Phentolamine Prevents Adaptation to Ischemia During Coronary Angioplasty

Abstract

Background Experimental studies indicate that α-adrenergic receptors are involved in ischemic preconditioning. Their role in humans is unknown. Methods and Results Eighteen patients undergoing angioplasty for an isolated stenosis of the left anterior descending coronary artery were randomized to receive intravenous infusion of phentolamine or placebo during the procedure. Intracoronary ECG and cardiac pain were determined at the end of the first two balloon inflations. Average peak velocity in the contralateral coronary artery during balloon occlusion, an index of collateral recruitment, was also assessed by using a Doppler guide wire. In both phentolamine- and placebo-treated patients, average peak velocity significantly increased from baseline to the end of the first inflation ( P <.01), but it did not show any further increase during the second inflation. In phentolamine-treated patients, ST-segment changes and cardiac pain severity during the second inflation 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 significantly less (6±4 versus 13±7 mm, P <.01, and 26±20 versus 49±22 mm, P <.05, respectively). Conclusions The adaptation to ischemia observed in humans after two sequential coronary balloon inflations is abolished by phentolamine and is independent of collateral recruitment. Thus, it occurs due to ischemic preconditioning and is, at least in part, mediated by α-adrenergic receptors.