Coronary Microvascular Resistance Index Immediately After Primary Percutaneous Coronary Intervention as a Predictor of the Transmural Extent of Infarction in Patients With ST-Segment Elevation Anterior Acute Myocardial Infarction

OBJECTIVES The purpose of this study was to investigate whether microvascular resistance index (MVRI) immediately after primary percutaneous coronary intervention (PCI) can predict the transmural extent of infarction (TEI) defined by contrast-enhanced cardiac magnetic resonance (ce-CMR) in patients with anterior acute myocardial infarction (MI). BACKGROUND The degree of microvascular damage is an important determinant of myocardial viability and clinical outcomes in acute MI. A novel dual-sensor (pressure and Doppler velocity) guidewire has the ability to evaluate microvascular damage. ce-CMR can accurately discriminate transmural from nontransmural MI, and the TEI by ce-CMR can predict future improvement in contractile function. METHODS In 27 patients immediately after primary PCI for a first anterior acute MI, MVRI, coronary flow reserve (CFR), deceleration time of diastolic velocity (DDT), and zero flow pressure (Pzf) were measured with a dual-sensor guidewire. TEI was graded from 1 to 4 based on the transmural extent of hyperenhanced tissue (1 = 0% to 25% of left ventricular wall thickness, 2 = 26% to 50%, 3 = 51% to 75%, and 4 = 76% to 100%). Infarct size by ce-CMR was also calculated. RESULTS Peak creatine kinase-myocardial band values were significantly correlated with MVRI (r = 0.77, p < 0.0001), CFR (r = -0.69, p < 0.0001), DDT (r = -0.75, p = 0.0001), and Pzf (r = 0.75, p < 0.0001). Also, infarct size by ce-CMR was significantly correlated with MVRI (r = 0.78, p < 0.0001), CFR (r = -0.67, p < 0.0001), DDT (r = -0.70, p < 0.0001), and Pzf (r = 0.72, p = 0.0002). Receiver-operating characteristic curve analyses of MVRI, CFR, DDT, and Pzf for predicting transmural MI (TEI-grade 4) demonstrated that the area under the curve tended to be higher for MVRI (0.885) than those for CFR (0.848), DDT (0.862), and Pzf (0.853). The best cut-off value for MVRI was 3.25 mm Hg.cm(-1.)s (sensitivity 75%, specificity 89%). Moreover, increased MVRI was significantly related to increased TEI-grade (p < 0.0001). CONCLUSIONS MVRI measured immediately after primary PCI is a useful predictor for the TEI in patients with anterior acute MI. (J Am Coll Cardiol Img 2009;2:263-72) (C) 2009 by the American College of Cardiology Foundation