Echocardiographic study of the isovolumetric contraction time.

The isovolumetric contraction time of the human heart, i.e. the time interval from the completion of the mitral valve closure to the beginning of the aortic valve opening was measured by means of echocardiography. The result of this investigation verifies a theoretical prediction by the author, that the isovolumetric contraction time should decrease more than in proportion with the heart period when the heart rate increases due to exercise, and that it should even disappear at a sufficiently elevated heart rate.