Abstract 902: Coronary Microvascular Resistance Index Measured Immediately after Primary Percutaneous Coronary Intervention Predicts the Transmural Extent of Infarction in Patients with ST-Elevation Anterior Acute Myocardial Infarction
Background: The degree of microvascular damage is an important determinant of myocardial viability and clinical outcomes in acute myocardial infarction (AMI). A novel dual-sensor (pressure and Doppler velocity) guidewire has an ability to evaluate microvascular damage using various indices such as microvascular resistance index (MVRI), coronary flow reserve (CFR), diastolic deceleration time (DDT), and zero flow pressure (Pzf). Myocardial necrosis after AMI progresses as “wavefront phenomenon” from the endocardium to the epicardium. Contrast-enhanced magnetic resonance imaging (Ce-MRI) can accurately discriminate trans-mural from non-transmural MI, and the transmural extent of infarction (TEI) by Ce-MRI predicts improvement in contractile function. The aim of this study was to examine whether MVRI immediately after primary PCI can predict the TEI in patients with anterior AMI.
Methods: In 27 patients immediately after primary PCI for a first anterior AMI, using a dual-sensor guidewire, MVRI was calculated as the ratio of mean distal pressure to average peak flow velocity during maximal hyperemia. CFR, DDT, and Pzf were also measured. TEI by Ce-MRI was graded from 1 to 4 based on the trasmural extent of hyperenhanced tissue; 1=0 to 25%, 2 = 26 to 50%, 3 = 51 to 75%, and 4 = 76 to 100%). Infarct size (%) by Ce-MRI was also calculated.
Results: Peak creatine kinase-MB was 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), respectively. Also, infarct size by MRI 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), respectively. Receiver-operating-characteristic curve analyses of MVRI, CFR, DDT, and Pzf for the prediction of transmural MI (grade 4) demonstrated that the area under the curve was higher for MVRI (0.885) compared with those for CFR (0.848), DDT (0.862), and Pzf (0.853). The best cut-off value for MVRI was 3.25 mmHg·cm-1·s (sensitivity 75%, specificity 89%). Moreover, increased MVRI was significantly related to increased TEI-grade (P<0.0001).
Conclusion: MVRI measured immediately after primary PCI is a simple and useful predictor for the TEI in patients with anterior AMI.