Preparation of the internal thoracic artery by vasodilator drugs: is it really necessary? A randomized double-blind placebo-controlled clinical study.

Abstract

The internal thoracic artery has become the conduit of choice for coronary artery bypass grafting. To avoid spasm of the artery, and increases in its diameter and flow, various vasodilators have been used either intraluminally or by topical application by different surgeons. In order to define the best vasodilating agent for preparation of the internal thoracic artery, a randomized double-blind placebo-controlled clinical study was performed in a group of patients submitted for elective coronary artery bypass grafting. Eighty (80) consecutive patients submitted for elective first time coronary artery bypass grafting were randomly subdivided into five treatment groups. Free flow of the left internal thoracic artery was measured using an electromagnetic flow meter. The first measurement was performed shortly after the internal thoracic artery was dissected from the chest wall and the second just prior to performing distal anastomosis to the left anterior descending coronary artery. During the time interval between the two measurements the internal thoracic artery was immersed in a special applicator tube containing 20 ml solution of one of the following drugs: papaverin 2 mg/ml, nitroglycerin 1 mg/ml, verapamil 0.5 mg/ml, nitroprusside 0.5 mg/ml, normal saline 0.9%. No statistically significant differences were found between the groups in respect to age, body surface area, bypass time, cross clamping time, and time interval between the two flow measurements. Mean arterial pressure at the time of the first and second internal thoracic artery flow measurements did not show statistically significant differences either within or between the groups. In all five groups, the free flow of the internal thoracic artery increased significantly with time. However, no statistically significant differences were shown between the five groups with respect to second flow (P = 0.2). Within the limits of our study design, we suggest that preparation of the LITA by topical vasodilator drugs using a special applicator tube does not result in a significantly superior free flow than placebo.