DILATION OF THE INTERNAL MAMMARY ARTERY BY EXTERNAL AND INTRALUMINAL PAPAVERINE APPLICATION

Three methods for prevention of perioperative spasm for the internal m ammary artery were compared in 78 patients undergoing coronary artery bypass grafting. In group 1, internal mammmary artery pedicles were di vided distally, clamped, and placed under the upper sternum submerged in papaverine solution (1.5 mg/ml). In group 2, as in group 1 but befo re clamping, 2 ml of heparinized blood with 1.5 mg/ml papaverine added was injected into the bessel lumen. In group 3 treatment was as in gr oup 2, but heparinized blood with papaverine was injected a second tim e just before extracorporeal bypass was begun. In a univariate analysi s free flow from dilated internal mammary arteries was not significant ly different among the groups (group 1, 58 ml/min; group 2, 82 ml/min; group 3, 68 ml/min; p < 0.1), When free flow from dilated internal ma mmary arteries was the dependent variable in a regression analysis, th e use of intraluminal papaverine, high blood pressure during flow meas urement, and high initial blood flow were predictors of high flow (all p < 0.01), Morphometric measurements on the resected distal portion o f the dilated internal mammary arteries disclosed less folding of the internal elastic lamina and a larger luminal area in groups 2 and 3 co mpared with respective findings in group 1 (1.21 mm(2) and 1.42 mm(2) versus 0.77 mm(2); p < 0.02). Mechanical vessel wall injury occurred i n 8 of 52 internal mammary arteries treated with intraluminal papaveri ne. Intraluminal papaverine solution injected once or twice in additio n to external papaverine exposure therefore provides a better blood fl ow rate and distal dilation than mere submersion in papaverine solutio n, but at a considerable risk of mechanical wall injury.