Effect of topical vasodilators on internal mammary arteries

The internal mammary artery (IMA) is the conduit of choice for grafting the left anterior descending artery. However, arterial spasm and reduced early flow has been a cause of postoperative morbidity. The purpose of this study is to evaluate the effect of vasodilators on IMA flow. Fifty patients who had the IMA harvested in preparation for bypass grafting were studied. The IMA was mobilized from the subclavian vein to below the bifurcation of the IMA. The artery was prepared for grafting at least 3 cm proximal to the bifurcation. The IMA was allowed to bleed freely, and flow was determined (flow 1). The patients were divided into five groups: group I (n = 10) had 10 mL of saline solution applied topically to the IMA; group II had topical papaverine (5 mg/10 mL normal saline solution) applied to the IMA; group III had nitroglycerin (5 mg/10 mL normal saline solution) applied to the IMA, group IV had sodium nitroprusside (2.5 mg/10 mL) applied to the pedicle, and group V had 5 mL of papaverine mixed in 5 mL of saline solution injected into the periarterial tissues of the IMA pedicle. Before cardiopulmonary bypass, the flows were remeasured (flow 2). With each measurement, hemodynamic parameters were recorded. The time between measurements was recorded. There was no difference in blood pressure or pulse at the time of measurement. Each group showed a significant increase in flow from flow 1 to flow 2 (group I, 59 ± 20.7 versus 72.8 ± 17 mL/min, p = 0.035; group II, 85.5 ± 25.4 versus 118.5 ± 53 mL/min, p = 0.014; group III, 70.55 ± 24.4 versus 90.1 ± 30.1 mL/min, p = 0.014; group IV, 43.0 ± 27.2 versus 67.2 ± 27.38 mL/min, p = 0.044; and group V, 57.6 ± 33.3 versus 83.2 ± 48.9 mL/min, p = 0.029). Comparing the increase in IMA flow between the groups from flow 1 to flow 2, there were no differences in the absolute increase of flow ( p = 0.836) or in the percent change from baseline ( p = 0.896). After the IMA was prepared for grafting, there was a reduction in flow that resolved with time. Thus, if the artery is fashioned proximally and has adequate early flow (>40 mL/min), topical vasodilators are not warranted.