Abstract
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Objectives Coronary stenoses are typically graded by visual estimation,although it is known that lumen assessment correlates poorly with physiological measures of ischaemia.FFR is a well-validated invasive method used for the evaluation of intermediate stenosis.The aim of this study was to compare FFR and 13NH3-PET myocardial perfusion and myocardial flow reserve (MFR) measurements.
Methods Five patients (pts) with CAD and a 50% to 75% coronary stenosis underwent quantitative NH3 PET.Cardiac scans were performed on an integrated whole-body 3T PET/MR.The NH3 injection was performed as slow bolus over 30 sec.PET data was acquired in list-mode for 15 min and attenuation correction was based on tissue segmentation of Dixon-based MR images acquired prior to the perfusion scans.At the same day all pts underwent invasive coronary angiography (ICA) and FFR measurement, and the treatment decisions were based on ICA and FFR.The pts individual vessel supply territory was delineated on the PET flow polar map by visually analyzing the ICA in at least two views by two cardiologists who were blinded to the noninvasive results.Pathologic threshold of 0.8 for FFR and 2.0 for MFR were used.
Results FFR was measured in 7 vessels and was assessed as pathologic in 4 territories with a mean FFR of 0.49 ± 0.14 and normal in 3 territories with a mean FFR of 0.90 ± 0.04.Mean resting perfusion for PET was 1.09 ± 0.29 ml/min/g and increased under stress conditions to 1.62 ± 0.45 ml/min/g.This increase in myocardial perfusion yielded a MFR of PET ranging from 1.1 to 1.9 (mean 1.5 ± 0.3).Using linear correlation analysis,close agreement was found between FFR and MFR by PET (R2=0.70).
Conclusions The study compared PET with an invasive functional assessment (FFR) and demonstrated that PET and FFR were in good agreement and both are able to distinguish haemodynamically relevant from non-relevant coronary lesions.