A model for quantitative sampling of myocardial venous blood in the pig

A lack of good models for studies of myocardial metabolism prompted us to develop a model which allows the continuous measurement of myocardial blood flow and sampling of adequate amounts of coronary sinus (c.s.) blood without admixture of blood from the right atrium, with the working heart in situ. In the pig the left azygos vein drains into the c.s. and can easily be cannulated after thoracotomy. Thus, a shunt to the right atrium can be established by closing the entrance of the c.s. into the right atrium by a stitch ligature. More than 90% of shunt flow originates from the left ventricular myocardium. It is presently shown that establishing the shunt does not compromise myocardial flow, and there are no observable changes in left ventricular pressure, flow or dimensions. Myocardial flow in the drained and adjacent regions, as determined by injections of microspheres, and flow determined by electromagnetic flowmetry on the shunt are all identical. The model is stable during aortic constriction and isoproterenol infusion which induce expected changes in myocardial flow- and oxygen consumption. Thus, the model described is suitable for hemodynamic and metabolic studies of the left ventricular myocardium with the working heart in situ.