Effects of nitroglycerin infusion on segmental wall motion abnormalities after anesthetic induction

Abstract

To assess the effect of intravenous nitroglycerin (NTG) on segmental wall motion abnormalities (SWMAs) and global ventricular function after anesthetic induction in patients undergoing coronary artery bypass grafting (CABG). Prospective study. University hospital. Twenty patients scheduled for elective CABG. Patients demonstrating SWMAs in at least two myocardial segments after induction received intravenous NTG at 2 micrograms/kg/min. Transesophageal echocardiography (TEE) was performed before and after the NTG infusion for analysis of segmental wall motion abnormalities. Mean arterial pressure (MAP), central venous pressure, and pulmonary capillary wedge pressure decreased significantly after NTG infusion, whereas cardiac index and heart rate remained unchanged. End-diastolic area and end-systolic area decreased, and consequently fractional area change increased significantly. Two of 20 patients (10%) showed electrocardiogram evidence of ischemia after induction. After NTG infusion, 15 of 20 patients (75%) showed an increase in a wall motion score more than two points. In these 15 patients with NTG-responsive wall motion abnormalities, the mean ratio of peak early diastolic filling velocity (E) to peak late diastolic filling velocity (A) increased from 0.89 +/- 0.20 to 1.04 +/- 0.25 (p < 0.01) after NTG infusion despite a decrease in filling pressure. Systolic wall thickening improved in segments with poor preoperative function from a pre-NTG value (mean +/- SD) of -1.0% +/- 7.4% to a post-NTG value of 31.4% +/- 24.9% (p < 0.01). Intravenous NTG improved postinduction SWMAs in 75% of patients with known coronary artery disease. TEE-guided NTG infusion after induction may provide an optimal baseline echocardiogram for monitoring intraoperative myocardial ischemia by improving the reversible portion of postinduction SWMAs.