[Mechano- and impedance cardiography parameters in patients with heart failure in administration of a calcium antagonist. The significance of the Heather index].

By means of impedance- and mechanocardiography the effect of the calcium-channel blocker nisoldipine on the circadian course of hemodynamic parameters was measured in a placebo-controlled randomized double-blind study in 18 patients with heart failure (NYHA II). A significant effect of nisoldipine on left ventricular function was observed after 2 h but not any more 6 h following the administration of the drug. This effect was expressed by a reduction of the pre-ejection period (PEPc) and PEP/LVET in the systolic time intervals (STI) and a rise in stroke volume (delta V) and cardiac output (CO), as well as an increase of the Heather-index in impedance cardiography (ICG). In ICG the Heather-index proved to be a more reliable parameter of left ventricular function than the calculation of stroke volume and cardiac output, respectively. This is probably due to the fact that the distance between the electrode (L) is not considered for the Heather-index, while it has to be taken into account for determining stroke volume and cardiac output. When performing impedance cardiography in the elderly, the distance between the electrodes may be a source of error because of a lack of cooperation, possible underlying corpulance, or due to a restricted motility of the chest or the vertebral column. In these patients the Heather-index should be preferred to the calculation of stroke volume and cardiac output, whereas in healthy subjects the latter parameters seem to be of sufficient validity.