title: Direction of blood flow from the left ventricle during cardiopulmonary resuscitation in humans: its implications for mechanism of blood flow.
abstract: BACKGROUND
  Common mechanisms proposed to explain forward blood flow during cardiopulmonary resuscitation (CPR) include the cardiac and thoracic pumps. However, the exact role of the left ventricle in promoting forward blood flow during standard CPR in humans is mostly unknown. The aim of this study was to explore the role of the left ventricle in generating forward blood flow during standard CPR in humans by observing the direction of blood flow during CPR.
  
  
  METHODS
  Ten patients with non-traumatic cardiac arrest were enrolled in this study. During CPR, contrast echocardiography with agitated saline was performed in the left ventricle and the aorta, and the direction of contrast flow was assessed using transesophageal echocardiography.
  
  
  RESULTS
  On injecting the contrast in the aortic root, anterograde flow from the aorta during the compression phase was observed. No aortic regurgitation was present. Retrograde blood flow from the left ventricle into the left atrium as well as anterograde blood flow from the left ventricle into the aorta during the compression phase of CPR was observed in all cases. On injecting the contrast in the aortic root, anterograde flow from the aorta during the compression phase was observed. During each cycle of chest compression, the mitral valve closed during compression and opened during relaxation, and the aortic valve opened during compression and closed during relaxation.
  
  
  CONCLUSIONS
  Retrograde flow to the left atrium and forward blood flow onto the aorta on left ventricular contrast echocardiography during the compression phase suggests that extrinsic compression of the left ventricle by external chest compression acts as a pump in generating blood flow during standard CPR in humans.
authors.affiliation: Department of Emergency Medicine, Institute of Lifelong Health, Wonju College of Medicine, Yonsei University, Wonju, South Korea.
authors.forename: Hyun
authors.initials: H
authors.lastname: Kim
authors.forename: Sung Oh
authors.initials: SO
authors.lastname: Hwang
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Lee
authors.forename: Kang Hyun
authors.initials: KH
authors.lastname: Lee
authors.forename: Jang Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Byung Su
authors.initials: BS
authors.lastname: Yoo
authors.forename: Seung Hwan
authors.initials: SH
authors.lastname: Lee
authors.forename: Jung Han
authors.initials: JH
authors.lastname: Yoon
authors.forename: Kyung Hoon
authors.initials: KH
authors.lastname: Choe
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Singer
mesh_terms: D000328:Adult; D000368:Aged; D001021:Aortic Valve / Q000503:physiopathology; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D016887:Cardiopulmonary Resuscitation; D003287:Contrast Media; D003971:Diastole / Q000502:physiology; D004452:Echocardiography; D017548:Echocardiography, Transesophageal; D004562:Electrocardiography; D005260:Female; D006323:Heart Arrest / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000503:physiopathology; D009200:Myocardial Contraction / Q000502:physiology; D011446:Prospective Studies; D013318:Stroke Volume / Q000502:physiology; D013599:Systole / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D003287:Contrast Media; D002245:Carbon Dioxide