title: Breathing Maneuvers as a Vasoactive Stimulus for Detecting Inducible Myocardial Ischemia - An Experimental Cardiovascular Magnetic Resonance Study.
abstract: BACKGROUND
  Breathing maneuvers can elicit a similar vascular response as vasodilatory agents like adenosine; yet, their potential diagnostic utility in the presence of coronary artery stenosis is unknown. The objective of the study is to investigate if breathing maneuvers can non-invasively detect inducible ischemia in an experimental animal model when the myocardium is imaged with oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR).
  
  
  RESULTS
  In 11 anesthetised swine with experimentally induced significant stenosis (fractional flow reserve <0.75) of the left anterior descending coronary artery (LAD) and 9 control animals, OS-CMR at 3T was performed during two different breathing maneuvers, a long breath-hold; and a combined maneuver of 60s of hyperventilation followed by a long breath-hold. The resulting change of myocardial oxygenation was compared to the invasive measurements of coronary blood flow, blood gases, and oxygen extraction. In control animals, all breathing maneuvers could significantly alter coronary blood flow as hyperventilation decreased coronary blood flow by 34±23%. A long breath-hold alone led to an increase of 97±88%, while the increase was 346±327% (p<0.001), when the long breath-hold was performed after hyperventilation. In stenosis animals, the coronary blood flow response was attenuated after both hyperventilation and the following breath-hold. This was matched by the observed oxygenation response as breath-holds following hyperventilation consistently yielded a significant difference in the signal of the MRI images between the perfusion territory of the stenosis LAD and remote myocardium. There was no difference between the coronary territories during the other breathing maneuvers or in the control group at any point.
  
  
  CONCLUSIONS
  In an experimental animal model, the response to a combined breathing maneuver of hyperventilation with subsequent breath-holding is blunted in myocardium subject to significant coronary artery stenosis. This maneuver may allow for detecting severe coronary artery stenosis and have a significant clinical potential as a non-pharmacological method for diagnostic testing in patients with suspected coronary artery disease.
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada.|University Hospital Bern, Department Anaesthesiology and Pain Therapy, Inselspital, University of Bern, Bern, Switzerland.|University Hospital Bern, Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Kady
authors.initials: K
authors.lastname: Fischer
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada.|University Hospital Bern, Department Anaesthesiology and Pain Therapy, Inselspital, University of Bern, Bern, Switzerland.|University Hospital Bern, Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Dominik P
authors.initials: DP
authors.lastname: Guensch
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada.
authors.forename: Nancy
authors.initials: N
authors.lastname: Shie
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada.|Research Institute of the McGill University Health Centre, Montreal, QC, Canada.
authors.forename: Julie
authors.initials: J
authors.lastname: Lebel
authors.affiliation: Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada.|Department of Radiology, Université de Montréal, Montreal, QC, Canada.|Departments of Medicine and Diagnostic Radiology, McGill University, Montreal, QC, Canada.|Department of Cardiology, Heidelberg University Hospital, Heidelberg, Germany.|Departments of Cardiac Sciences and Radiology, University of Calgary, Calgary, Canada.
authors.forename: Matthias G
authors.initials: MG
authors.lastname: Friedrich
mesh_terms: D000241:Adenosine / Q000008:administration & dosage*; D000818:Animals; D001784:Blood Gas Analysis; D001945:Breathing Exercises / Q000379:methods; D017023:Coronary Angiography; D023921:Coronary Stenosis / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000503:physiopathology; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000502:physiology; D004195:Disease Models, Animal; D005471:Fluoroscopy; D006985:Hyperventilation / Q000503:physiopathology; D019028:Magnetic Resonance Imaging, Cine; D009206:Myocardium / Q000378:metabolism; D010100:Oxygen / Q000097:blood / Q000378:metabolism; D010101:Oxygen Consumption; D013552:Swine; D014665:Vasodilator Agents / Q000008:administration & dosage*
chemical_list: D014665:Vasodilator Agents; D000241:Adenosine; D010100:Oxygen