title: Perfusion MRI at rest in subacute and chronic myocardial infarct.
abstract: BACKGROUND
  Perfusion magnetic resonance imaging (MRI) and delayed contrast-enhanced MRI (DE-MRI) serve as tools for tissue characterization.
  
  
  OBJECTIVE
  To assess and compare semi-quantitative parameters of myocardial infarct (MI) in the subacute and chronic phase, and to correlate these parameters with qualitative enhancement analysis.
  
  
  METHODS
  Perfusion MRI at rest and DE-MRI were performed in 63 patients with anterior wall MI at 2-3 weeks after revascularization and repeated after 6 months. Descriptive enhancement parameters of contrast arrival time, initial upslope, enhancement at normal tissue peak (TTPn) and wash-out slope, and kinetic tissue parameters rBF, K (trans), k ep and v e were calculated. Subacute infarct tissue was compared to normal myocardium and chronic infarct tissue. Patients were stratified at baseline according to a qualitative grading of hypoenhancement based on first-pass enhancement and presence of microvascular obstruction (MO) at perfusion MRI and on persistent MO at DE-MRI. The qualitative grade was correlated to semi-quantitative perfusion MRI parameters.
  
  
  RESULTS
  Initial upslope, enhancement at TTPn, rBF, and k ep were decreased and wash-out slope and v e were increased in infarct tissue (P < 0.001 for all analyses). Infarct tissue v e decreased from baseline to 6 months (P = 0.045). At baseline infarct tissue with persistent MO revealed decreased K (trans) and delayed contrast arrival, and more pronounced decrease of enhancement at TTPn, rBF and k ep compared to other enhancement groups (P < 0.008 for pairwise analyses).
  
  
  CONCLUSIONS
  Perfusion is decreased in subacute reperfused infarct tissue compared to normal tissue. K (trans) is not decreased, consistent with increased surface area of the vascular bed of the subacute infarct. Infarct tissue v e is increased, and decreases with scarring. The presence of persistent MO correlates to more pronounced perfusion reduction and results in delayed contrast arrival, indicating microvascular collateral circulation.
authors: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Rikshospitalet Faculty of Medicine, University of Oslo, Oslo einar.hopp@oslo-universitetssykehus.no.
authors: Einar
authors: E
authors: Hopp
authors: The Intervention Centre, Oslo University Hospital, Rikshospitalet Department of Physics, University of Oslo.
authors: Atle
authors: A
authors: Bjørnerud
authors: Department of Cardiology, Oslo University Hospital, Rikshospitalet.
authors: Ketil
authors: K
authors: Lunde
authors: Department of Cardiology, Oslo University Hospital, Ullevål, Norway.
authors: Svein
authors: S
authors: Solheim
authors: Department of Cardiology, Oslo University Hospital, Rikshospitalet.
authors: Svend
authors: S
authors: Aakhus
authors: Faculty of Medicine, University of Oslo, Oslo Department of Cardiology, Oslo University Hospital, Ullevål, Norway.
authors: Harald
authors: H
authors: Arnesen
authors: Department of Cardiology, Oslo University Hospital, Rikshospitalet.
authors: Kolbjørn
authors: K
authors: Forfang
authors: Faculty of Medicine, University of Oslo, Oslo Department of Cardiology, Oslo University Hospital, Rikshospitalet.
authors: Thor
authors: T
authors: Edvardsen
authors: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Rikshospitalet Faculty of Medicine, University of Oslo, Oslo.
authors: Hans-Jørgen
authors: HJ
authors: Smith
mesh_terms: D002908:Chronic Disease; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000473:pathology* / Q000601:surgery; D062645:Percutaneous Coronary Intervention; D015607:Stents
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA
keywords: Cardiac; MR imaging; MR perfusion; infarction