ANALYSIS OF CARDIAC SHUNTING IN THE TURTLE TRACHEMYS (PSEUDEMYS) SCRIPTA - APPLICATION OF THE 3 OUTFLOW VESSEL MODEL

Blood distribution within the ventricle was analysed in acutely prepar ed turtles Trachemys scripta by measuring the oxygen concentration and flow rates of blood in the central vessels. Pulmonary (Q(p)) and syst emic (Q(s)) blood flow rates were similar when total cardiac output (Q (tot)) was below 40 ml min(-1) kg(-1). Above this value, increments of Q(tot) were directed to the pulmonary circuit, with Q(s) levelling of f at approximately 20 ml min(-1) kg(-1). When Q(tot) was larger than 4 0 ml min(-1) kg(-1), the systemic circuit was almost exclusively perfu sed by left atrial blood and systemic venous return was almost all dir ected towards the lungs, Blood oxygen levels and flow rates were consi stently higher in the right aorta than in the left aorta. Blood moveme nt within the ventricle, coupled with differences in ejection timing, is probably the decisive factor determining this pattern of blood dist ribution in the turtle heart.