ANATOMY OF THE PIG-HEART - COMPARISONS WITH NORMAL HUMAN CARDIAC STRUCTURE

Transgenic technology has potentially solved many of the immunological difficulties of using pig organs to support life in the human recipie nt. Nevertheless, other problems still remain. Knowledge of cardiac an atomy of the pig (Sus scrofa) is limited despite the general acceptanc e in the literature that it is similar to that of man. A qualitative a nalysis of porcine and human cardiac anatomy was achieved by gross exa mination and dissection of hearts with macrophotography. The porcine o rgan had a classic 'Valentine heart' shape, reflecting its location wi thin the thorax and to the orientation of the pig's body (unguligrade stance). The human heart, in contrast, was trapezoidal in silhouette, reflecting man's orthograde posture. The morphologically right atrium of the pig was characterised by the tubular shape of its appendage (a feature observed on the left in the human heart). The porcine superior and inferior caval veins opened into the atrium at right angles to on e another, whereas in man the orifices were directly in line. A promin ent left azygous vein (comparable to the much reduced left superior ca val or oblique vein in man) entered on the left side of the pig heart and drained via the coronary sinus. The porcine left atrium received o nly 2 pulmonary veins, whereas 4 orifices were generally observed in m an. The sweep between the inlet and outlet components of the porcine r ight ventricle was less marked than in man, and a prominent muscular m oderator band was situated in a much higher position within the porcin e right ventricle compared with that of man. The apical components of both porcine ventricles possessed very coarse trabeculations, much bro ader than those observed in the human ventricles. In general, aortic-m itral fibrous continuity was reduced in the outlet component of the po rcine left ventricle, with approximately two-thirds of the aortic valv e being supported by left ventricular musculature. Several potentially significant differences exist between porcine and human hearts. It is important that these differences are considered as the arguments cont inue concerning the use of transgenic pig hearts for xenotransplantati on.