Bradykinin-induced preconditioning in patients undergoing coronary angioplasty

OBJECTIVES The purpose of this study was to determine whether administration of bradykinin reproduces the cardioprotective effects of ischemic preconditioning (PC) in patients undergoing percutaneous transluminal coronary angioplasty (PTCA). BACKGROUND Experimental studies suggest that activation of the bradykinin B2 receptor is an important trigger of ischemic PC. However, it is unknown whether bradykinin can precondition human myocardium against ischemi in vivo. Multicenter clinical trials have demonstrated an anti-ischemic effect of angiotensin-converting enzyme inhibitors, which has been postulated to result from potentiation of bradykinin; however, direct evidence for an anti-ischemic action of bradykinin in patients is lacking. METHODS Thirty patients were randomized to receive 10-min intracoronary infusion of bradykinin (2.5 μg/min) or normal saline. Ten minutes later they underwent PTC (three 2-min balloon inflations 5 min apart). RESULTS In control patients, the ST-segment shift on the intracoronary and surface electrocardiogram was significantly greater during the first inflation than during the second and third inflations, consistent with ischemic PC. In bradykinin-treated patients, the ST-segment shift during the first inflation was significantly smaller than in the control group, and there were no appreciable differences in ST-segment shift during the three inflations. Measurements of chest pain score and regional wall motion during inflation (quantitative two-dimensional echocardiography) paralleled those of ST-segment shift. Infusion of bradykinin had no hemodynamic effects and no significant adverse effects. Thus, intracoronary infusion of bradykinin before PTC rendered the myocardium relatively resistant to subsequent ischemia, and the degree of this cardioprotective effect was comparable to that afforded by the ischemi associated with the first balloon inflation in control subjects. In separate cohort of seven patients given the same dose of bradykinin, coronary hyperemi resolved completely within 10 min after the end of the infusion, indicating that bradykinin-induced vasodilation cannot account for the protective effects observed during the first balloon inflation. CONCLUSIONS Bradykinin preconditions human myocardium against ischemi in vivo in the absence of systemic hemodynamic changes. Pretreatment with bradykinin appears to be just as effective as ischemic PC and could be used prophylactically to attenuate ischemi in selected patients undergoing PTCA.