Effect of systemic vasodilators on internal mammary artery flow: Implications for postoperative treatment after myocardial revascularization

Abstract

Postoperative spasm of the internal mammary artery graft can cause morbidity and mortality after myocardial revascularization. To our knowledge, the ability of systemic vasodilators to overcome internal mammary artery spasm has not been studied clinically. In 50 patients in whom the left internal mammary artery was used for myocardial revascularization, we have investigated the effect of five agents on internal mammary artery free flow: normal saline, dobutamine, glyceryl trinitrate, sodium nitroprusside, and enoximone, a phosphodiesterase III inhibitor. After the internal mammary artery was harvested, free flow was measured under controlled hemodynamic conditions before any pharmacologic intervention (flow 1) and a mean of 18.5 ± 3 (standard deviation) minutes after a systemic infusion of one of the five agents was begun (flow 2). The increase in free flow expressed as a percentage of initial flow was greater for enoximone (94% ± 24%) than for normal saline (18% ± 11%), dobutamine (40% ± 27%), and glyceryl trinitrate (52% ± 36%) (all three p < 0.01). The increase in flow for sodium nitroprusside (78% ± 37%) was greater than for normal saline and dobutamine (both p < 0.05). We therefore recommend the systemic use of enoximone and sodium nitroprusside, in rank order, to prevent and treat postoperative spasm of the internal mammary artery. (J THORACCARDIOVASCSURG1994;108:82-5)