BackgroundVasoconstriction occurs after percutaneous transluminal coronary angioplasty (PTCA) along the dilated vessel. The vasomotor changes, initiated by the mechanical stretch of the stenotic region, are thought to be due to various mechanisms but whether the sympathetic nervous system plays a role in this phenomenon remains unknown.Methods and ResultsQuantitative angiography (ARTREK) was performed in 45 patients undergoing an epicardial vessel PTCA for a stenosis of 76±1% (1) in basal conditions, (2) after PTCA, and (3) 30 minutes after PTCA (vasoconstriction). In 14 control patients, the same measurements were obtained up to 60 minutes after PTCA. Coronary diameters were measured along the PTCA vessel at the narrowest stenosis level and at a level peripheral to stenosis. In 36 patients two diameters were also measured at a proximal segment and at a distal segment along a nonmanipulated vessel.Thirty minutes after PTCA the dilated segment under-went a −31±2% (mean±SEM, ANOVA,P<.05) reduction in diameter when compared with PTCA values, and the segment peripheral to stenosis showed a reduction of −17±2% (P<.05).In all patients a significant vasoconstriction also was observed along the control vessel (proximal segment, −14±3%;P<.05 versus basal; and distal segment, −17±2%). At the time of maximal vasoconstriction (30 minutes after PTCA), the patients (treatment groups) received (1) 18 μg/kg IC phentolamine (Phe, n=7), (2) 14 μg/kg IC yohimbine (YO, n=7), (3) 16 μg/kg IC propranolol (Pro) followed by 18 μg/kg IC phentolamine (Pro+Phe, n=7), and (4) 0.2 μg/kg IC bretylium (Bre, n=10). In 14 patients (control groups) an intracoronary injection of warm saline was given. After drug injections, angiograms were repeated at 5-minute intervals for 20 minutes and ended after a 300-μg intracoronary trinitro-glycerin injection. At stenosis level, Phe and Bre counteracted vasoconstriction, inducing a dilatation of +19±3% and +22±6%, respectively, while Pro+Phe caused a dilatation of +16±9% above the PTCA values (P<.05 versus PTCA). YO only partially reversed vasoconstriction (from −33±4% to −12±4%,P=NS versus PTCA). At peripheral-to-stenosis level, vasoconstriction was abolished by Phe (+26±7%,P<.05 versus basal), while it was still present after Pro+Phe (−23±2%) and Bre (−18±4%). In addition, Phe and Bre dilated the control vessel at the proximal segment (+17±6% and +8±4%, respectively,P<.05 versus basal), while YO and Pro+Phe only counteracted vasoconstriction (from −15 ±3% to +7.6±1% and from −16±3% to +4±5%, respectively,P=NS versus basal). At the distal segment only Phe produced a vasodilatation of +23±1%; YO counteracted constriction (from −16±2% to +9±6%,P<.05 versus basal), whereas after Pro+Phe and Bre, the vasoconstriction persisted.ConclusionsThe mechanical stretch and ischemia caused by balloon inflation induced vasoconstriction mediated by a-adrenergic receptors (mainly α1,), overcoming a β-mediated dilatation. The use of different antiadrenergic drugs showed that Phe counteracts post-PTCA vasoconstriction, and the simultaneous use of α- and β-receptor blocking agents (Pro+Phe and Bre) reveals the presence of a peripheral, predominant β-mediated dilatation. The presence of vasoconstriction also along the control vessels not branching from the stretched ramus provides evidence for the existence of neural sympathetic vasoconstrictor reflexes.