the new sewing ring had two flanges. Thirty-one consecutive patients with isolated mitral lesions were studied before and 5-12 months following mitral valve replacement. Prior to operation, 25/31 (81 %) of the patients were in N.Y.H.A. function class III or IV, 28/31 (90 %) were in atrial fibrillation, the central circulation was markedly hypo-kinetic and the left + and pulmonary artery pressures were markedly elevated.
Early mortality within 1 month of operation was 6 %, while there was no late mortality after an observation period of 12-24 months. Subjective and N.Y.H.A. function class improvement was observed in 22/27 (82 %). Thrombo-embolic complications occurred in 2 patients (7 %). All patients were anticoagulated. Persistent atrial fibrillation was found in 13/27 (48 %). The central haemodynamics were markedly improved with increased stroke volume and cardiac output, decrease in left atrial and pulmonary artery pressures and reduction in both pulmonary and systemic vascular resistance. The pressure-flow relationships of the prostheses were studied and found to be highly satisfactory. A persistent large left atrial u-wave was a common finding.
The clinical and haemodynamic results are discussed and the present material is compared with a similar one in which the prosthesis opened at an angle of 50 and was rotated with the large orifice towards the anterior mitral leaflet. The more favourable pressure-flow relationships across the mitral orifice are discussed and it is suggested that the posterior rotation of the prosthesis is themost important factor. In order to achieve this aim, the prosthesis was rotated 180° with the larger downward moving portion of the disc directed towards the posterior mitral leaflet base.
The purpose of the present investigation was to study the effect on the central haemodynamics of these changes.