title: Relationship of vasodilator-induced changes in myocardial oxygenation with the severity of coronary artery stenosis: a study using oxygenation-sensitive cardiovascular magnetic resonance.
abstract: OBJECTIVE
  To explore the impact of the functional severity of coronary artery stenosis on changes in myocardial oxygenation during pharmacological vasodilation, using oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR) imaging and invasive fractional flow reserve (FFR). An FFR is considered a standard of reference for assessing haemodynamic relevance of coronary artery stenosis; yet, the relationship of FFR to changes in myocardial oxygenation during vasodilator stress and thus to an objective marker for ischaemia on the tissue level is not well understood.
  
  
  RESULTS
  We prospectively recruited 64 patients with suspected/known coronary artery disease undergoing invasive angiography. The FFR was performed in intermediate coronary artery stenosis. OS-CMR images were acquired using a T2*-sensitive sequence before and after adenosine-induced vasodilation, with myocardial segments matched to angiography. Very strict image quality criteria were defined to ensure the validity of results. The FFR was performed in 37 patients. Because of the strict image quality criteria, 41% of segments had to be excluded, leaving 29/64 patients for the blinded OS-CMR analysis. Coronary territories with an associated FFR of <0.80 showed a lack of increase in myocardial oxygenation [mean signal intensity (ΔSI) -0.49%; 95% confidence interval (CI) -3.78 to 2.78 vs. +7.30%; 95% CI 4.08 to 10.64; P < 0.001]. An FFR of <0.54 best predicted a complete lack of a vasodilator-induced oxygenation increase (sensitivity 71% and specificity 75%). An OS-CMR ΔSI <4.78% identified an FFR of <0.8 with a sensitivity of 86% and specificity of 92%.
  
  
  CONCLUSIONS
  An FFR of <0.80 is associated with a lack of an adenosine-inducible increase in oxygenation of the dependent coronary territory, while a complete lack of such an increase was best predicted by an FFR of <0.54. Further studies are warranted to identify clinically meaningful cut-off values for FFR measurements and to assess the utility of OS-CMR as an alternative clinical tool for assessing the functional relevance of coronary artery stenosis.
authors.affiliation: Stephenson CMR Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Judy M
authors.initials: JM
authors.lastname: Luu
authors.affiliation: Stephenson CMR Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada Philippa and Marvin Carsley Cardiovascular MR Centre at the Montreal Heart Institute, Université de Montréal, 5000 Rue Belanger, Montreal, QC, Canada H1T 1C8 mgwfriedrich@gmail.com.
authors.forename: Matthias G
authors.initials: MG
authors.lastname: Friedrich
authors.affiliation: Stephenson CMR Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada Heart Care Partners, Brisbane, Australia.
authors.forename: Jodi
authors.initials: J
authors.lastname: Harker
authors.affiliation: Royal Hobart Hospital, Hobart, TAS, Australia.
authors.forename: Nathan
authors.initials: N
authors.lastname: Dwyer
authors.affiliation: Stephenson CMR Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada Department of Anaesthesiology and Pain Medicine, Bern University Hospital, Bern, Switzerland.
authors.forename: Dominik
authors.initials: D
authors.lastname: Guensch
authors.affiliation: Stephenson CMR Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mikami
authors.affiliation: Alberta Bone and Joint Health Institute, University of Calgary, Calgary, AB, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Faris
authors.affiliation: Stephenson CMR Centre at the Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada Alfred Hospital & Baker IDI Research Institute, Melbourne, VIC, Australia.
authors.forename: James L
authors.initials: JL
authors.lastname: Hare
mesh_terms: D000241:Adenosine; D000368:Aged; D023921:Coronary Stenosis / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014665:Vasodilator Agents
chemical_list: D014665:Vasodilator Agents; D000241:Adenosine
keywords: Cardiovascular magnetic resonance; Coronary artery disease; Fractional flow reserve; Ischaemia; Oxygenation-sensitive imaging