title: Myocardial perfusion imaging after coronary artery bypass surgery using cardiovascular magnetic resonance: a validation study.
abstract: BACKGROUND
  Absolute quantification of perfusion with cardiovascular magnetic resonance has not previously been applied in patients with coronary artery bypass grafting (CABG). Owing to increased contrast bolus dispersion due to the greater distance of travel through a bypass graft, this approach may result in systematic underestimation of myocardial blood flow (MBF). As resting MBF remains normal in segments supplied by noncritical coronary stenosis (<85%), measurement of perfusion in such territories may be utilized to reveal systematic error in the quantification of MBF. The objective of this study was to test whether absolute quantification of perfusion with cardiovascular magnetic resonance systematically underestimates MBF in segments subtended by bypass grafts.
  
  
  RESULTS
  The study population comprised 28 patients undergoing elective CABG for treatment of multivessel coronary artery disease. Eligible patients had angiographic evidence of at least 1 myocardial segment subtended by a noncritically stenosed coronary artery (<85%). Subjects were studied at 1.5 T, with evaluation of resting MBF using model-independent deconvolution. Analyses were confined to myocardial segments subtended by native coronary arteries with <85% stenosis at baseline, and MBF was compared in grafted and ungrafted segments before and after revascularization. A total of 249 segments were subtended by coronary arteries with <85% stenosis at baseline. After revascularization, there was no significant difference in MBF in ungrafted (0.82±0.19 mL/min/g) versus grafted segments (0.82±0.15 mL/min/g, P=0.57). In the latter, MBF after revascularization did not change significantly from baseline (0.86±0.20 mL/min/g, P=0.82).
  
  
  CONCLUSIONS
  Model-independent deconvolution analysis does not systematically underestimate blood flow in graft-subtended territories, justifying the use of this methodology to evaluate myocardial perfusion in patients with CABG.
authors.affiliation: University of Oxford Centre for Clinical Magnetic Resonance Research, John Radcliffe Hospital, Oxford, United Kingdom.
authors.forename: J Ranjit
authors.initials: JR
authors.lastname: Arnold
authors.forename: Jane M
authors.initials: JM
authors.lastname: Francis
authors.forename: Theodoros D
authors.initials: TD
authors.lastname: Karamitsos
authors.forename: Chris C
authors.initials: CC
authors.lastname: Lim
authors.forename: William J
authors.initials: WJ
authors.lastname: van Gaal
authors.forename: Luca
authors.initials: L
authors.lastname: Testa
authors.forename: Paul
authors.initials: P
authors.lastname: Bhamra-Ariza
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Selvanayagam
authors.forename: Rana
authors.initials: R
authors.lastname: Sayeed
authors.forename: Stephen
authors.initials: S
authors.lastname: Westaby
authors.forename: Adrian P
authors.initials: AP
authors.lastname: Banning
authors.forename: Stefan
authors.initials: S
authors.lastname: Neubauer
authors.forename: Michael
authors.initials: M
authors.lastname: Jerosch-Herold
mesh_terms: D003287:Contrast Media; D017023:Coronary Angiography; D001026:Coronary Artery Bypass; D003324:Coronary Artery Disease / Q000503:physiopathology / Q000601:surgery*; D003326:Coronary Circulation; D023921:Coronary Stenosis / Q000175:diagnosis; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging; D055414:Myocardial Perfusion Imaging
chemical_list: D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA