PHENTOLAMINE PREVENTS ADAPTATION TO ISCHEMIA DURING CORONARY ANGIOPLASTY - ROLE OF ALPHA-ADRENERGIC RECEPTORS IN ISCHEMIC PRECONDITIONING

Background Experimental studies indicate that alpha-adrenergic recepto rs are involved in ischemic preconditioning. Their role in humans is u nknown. Methods and Results Eighteen patients undergoing angioplasty f or an isolated stenosis of the left anterior descending coronary arter y were randomized to receive intravenous infusion of phentolamine or p lacebo during the procedure. Intracoronary ECG and cardiac pain were d etermined at the end of the first two balloon inflations. Average peak velocity in the contralateral coronary artery during balloon occlusio n, an index of collateral recruitment, was also assessed by using a Do ppler guide wire. In both phentolamine-and placebo-treated patients, a verage peak velocity significantly increased from baseline to the end of the first inflation (P < .01), but it did not show any further incr ease during the second inflation. In phentolamine-treated patients, ST -segment changes and car diac pain severity during the second inflatio n were similar to those observed during the first inflation (13 +/- 9 versus 12 +/- 8 mm, P = NS, and 51 +/- 34 versus 54 +/- 32 mm, P = NS, respectively), whereas in placebo-treated patients, they were signifi cantly less (6 +/- 4 versus 13 +/- 7 mm, P < .01, and 26 +/- 20 versus 49 +/- 22 mm, P < .05, respectively). Conclusions The adaptation to i schemia observed in humans after two sequential coronary balloon infla tions is abolished by phentolamine and is independent of collateral re cruitment. Thus, it occurs due to ischemic preconditioning and is, at least in part, mediated by alpha-adrenergic receptors.