['Perioperative internal mammary artery (IMA) vasospasm in patients undergoing coronary artery bypass grafting (CABG) surgery may lead to morbidity and mortality. Surgical stimulus is one of the common causes of IMA vasospasm. Preventive measures, beside treatment should be taken into consideration to obtain vasospasm free IMA. The effect of a pharmacologic agent on IMA flow when it is administered before harvesting the artery has not been documented. We designed a prospective randomized clinical study to compare the IMA free blood flows in patients receiving either diltiazem or nitroglycerin, starting infusion of study drugs before a surgical stimulus was applied to the IMA region and continuing throughout the isolation period.', "Sixty patients undergoing elective CABG surgery with the left IMA received diltiazem (n=30, 0.05-0.1 mg/kg per hour) or nitroglycerin (n=30, 0.25-2.5 microg/kg per minute) in a randomized manner. Infusions of study drugs were started before applying a surgical stimulus to the IMA region and continued throughout the harvesting period. The first free flow was measured after IMA was cut above its bifurcation and the second after its distal segment was resected. Heart rate, temperature, mean arterial and central venous pressures were recorded. Data were analyzed with Student's t-test and Fischer's exact test.", 'Preoperative and hemodynamic data were similar between the groups. The means of first and second IMA flows in patients treated with diltiazem (53.8+/-30.1 and 72.3+/-35.4 ml/min) were significantly higher than in those treated with nitroglycerin (25.7+/-16.2 and 48.9+/-23.8 ml/min; P=0.000, 0.004, respectively). IMA flows significantly increased after distal segment resection both in diltiazem (34%) and nitroglycerin groups (90%; P= 0.000, 0.000, respectively).'] Does diltiazem provide higher internal mammary artery flow than nitroglycerin during coronary artery bypass grafting surgery?