Left ventricular ejection and the Heather Index measured by non-invasive methods during postural changes in man.

Differences have been found, which are usually 1% or less, between the left ventricular ejection time measured from the external carotid pulse tracing, and from the rate of change of thoracic impedance (dZ/dt) waveform, using either the second heart sound or the X-point of the dZ/dt tracing as the end-point. The Heather Index obtained from the ECG and dZ/dt tracings has been correlated with other indices of cardiac performance. The changes observed in the physiological variables during head-up and head-down tilting were in the expected directions.