Evidence for the 'cardiac pump theory' in cardiopulmonary resuscitation in man by transesophageal echocardiography.

There are two theories to explain the mechanism of blood flow during cardiopulmonary resuscitation: The 'Cardiac Pump Theory' and the 'Thoracic Pump Theory'. We have performed transesophageal echocardiography during the resuscitation of a patient with cardiopulmonary arrest. By this method we could study the motion of the aortic, mitral and tricuspid valves and the changes in ventricular size during cardiopulmonary resuscitation in man. We demonstrated an opening of the aortic valve during thoracic compression with simultaneous closure of the mitral and tricuspid valves. During relaxation of the chest, a rapid opening of the atrioventricular valves and closure of the aortic valve was noted. Short interruption of cardiopulmonary resuscitation to test for spontaneous heart action lead to echocontrast in all four heart chambers through stasis of blood, which resolved on continuation of cardiopulmonary resuscitation. This 'washing out' phenomenon enables visualization of blood flow through the aortic valve during compression, and through the mitral valve during relaxation. These observations favour the Cardiac Pump Theory as the predominant hemodynamic principle of blood flow during cardiopulmonary resuscitation in man.