Impact of Coronary Microvascular Resistance Index Immediately After Primary Percutaneous Coronary Intervention on Myocardial Viability in Acute Myocardial Infarction
Wakayama Medical University, Wakayama, Japan
H. Kitabata, M. Kashiwagi, H. Matsumoto, H. Ikejima, Y. Arita, K. Okochi, H. Tsujioka, A. Kuroi, S. Ueno, H. Kataiwa, T. Tanimoto, T. Yamano, S. Takarada, T. Kubo, N. Nakamura, K. Hirata, A. Tanaka, M. Mizukoshi, T. Imanishi, T. Akasaka
Background: The degree of coronary microvascular damage after reperfusion is an important determinant of myocardial viability and clinical outcomes in patients with acute myocardial infarction (AMI). However, a simple and useful method for assessing coronary microcirculation has not been fully elucidated. A novel 0.014-inch dual-sensor (pressure and Doppler velocity) guidewire has an ability to estimate coronary microvascular resistance. Contrast-enhanced MRI can differenciate non-transmural MI (viable) from transmural MI (non-viable). The aim of this study was to assess the relationship between coronary microvascular resistance index (MVRI) immediately after primary percutaneous coronary intervention (PCI) and myocardial viability in patients with AMI.
Methods: We enrolled 27 patients (22 men, mean age 65¡¾11years ) who underwent primary PCI for a first anterior AMI within 12 hours from the onset of symptoms. Immediately after primary PCI, a 0.014-inch dual-sensor guidewire was placed distal to the culprit lesion to take per-beat averages of pressure and flow velocity simultaneously. MVRI was determined as the ratio of mean distal pressure to average peak flow velocity during maximal hyperemia. Peak creatine kinase MB (CK-MB) fraction values were derived from serial CK-MB measurements. Delayed contrast-enhanced MRI (DeMRI) was also performed in all patients 2 weeks after the onset of AMI. Using a 17-segment model, the transmural extent of infarction (TEI) by DeMRI was graded from 1 to 4 based on the extent of hyperenhanced tissue ( grade 1 = 0 to 25% of hyperenhanced extent of left ventricular (LV) wall, grade 2 = 26 to 50%, grade 3 = 51 to 75% and grade 4 = 76 to 100%). The highest grade among 16 segments except LV apex was defined as the TEI-grade of each case. Infarct size by MRI was defined as follows: (volume of enhanced tissue ¥Ö 100 / total volume of LV myocardium)(%).
Results: The average time from symptom onset to the evaluation of coronary microcirculation was 4.9¡¾2.1 hours. A significant positive correlation was observed between MVRI and the TEI-grade (P<0.0002). Futhermore, MVRI was strongly correlated with peak CK-MB value (r = 0.77, P<0.0003) and infarct size by MRI (r = 0.80, P<0.0004). The best cut-off value of MVRI for the prediction of transmural MI (TEI-grade 4) was 3.2 mmHg･cm-1･s (sensitivity 100%, specificity 88.9%, positive predictive value 75%, and negative predictive value 100%).
Conclusion: MVRI immediately after primary PCI is a useful coronary physiologic parameter for predicting myocardial viability in patients with AMI.
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