title: Considerations when measuring myocardial perfusion reserve by cardiovascular magnetic resonance using regadenoson.
abstract: BACKGROUND
  Adenosine cardiovascular magnetic resonance (CMR) can accurately quantify myocardial perfusion reserve. While regadenoson is increasingly employed due to ease of use, imaging protocols have not been standardized. We sought to determine the optimal regadenoson CMR protocol for quantifying myocardial perfusion reserve index (MPRi) - more specifically, whether regadenoson stress imaging should be performed before or after rest imaging.
  
  
  METHODS
  Twenty healthy subjects underwent CMR perfusion imaging during resting conditions, during regadenoson-induced hyperemia (0.4 mg), and after 15 min of recovery. In 10/20 subjects, recovery was facilitated with aminophylline (125 mg). Myocardial time-intensity curves were used to obtain left ventricular cavity-normalized myocardial up-slopes. MPRi was calculated in two different ways: as the up-slope ratio of stress to rest (MPRi-rest), and the up-slope ratio of stress to recovery (MPRi-recov).
  
  
  RESULTS
  In all 20 subjects, MPRi-rest was 1.78 ± 0.60. Recovery up-slope did not return to resting levels, regardless of aminophylline use. Among patients not receiving aminophylline, MPRi-recov was 36 ± 16% lower than MPRi-rest (1.13 ± 0.38 vs. 1.82 ± 0.73, P = 0.001). In the 10 patients whose recovery was facilitated with aminophylline, MPRi-recov was 20 ± 24% lower than MPRi-rest (1.40 ± 0.35 vs. 1.73 ± 0.43, P = 0.04), indicating incomplete reversal. In 3 subjects not receiving aminophylline and 4 subjects receiving aminophylline, up-slope at recovery was greater than at stress, suggesting delayed maximal hyperemia.
  
  
  CONCLUSIONS
  MPRi measurements from regadenoson CMR are underestimated if recovery perfusion is used as a substitute for resting perfusion, even when recovery is facilitated with aminophylline. True resting images should be used to allow accurate MPRi quantification. The delayed maximal hyperemia observed in some subjects deserves further study.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT00871260.
authors.affiliation: Departments of Medicine and Radiology, University of Chicago, Cardiac Imaging Center, Chicago, IL 60637, USA.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Bhave
authors.forename: Benjamin H
authors.initials: BH
authors.lastname: Freed
authors.forename: Chattanong
authors.initials: C
authors.lastname: Yodwut
authors.forename: Denise
authors.initials: D
authors.lastname: Kolanczyk
authors.forename: Karin
authors.initials: K
authors.lastname: Dill
authors.forename: Roberto M
authors.initials: RM
authors.lastname: Lang
authors.forename: Victor
authors.initials: V
authors.lastname: Mor-Avi
authors.forename: Amit R
authors.initials: AR
authors.lastname: Patel
mesh_terms: D000328:Adult; D000628:Aminophylline / Q000008:administration & dosage; D001794:Blood Pressure; D002641:Chicago; D003287:Contrast Media; D003326:Coronary Circulation / Q000187:drug effects; D005260:Female; D006339:Heart Rate; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D058915:Purinergic P1 Receptor Antagonists / Q000008:administration & dosage; D011687:Purines; D011720:Pyrazoles; D020127:Recovery of Function; D012016:Reference Values; D015203:Reproducibility of Results; D013318:Stroke Volume; D013997:Time Factors; D014665:Vasodilator Agents; D016277:Ventricular Function, Left; D055815:Young Adult
chemical_list: D003287:Contrast Media; D058915:Purinergic P1 Receptor Antagonists; D011687:Purines; D011720:Pyrazoles; D014665:Vasodilator Agents; D000628:Aminophylline; C430916:regadenoson