PET-measured longitudinal flow gradient correlates with invasive fractional flow reserve in CAD patients.
OBJECTIVE
We aimed to evaluate whether a PET-determined longitudinal decrease in myocardial blood flow (MBF) or gradient, assumed as a more specific flow parameter for epicardial resistance, correlates with invasively measured fractional flow reserve (FFR) in coronary artery disease (CAD) patients.


RESULTS
In 29 patients with suspected or known CAD, myocardial perfusion and MBF in mL/g/min was determined with 13N-ammonia PET/CT during regadenoson stimulation and at rest, and corresponding myocardial flow reserve (MFR = MBF stress/MBF rest) was calculated. MBF parameters were assessed in the myocardial region with stress-related perfusion defect and with stenosis ≥50% (Region 1), without defect but with stenosis ≥50% (Region 2), or without stenosis ≥50% (Region 3). Hyperaemic MBFs were significantly lower in the mid-distal than in the mid-left ventricular myocardium in Regions 1-3 [median and IQ range: 1.57 (1.24, 1.84) vs. 1.87 (1.61, 2.00), and 1.23 (1.11, 1.86) vs. 1.89 (1.80, 1.97), and 1.78 (1.48, 2.00) vs. 1.94 (1.84, 2.05) mL/g/min, P < 0.0001]. Resulting longitudinal MBF gradient during hyperaemic flows was more pronounced in Region 2 than in Regions 1 and 3, respectively [-0.46 (-0.70, -0.10) vs. -0.17 (-0.29, -0.11) and -0.15 (-0.25, -0.09) mL/g/min, respectively, P < 0.01]. There was a significant correlation between the hyperaemic longitudinal MBF gradient and FFR (r = 0.95; P < 0.0001), while this association was less pronounced for corresponding MFR (r = 0.50; P = 0.006).


CONCLUSIONS
The observed close correlation between a longitudinal MBF gradient during hyperaemic flows and invasively measured FFR suggests the longitudinal flow gradient as an emerging non-invasive index of flow-limiting CAD.
Division of Nuclear Medicine - Cardiovascular Section, Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, JHOC 3225, 601 N. Caroline Street, Baltimore, MD 21287, USA.
Ines
I
Valenta
Division of Nuclear Medicine - Cardiovascular Section, Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, JHOC 3225, 601 N. Caroline Street, Baltimore, MD 21287, USA.
Alexander
A
Antoniou
Division of Nuclear Medicine - Cardiovascular Section, Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, JHOC 3225, 601 N. Caroline Street, Baltimore, MD 21287, USA.
Wael
W
Marashdeh
Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD, USA.
Thorsten
T
Leucker
Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD, USA.
Edward
E
Kasper
Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD, USA.
Steven R
SR
Jones
Division of Nuclear Medicine - Cardiovascular Section, Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, JHOC 3225, 601 N. Caroline Street, Baltimore, MD 21287, USA.
Robert F
RF
Dannals
Division of Nuclear Medicine - Cardiovascular Section, Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, JHOC 3225, 601 N. Caroline Street, Baltimore, MD 21287, USA.
Lilja
L
Solnes
Division of Nuclear Medicine - Cardiovascular Section, Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, JHOC 3225, 601 N. Caroline Street, Baltimore, MD 21287, USA.
Martin G
MG
Pomper
Division of Nuclear Medicine - Cardiovascular Section, Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, JHOC 3225, 601 N. Caroline Street, Baltimore, MD 21287, USA.|Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD, USA.
Thomas H
TH
Schindler
D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology; D015331:Cohort Studies; D017023:Coronary Angiography / Q000379:methods; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003326:Coronary Circulation / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D053805:Fractional Flow Reserve, Myocardial / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D018709:Statistics, Nonparametric
CAD; PET; circulation; coronary stenosis; flow gradient; microvascular function; myocardial blood flow; myocardial flow reserve; myocardial perfusion