Abstract 3338: Value of a Novel Index of Microcirculatory Resistance for Invasively Assessing Myocardial Viability After Primary Angioplasty in Acute Myocardial Infarction: Comparison With FDG-PET

Abstract

Background: Despite the prognostic importance of the status of coronary microcirculation, there has been lacking in comparative studies on the most reliable invasive measurement for assessing microvascular integrity and myocardial viability in AMI. We compared a novel Index of Microcirculatory Resistance(IMR) to intracoronary wire-based physiologic parameters for evaluating myocardial viability after primary percutaneous coronary intervention(PCI) in AMI. Methods: After successful primary stenting for 28 patients with AMI, Doppler-derived microvascular resistance index (MVRI) and phasic flow velocity patterns were evaluated. Using a pressure-temperature sensor-tipped coronary wire, thermodilution-derived CFR(CFR thermo ) and coronary wedge pressure(P cw ) were measured and the ratio of P cw and mean aortic pressure(P cw /P a ) was calculated, along with IMR, defined as the distal coronary pressure divided by the inverse of the hyperemic mean transit time. 18 F-fluorodeoxyglucose(FDG) PET was performed after primary PCI to evaluate myocardial viability by regional percentage uptake of FDG in infarct-related segments. Results: Among Doppler-derived parameters, regional FDG uptake showed nice correlation with hyperemic averaged peak velocity(r=0.561, p=0.002), hyperemic MVRI (r= −0.452, p=0.016) and baseline deceleration time of diastolic flow velocity (r=0.505, p=0.006). In the group of pressure-derived parameters CFR thermo , P cw /P a and IMR revealed good correlations with regional FDG uptake (r=0.487, p=0.016; r= −0.469, p=0.012; r= −0.656, p<0.001, respectively). By the receiver operating characteristics curve analysis for prediction of myocardial viability, as defined by the 50% FDG-PET threshold value, the largest area under the curve was acquired by IMR and the best cut-off value of IMR for prediction of myocardial viability was 22U (sensitivity of 79%, specificity of 86% and accuracy of 81%). Conclusions: Wire-based coronary physiologic assessment is useful for the prediction of myocardial viability immediately after primary PCI. IMR, a novel index representing the microvascular integrity, is a reliable parameter for the invasive, on-site assessment of myocardial viability after primary PCI in AMI.