title: Diagnostic value of PET-measured longitudinal flow gradient for the identification of coronary artery disease.
abstract: OBJECTIVE
  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 (13)N-ammonia and PET/CT in ml/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 Δlongitudinal 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 Δlongitudinal 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 Δlongitudinal MBF gradient or MFR alone (94% vs. 86%, p ≤ 0.003; and 94% vs. 70%, p ≤ 0.0002).
  
  
  CONCLUSIONS
  The combined evaluation of a Δlongitudinal MBF gradient and MFR may evolve as a new promising analytic approach to further optimize the identification of CAD lesions.
authors.affiliation: Division of Nuclear Medicine, Department of Radiology, and Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Ines
authors.initials: I
authors.lastname: Valenta
authors.affiliation: Department of Specialties in Medicine, University Hospitals of Geneva, Geneva, Switzerland.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Quercioli
authors.affiliation: Division of Nuclear Medicine, Department of Radiology, and Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, Maryland. Electronic address: Thomas.h.schindler@gmail.com.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Schindler
mesh_terms: D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D017023:Coronary Angiography / Q000379:methods; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D023921:Coronary Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D006940:Hyperemia / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D014665:Vasodilator Agents
chemical_list: D014665:Vasodilator Agents
keywords: CAD; MFR; PET; blood flow; circulation; coronary stenosis; flow gradient; microvascular function; myocardial perfusion