SUCCESSFUL PROSTHETIC MITRAL-VALVE IMPLANTATION IN PIGS

Clotting mechanisms, the coagulation cascade, platelet function, and p latelet-leukocyte-endothelial cell interactions are all very similar i n humans and pigs. Because of these similarities, the authors conclude d that the pig would be an ideal model for the study of thromboembolis m resulting from prosthetic heart valves. To date, they have successfu lly recovered a total of 11 pigs (52.9 +/- 8.1 kg), 3 with bioprosthet ic valves and 8 with mechanical valves, all in the mitral position (25 mm ed). The normal presence of high numbers of pulmonary endothelial macrophages and other unique aspects of porcine cardiovascular and pul monary function dictate somewhat different surgical protocols than tho se normally used for human patients and ruminant species. Some of thes e special procedures include 1) crystalloid prime without the use of p lasma volume expanders, especially those with a starch base; 2) pharma cologic protection against arrhythmias (lidocaine, 4 mg/kg); 3) specia l attention to adequate hypothermic cardioprotection during the time o f cross-clamp; 4) the use of shock doses of corticosteroid (prednisolo ne sodium succinate, 0.5 mg/kg) before removal of the aortic cross-cla mp; and 5) positive inotropic support (dopamine, 0.008 mg/kg) while we aning from cardiopulmonary bypass. Gamma camera images of (111)ln tagg ed autologous platelets 24 hours after surgery show most thrombi locat ed on the sewing ring with fewer on the pledgets and anchor sutures. T he latter observations were confirmed by quantification of platelet de position using a gamma counter.