title: Assessment of myocardial reactivity to controlled hypercapnia with free-breathing T2-prepared cardiac blood oxygen level-dependent MR imaging.
abstract: OBJECTIVE
  To examine whether controlled and tolerable levels of hypercapnia may be an alternative to adenosine, a routinely used coronary vasodilator, in healthy human subjects and animals.
  
  
  METHODS
  Human studies were approved by the institutional review board and were HIPAA compliant. Eighteen subjects had end-tidal partial pressure of carbon dioxide (PetCO2) increased by 10 mm Hg, and myocardial perfusion was monitored with myocardial blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging. Animal studies were approved by the institutional animal care and use committee. Anesthetized canines with (n = 7) and without (n = 7) induced stenosis of the left anterior descending artery (LAD) underwent vasodilator challenges with hypercapnia and adenosine. LAD coronary blood flow velocity and free-breathing myocardial BOLD MR responses were measured at each intervention. Appropriate statistical tests were performed to evaluate measured quantitative changes in all parameters of interest in response to changes in partial pressure of carbon dioxide.
  
  
  RESULTS
  Changes in myocardial BOLD MR signal were equivalent to reported changes with adenosine (11.2% ± 10.6 [hypercapnia, 10 mm Hg] vs 12% ± 12.3 [adenosine]; P = .75). In intact canines, there was a sigmoidal relationship between BOLD MR response and PetCO2 with most of the response occurring over a 10 mm Hg span. BOLD MR (17% ± 14 [hypercapnia] vs 14% ± 24 [adenosine]; P = .80) and coronary blood flow velocity (21% ± 16 [hypercapnia] vs 26% ± 27 [adenosine]; P > .99) responses were similar to that of adenosine infusion. BOLD MR signal changes in canines with LAD stenosis during hypercapnia and adenosine infusion were not different (1% ± 4 [hypercapnia] vs 6% ± 4 [adenosine]; P = .12).
  
  
  CONCLUSIONS
  Free-breathing T2-prepared myocardial BOLD MR imaging showed that hypercapnia of 10 mm Hg may provide a cardiac hyperemic stimulus similar to adenosine.
authors.affiliation: From the Biomedical Imaging Research Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, 8700 Beverly Blvd, PACT Building, Suite 800, Los Angeles, CA 90048 (H.J.Y., R.T., I.C., A.K., B.S., D.L., R.D.); Departments of Bioengineering (H.J.Y., A.K., D.L.), Anesthesiology (R.Y.), and Medicine (D.L., R.D.), University of California, Los Angeles, Calif; Department of Physiology (O.S., M.K., J.A.F.) and Department of Anesthesiology, University Health Network (J.A.F.), University of Toronto, Toronto, Ontario, Canada; IMT Institute for Advanced Studies Lucca, Lucca, Italy (S.A.T.); Siemens Medical Solutions USA, Chicago, Ill (X.B.); and Department of Anesthesiology (R.Y., J.T., A.H.C.) and Cedars-Sinai Heart Institute (R.D.), Cedars-Sinai Medical Center, Los Angeles, Calif.
authors.forename: Hsin-Jung
authors.initials: HJ
authors.lastname: Yang
authors.forename: Roya
authors.initials: R
authors.lastname: Yumul
authors.forename: Richard
authors.initials: R
authors.lastname: Tang
authors.forename: Ivan
authors.initials: I
authors.lastname: Cokic
authors.forename: Michael
authors.initials: M
authors.lastname: Klein
authors.forename: Avinash
authors.initials: A
authors.lastname: Kali
authors.forename: Olivia
authors.initials: O
authors.lastname: Sobczyk
authors.forename: Behzad
authors.initials: B
authors.lastname: Sharif
authors.forename: Jun
authors.initials: J
authors.lastname: Tang
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Bi
authors.forename: Sotirios A
authors.initials: SA
authors.lastname: Tsaftaris
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
authors.forename: Antonio Hernandez
authors.initials: AH
authors.lastname: Conte
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Fisher
authors.forename: Rohan
authors.initials: R
authors.lastname: Dharmakumar
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D003326:Coronary Circulation / Q000502:physiology*; D004285:Dogs; D004562:Electrocardiography; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010092:Oximetry; D015203:Reproducibility of Results; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014665:Vasodilator Agents; D000241:Adenosine
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