Impact of anatomical and functional severity of coronary atherosclerotic plaques on the transmural perfusion gradient: a [15O]H2O PET study.
BACKGROUND
Myocardial ischaemia occurs principally in the subendocardial layer, whereas conventional myocardial perfusion imaging provides no information on the transmural myocardial blood flow (MBF) distribution. Subendocardial perfusion measurements and quantification of the transmural perfusion gradient (TPG) could be more sensitive and specific for the detection of coronary artery disease (CAD). The current study aimed to determine the impact of lesion severity as assessed by the fractional flow reserve (FFR) on subendocardial perfusion and the TPG using [(15)O]H2O positron emission tomography (PET) imaging in patients evaluated for CAD.


RESULTS
Sixty-six patients with anginal chest pain were prospectively enrolled and underwent [(15)O]H2O myocardial perfusion PET imaging. Subsequently, invasive coronary angiography was performed and FFR obtained in all coronary arteries irrespective of the PET imaging results. Thirty (45%) patients were diagnosed with significant CAD (i.e. FFR ≤0.80), whereas on a per vessel analysis (n = 198), 53 (27%) displayed a positive FFR. Transmural hyperaemic MBF decreased significantly from 3.09 ± 1.16 to 1.67 ± 0.57 mL min(-1) g(-1) (P < 0.001) in non-ischaemic and ischaemic myocardium, respectively. The TPG decreased during hyperaemia when compared with baseline (1.20 ± 0.14 vs. 0.94 ± 0.17, P < 0.001), and was lower in arteries with a positive FFR (0.97 ± 0.16 vs. 0.88 ± 0.18, P < 0.01). A TPG threshold of 0.94 yielded an accuracy to detect CAD of 59%, which was inferior to transmural MBF with an optimal cutoff of 2.20 mL min(-1) g(-1) and an accuracy of 85% (P < 0.001). Diagnostic accuracy of subendocardial perfusion measurements was comparable with transmural MBF (83 vs. 85%, respectively, P = NS).


CONCLUSIONS
Cardiac [(15)O]H2O PET imaging is able to distinguish subendocardial from subepicardial perfusion in the myocardium of normal dimensions. Hyperaemic TPG is significantly lower in ischaemic myocardium. This technique can potentially be employed to study subendocardial perfusion impairment in more detail. However, the diagnostic accuracy of subendocardial hyperaemic perfusion and TPG appears to be limited compared with quantitative transmural MBF, warranting further study.
Department of Cardiology, VU University Medical Center, Amsterdam, De Boelelaan 1117, 1081 HV, The Netherlands.
Ibrahim
I
Danad
Department of Nuclear Medicine & PET Research and Radiology, VU University Medical Center, Amsterdam, The Netherlands.
Pieter G
PG
Raijmakers
Department of Nuclear Medicine & PET Research and Radiology, VU University Medical Center, Amsterdam, The Netherlands.
Hendrik J
HJ
Harms
Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands.
Martijn W
MW
Heymans
Department of Cardiology, VU University Medical Center, Amsterdam, De Boelelaan 1117, 1081 HV, The Netherlands.
Niels
N
van Royen
Uppsala University PET Center, Uppsala University Hospital, Uppsala, Sweden.
Mark
M
Lubberink
Department of Nuclear Medicine & PET Research and Radiology, VU University Medical Center, Amsterdam, The Netherlands.
Ronald
R
Boellaard
Department of Cardiology, VU University Medical Center, Amsterdam, De Boelelaan 1117, 1081 HV, The Netherlands.
Albert C
AC
van Rossum
Department of Nuclear Medicine & PET Research and Radiology, VU University Medical Center, Amsterdam, The Netherlands.
Adriaan A
AA
Lammertsma
Department of Cardiology, VU University Medical Center, Amsterdam, De Boelelaan 1117, 1081 HV, The Netherlands p.knaapen@vumc.nl.
Paul
P
Knaapen
D000787:Angina Pectoris / Q000503:physiopathology; D003324:Coronary Artery Disease / Q000503:physiopathology*; D003326:Coronary Circulation / Q000502:physiology; D023921:Coronary Stenosis / Q000503:physiopathology*; D005260:Female; D053805:Fractional Flow Reserve, Myocardial / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods; D010104:Oxygen Radioisotopes; D058226:Plaque, Atherosclerotic / Q000503:physiopathology*; D049268:Positron-Emission Tomography / Q000379:methods; D011446:Prospective Studies; D019275:Radiopharmaceuticals
D010104:Oxygen Radioisotopes; D019275:Radiopharmaceuticals
Coronary artery disease; Fractional flow reserve; Myocardial perfusion; Positron emission tomography; Transmural perfusion gradient