Intracoronary vs Intravenous Abciximab for ST elevation MI
Abstract & Commentary
By Andrew J. Boyle, MBBS, PhD Dr. Boyle is Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco Dr. Boyle reports no financial relationships relevant to this field of study.
Source: Thiele H, et al. Intracoronary compared with intravenous bolus abciximab application in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention. Circulation. 2008;118:49-57.
Following successful reperfusion for acute myocardial infarction (MI) with primary percutaneous coronary intervention (PCI), the persistence of impaired perfusion portends a poor prognosis. Glycoprotein IIb/IIIa inhibitors improve microvascular perfusion, reduce infarct size, and improve clinical outcomes in primary PCI. However, despite the routine use of glycoprotein IIb/IIIa inhibitors, some patients still have impaired perfusion and, thus, there is a need for better strategies to improve outcomes in primary PCI. Intracoronary delivery of abciximab may result in higher local concentrations of the drug and may, therefore, reduce platelet thrombi and microemboli. Accordingly, Thiele et al conducted a single center, randomized study of intracoronary abciximab vs intravenous abciximab in patients undergoing primary PCI for acute ST elevation MI.
Thiele et al randomized 154 patients presenting with ST elevation MI to receive either intravenous (IV) (n = 77) or intracoronary (IC) (n = 77) abciximab. The primary outcomes were infarct size and microvascular obstruction by cardiac MRI. The baseline characteristics were similar between groups, and all patients received aspirin and heparin prior to PCI, with a loading dose of 600 mg of clopidogrel given during or after PCI. The intracoronary infusion of abciximab was given after the wire crossed the lesion, or after the PCI, and it was delivered over one minute. Time to reperfusion was similar between groups. In all patients, the abciximab bolus was followed by a 12-hour IV infusion. Cardiac MRI was performed two days after PCI.
Infarct size was smaller after IC abciximab vs IV abciximab (15.1% vs 23.4% of LV, p = 0.01). Microvascular obstruction was seen in 1.1% vs 3.4% of the LV, p = 0.01. These parameters were also reported in pre-defined subgroups, which showed the greatest benefit of IC abciximab inpatients with anterior MI, those presenting more than four hours after symptom onset and those with persistently impaired TIMI flow and perfusion grades after PCI. However, at this early time-point, there was no difference between groups in LV end-systolic volume, end-diastolic volume, or ejection fraction.
Thiele et al also studied a number of secondary endpoints. Enzymatic infarct size, calculated as the area under the curve of creatine kinase release, was smaller in the IC abciximab group; 575 vs 736 micromol/L/h, p = 0.007. ST segment resolution occurred in 77.8% of the IC group compared to 70.0% of the IV group, p = 0.006. There was no difference between groups in TIMI flow and perfusion grades. Major adverse cardiac events, defined as death, MI, target vessel revascularization, or new heart failure were recorded at 30 days post PCI, and occurred in 5.2% of patients receiving IC abciximab and 15.6% of those receiving IV abciximab, p = 0.06. Thiele et al conclude that IC abciximab is superior to standard IV abciximab in reducing infarct size and microvascular obstruction in patients undergoing primary PCI for ST elevation MI.
Commentary
It is not known whether any patients in this trial underwent thrombectomy prior to PCI, or how many patients had pre-dilatation before stenting. These factors could potentially influence the amount of embolization from the plaque and, therefore, the amount of microvascular obstruction and infarct size. Furthermore, no data is supplied as to the use of other adjunctive pharmacotherapy, such as IC adenosine or verapamil, which may also influence the amount of microvascular obstruction. However, this study utilized a very sensitive method to detect infarct size, microvascular obstruction, and cardiac MRI, and their primary endpoint is, therefore, robust. An adequately powered trial to assess the long-term effects of this approach on ventricular function, ventricular volumes, and reduction in major adverse cardiac events is warranted.
Following successful reperfusion for acute myocardial infarction (MI) with primary percutaneous coronary intervention (PCI), the persistence of impaired perfusion portends a poor prognosis.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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