• Hyun Kim, Sung Oh Hwang, Christopher C Lee, Kang Hyun Lee, Jang Young Kim, Byung Su Yoo, Seung Hwan Lee, Jung Han Yoon, Kyung Hoon Choe, and Adam J Singer.
• Department of Emergency Medicine, Institute of Lifelong Health, Wonju College of Medicine, Yonsei University, Wonju, South Korea.
• Am. Heart J. 2008 Dec 1;156(6):1222.e1-7.

BackgroundCommon 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.MethodsTen 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.ResultsOn 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.ConclusionsRetrograde 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.

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