Purpose <p>We conducted a prospective interventional before-after study to evaluate the effect of left stellate ganglion block on left internal mammary artery diameter and blood flow in patients undergoing myocardial revascularization surgery. The aim was to assess the change in left internal mammary artery diameter and blood flow by ultrasound before and after left stellate ganglion block.</p> Methods <p>In 45 patients undergoing coronary artery bypass grafting surgery, left stellate ganglion block was given under ultrasonographic guidance with 10&#xa0;ml of 0.25% bupivacaine. Left internal mammary artery diameter and velocity time integral were measured using ultrasonography, and compared before and 20&#xa0;min after the block at the level of the 2nd or 3rd rib. Heart rate (HR), systolic, diastolic, and mean arterial blood pressures were recorded before and 20&#xa0;min after the block. Inadequacy of left internal mammary artery flow, demonstrable by electrocardiographic changes, regional wall motion abnormalities, or angiographically if indicated postoperatively, was recorded. Incidence of in-hospital mortality and significant cardiac arrhythmias were also noted.</p> Results <p>There was a statistically significant increase in the left internal mammary artery diameter and blood flow before and after left stellate ganglion block and a decrease in HR, systolic, diastolic, and mean arterial blood pressures. The frequency and percentage of significant cardiac arrhythmias in the intra- and postoperative periods was 6 (13.3%).</p> Conclusions <p>Ultrasound-guided left stellate ganglion block consistently increased left internal mammary artery diameter and blood flow in patients undergoing myocardial revascularization.</p> <p>Central figure </p>