[Diffusion capacity of the myocardial capillary bed in graded decrease in the coronary blood flow]

In closed chest dogs with controlled perfusion of the left coronary artery coronary blood flow was reduced by 10, 20, 30, 40, 50 and 70%. Diffusion capacity of myocardial capillary bed (permeability surface area product) decreased in all but the first (10%) series of experiments. 23-64% fall of the product occurred irrespective of coronary vessel reserve state but with respect to the degree of blood flow reduction. The amount of coronary influx possibly determined the number of perfused capillaries in the heart. Thus, 20% and more reduction of coronary blood flow cannot be compensated at the level of myocardial capillary bed.