Hemodynamic effects of long and multiple coronary arterial narrowings.

The coronary hemodynamic influence of a series of coronary arterial narrowings was compared with single narrowings of the same total length and reduction in diameter in 12 dogs. Compared with single narrowings, two or three sequential narrowings had no significant effect on restng coronary blood flow. Small but significant mean pressure gradients were found for series of two and three 1-mm narrowings but not for single narrowings of the same total length. During reactive hyperemia, repayment of the debt in flow decreased significantly for single 2-mm and 3-mm narrowings, compared with 1-mm single narrowings. An additional decrease in repayment of the debt in flow occurred for two and three separate narrowings, compared with single narrowings. Our findings imply that when the reduction in the diameter of the coronary artery is fixed, an increase in the length or number of narrowings in series reduces the responses of coronary blood flow during reactive hyperemia.