ASSESSMENT OF INTERNAL THORACIC ARTERY VASOREACTIVITY IN RESPONSE TO SUBLINGUAL NITROGLYCERIN

Background. We have previously shown the feasibility of assessing inte rnal thoracic artery (ITA) size and blood now hemodynamics before and after coronary artery bypass grafting using color-flow duplex ultrasou nd. This noninvasive method would be an ideal diagnostic tool for the evaluation of ITA graft status after therapeutic interventions in a pa tient with angina after coronary artery bypass grafting. The purpose o f this study was to investigate the effects of nitroglycerin on the di ameter and blood flow velocities of the left native ITA before coronar y artery bypass grafting and the ITA graft postoperatively. Methods. T he study consisted of 24 male patients (mean age, 59 +/- 2.3 years) wh o had undergone elective coronary artery bypass grafting using a left ITA graft to the left anterior descending artery, with additional saph enous vein grafts. Color-flow duplex ultrasound (5.0-MHz transducer) w as used for both the preoperative imaging of native ITAs and the posto perative study of ITA grafts before patient discharge. Repeated-measur es analysis of variance was used to compare measurements of the ITA si ze and flow velocities (peak systolic velocity and end-diastolic veloc ity) at 5, 10, and 15 minutes after a single dose of sublingual nitrog lycerin (0.4 mg) with the baseline values obtained without nitroglycer in. Results. The preoperative native left ITA and the postoperative le ft ITA graft diameters responded to sublingual nitroglycerin by showin g a rapid and significant increase beginning at 5 minutes and lasting up to 15 minutes (p = 0.0001). Sublingual nitroglycerin caused the pea k systolic velocity of the native left ITA to be augmented at 5 minute s (p = 0.0002), and this effect was still apparent at 10 minutes (p = 0.0001) and 15 minutes (p = 0.0192). However, postoperative left ITA g raft peak systolic velocities remained unaffected by the sublingual ni troglycerin (p = not significant). Conclusions. We conclude that insta ntaneous noninvasive measurement of ITA graft size and blood flow velo cities after a therapeutic drug intervention may be clinically useful, particularly in a post-coronary artery bypass grafting patient with r ecurrent angina. (C) 1997 by The Society of Thoracic Surgeons.