OPTIMAL SHAPE OF PROSTHESIS FOR TRICUSPID-VALVE REPLACEMENT

To develop an optimal prosthesis for use in the tricuspid valve, we de termined the change in cardiac performance associated with the change in shape of the anulus of the tricuspid valve using a metal ring of va riable flat ratio (defined as the long/short axis). In experiment I in an isolated autoperfusion model with six dogs, the left ventricular s troke work under a constant left atrial pressure of 7 mm Hg were, in g rams per beat per minute, 11.88 +/- 0.52 with a flat ratio of 1.0, 11. 88 +/- 0.70 with a flat ratio of 1.3, 16.23 +/- 0.61 with a flat ratio of 1.6, and 11.22 +/- 0.38 with a flat ratio of 2.3 (mean +/- standar d error of the mean). The volume was significantly higher with a flat ratio of 1.6 than with the other ratios (p < 0.05). In experiment II w ith six dogs in vivo, the blood flow of the pulmonary trunk artery was 0.57 +/- 0.03 L/min with a flat ratio of 1.0, 0.66 +/- 0.03 L/min wit h a flat ratio of 1.6, and 0.58 +/- 0.03 L/min with a flat ratio of 2. 3; the flow was significantly larger with a ratio of 1.6 than with the other ratios (p < 0.05). Right ventriculography was performed in five dogs. The percentage of radial shortening of the apex close to the ac ute margin was 19.4 % +/- 3.1 % with a flat ratio of 1.0 and 49.2 % +/ - 5.1 % with a flat ratio of 1.6 (p < 0.05). In conclusion, the best h emodynamic results were obtained with a flat ratio of 1.6, which showe d more advantageous hemodynamics than do the ratios of conventional ci rcular prostheses.