title: Feasibility and safety of high-dose adenosine perfusion cardiovascular magnetic resonance.
abstract: BACKGROUND
  Adenosine is the most widely used vasodilator stress agent for cardiovascular magnetic resonance (CMR) perfusion studies. With the standard dose of 140 mcg/kg/min some patients fail to demonstrate characteristic haemodynamic changes: a significant increase in heart rate (HR) and mild decrease in systolic blood pressure (SBP). Whether an increase in the rate of adenosine infusion would improve peripheral and, likely, coronary vasodilatation in those patients is unknown. The aim of the present study was to assess the tolerance and safety of a high-dose adenosine protocol in patients with inadequate haemodynamic response to the standard adenosine protocol when undergoing CMR perfusion imaging.
  
  
  METHODS
  98 consecutive patients with known or suspected coronary artery disease (CAD) underwent CMR perfusion imaging at 1.5 Tesla. Subjects were screened for contraindications to adenosine, and an electrocardiogram was performed prior to the scan. All patients initially received the standard adenosine protocol (140 mcg/kg/min for at least 3 minutes). If the haemodynamic response was inadequate (HR increase < 10 bpm or SBP decrease < 10 mmHg) then the infusion rate was increased up to a maximum of 210 mcg/kg/min (maximal infusion duration 7 minutes).
  
  
  RESULTS
  All patients successfully completed the CMR scan. Of a total of 98 patients, 18 (18%) did not demonstrate evidence of a significant increase in HR or decrease in SBP under the standard adenosine infusion rate. Following the increase in the rate of infusion, 16 out of those 18 patients showed an adequate haemodynamic response. One patient of the standard infusion group and two patients of the high-dose group developed transient advanced AV block. Significantly more patients complained of chest pain in the high-dose group (61% vs. 29%, p = 0.009). On multivariate analysis, age > 65 years and ejection fraction < 57% were the only independent predictors of blunted haemodynamic responsiveness to adenosine.
  
  
  CONCLUSIONS
  A substantial number of patients do not show adequate peripheral haemodynamic response to standard-dose adenosine stress during perfusion CMR imaging. Age and reduced ejection fraction are predictors of inadequate response to standard dose adenosine. A high-dose adenosine protocol (up to 210 mcg/kg/min) is well tolerated and results in adequate haemodynamic response in nearly all patients.
authors.affiliation: Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, UK. theo.karamitsos@cardiov.ox.ac.uk
authors.forename: Theodoros D
authors.initials: TD
authors.lastname: Karamitsos
authors.forename: Ntobeko A B
authors.initials: NA
authors.lastname: Ntusi
authors.forename: Jane M
authors.initials: JM
authors.lastname: Francis
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Holloway
authors.forename: Saul G
authors.initials: SG
authors.lastname: Myerson
authors.forename: Stefan
authors.initials: S
authors.lastname: Neubauer
mesh_terms: D000241:Adenosine / Q000008:administration & dosage / Q000009:adverse effects; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D054537:Atrioventricular Block / Q000139:chemically induced; D001794:Blood Pressure / Q000187:drug effects; D002637:Chest Pain / Q000139:chemically induced; D016009:Chi-Square Distribution; D003324:Coronary Artery Disease / Q000175:diagnosis* / Q000503:physiopathology; D003326:Coronary Circulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D004739:England; D005240:Feasibility Studies; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D007262:Infusions, Intravenous; D016015:Logistic Models; D008279:Magnetic Resonance Imaging / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000009:adverse effects / Q000379:methods*; D011237:Predictive Value of Tests; D018570:Risk Assessment; D012307:Risk Factors; D013318:Stroke Volume; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000009:adverse effects; D055815:Young Adult
chemical_list: D014665:Vasodilator Agents; D000241:Adenosine