Intravenous β-blockers in primary percutaneous coronary intervention: new hope for an old therapy.

P rimary percutaneous coronary intervention (PCI) is the preferred strategy of reperfusion for patients with ST-segment–elevation myocardial infarction (STEMI). With contemporary PCI techniques and adjunctive pharmacological therapy, primary PCI restores optimal epicardial flow in as many as 95% of patients with STEMI. 1 However despite remarkable improvement in the outcomes of patients with STEMI, mortality and morbidity remain significant. 2 To further improve the efficacy of reperfusion, considerable efforts are being made on 2 fronts: the development of systems to provide timely access to PCI for patients with STEMI to reduce time to reperfusion 3 and the investigation of therapies to minimize reperfusion injury (ie, to render myocardial cells more resistant to the detrimental effects of the ischemia/reper-fusion cycle). 4 The restoration of blood flow to the ischemic myocardium is associated with reperfusion injury manifested as myocardial stunning, no reflow, arrhythmias, and myocar-dial hemorrhage. Experimental studies in animals suggest that reperfusion injury may account for up to 50% of the final infarct size. 5 Despite decades of research, an understanding of reperfusion injury remains elusive, and remarkably little success has been achieved with translational research in cardio-protective therapeutics. 6 Article see p 1495 β-Blockers have long been a component of care in patients with acute myocardial infarction because of their ability to reduce myocardial oxygen consumption by reducing heart rate and myocardial contractility. Preclinical studies showed reduced infarct size in dogs, particularly when the β-blockers are administered before coronary artery ligation. 7 Several clinical studies performed in the prereperfusion era have demonstrated beneficial effects of β-blockers in acute myocardial infarction in terms of reduction of infarct size 8,9 or improved survival. Conversely, in the thrombolytic era, random-ized studies involving early intravenous administration of β-blockers were largely disappointing, with no improvement in left ventricular function, infarct size, or mortality. Moreover, the large-scale Clopidogrel and Metoprolol in Myocardial Infarction Trial (COMMIT) showed not only no favorable effect of β-blockade on death resulting from any cause or the composite of death, reinfarction, or cardiac arrest but also a significant increase in the incidence of cardiogenic shock. 14 This further dampened enthusiasm for the early use of β-blockers in patients with acute myocardial infarction, at least in the setting of thrombolysis. In patients with STEMI undergoing primary PCI, several observational studies or post hoc analyses showed that preprocedural β-blockade was associated with significant improvement in clinical outcome, including reduced short-term mortality. However, studies that …