Aims The aim of this study is to evaluate the usefulness of the index of microcirculatory resistance (IMR) for predicting myocardial viability and left ventricular (LV) function recovery in acute myocardial infarction (AMI). Methods and results After successful primary percutaneous coronary intervention in 40 patients with anterior AMI, IMR was measured using a pressure-temperature sensor-tipped coronary guidewire. Myocardial viability was quantified by 18Ffluorodeoxyglucose (FDG) positron

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... ion tomography in 38 patients. Echocardiographic regional wall motion was analysed to calculate the anterior wall motion score (A-WMS) and percent change in A-WMS after revascularization and at 6-month follow-up. IMR correlated significantly with regional myocardial FDG uptake (r ¼ 20.738, P , 0.001) and it demonstrated significant correlation with percent change in A-WMS (r ¼ 20.464, P ¼ 0.003). The area under the receiver operating curve of IMR for predicting LV function recovery was 0.89 [95% CI 0.888 -0.894]. Conclusion Index of microcirculatory resistance, a new index representing microvascular integrity, is a reliable early on-site determinant of myocardial viability and LV recovery after primary stenting for AMI. --- Keywords Myocardial viability † Acute myocardial infarction † Microvascular integrity † Index of microcirculatory resistance † FDG PET