Diagnostic Value of PET-Measured Longitudinal Flow Gradient for the Identification of Coronary Artery Disease

OBJECTIVES The purpose of this study was to evaluate the diagnostic value of a positron emission tomography (PET)/computed tomography (CT)-determined longitudinal decrease in myocardial blood flow (MBF) gradient during hyperemia and myocardial flow reserve (MFR) for the identification of epicardial stenosis >= 50% BACKGROUND Although PET-determined reductions in MFR are increasingly applied to identify epicardial lesions in coronary artery disease (CAD), it may be seen as a suboptimal approach due to the nonspecific origin of decreases in MFR. METHODS In 24 patients with suspected or known CAD, MBF was measured with N-13-ammonia and PET/CT in rnl/g/min at rest, during dipyridamole stimulation, and the corresponding MFR was calculated. MBF was also determined in the mid and mid-distal myocardium of the left ventricle (LV). A decrease in MBF from mid to mid-distal LV myocardium was defined as longitudinal MBF gradient. MBF parameters were determined in the myocardial region with stress-induced perfusion defect and with stenosis >= 50% (territory 1), without defect but with stenosis >= 50% (territory 2), or without stenosis.50% (territory 3). RESULTS In territories 1 and 2 with focal stenosis.50%, the severity of epicardial artery stenosis correlated with the Delta longitudinal MBF gradient (stress-rest) (r = 0.52; p < 0.0001), while this association was less pronounced for corresponding MFR (r = -0.40; p < 0.003). On a vessel-based analysis, the sensitivity and specificity of the Alongitudinal MBF gradient in the identification of epicardial lesions was higher than those for MFR (88% vs. 71%, p <= 0.044; and 81% vs. 63%, p = 0.134, respectively). Combining both parameters resulted in an optimal sensitivity of 100% and intermediate specificity of 75%. The diagnostic accuracy was highest for the combined analysis than for the Alongituclinal MBF gradient or MFR alone (94% vs. 86%, p <= 0.003; and 94% vs. 70%, p <= 0.0002). CONCLUSIONS The combined evaluation of a Delta longitudinal MBF gradient and MFR may evolve as a new promising analytic approach to further optimize the identification of CAD lesions. (J Am Coll Cardiol Img 2014;7:387-96) (C) 2014 by the American College of Cardiology Foundation