[Impedance cardiography during exercise in the evaluation of left-ventricular function].

The measurement of mean pulmonary artery pressure is an important parameter for the assessment of left ventricular function. Transthoracic impedance cardiography is a method which, by measurement of transthoracic impedance, gives information on hemodynamic events, parameters of contractility, and valvular heart disease. In 50 patients mean pulmonary artery pressure was measured at rest and during exercise and compared to the corresponding changes in the impedance cardiogram. It was examined whether by means of impedance cardiography an elevated pulmonary artery pressure could be predicted. Group I consisted of 25 patients with normal pulmonary artery pressure at rest and during exercise, group II of 25 patient with pathologic pressure elevation. While the behavior of stroke volume, cardiac output, left ventricular ejection time, and Heather Index as measured by impedance cardiography did not allow a prediction of elevated pulmonary artery pressure, the impedance ratio O/dz/dtmin (IQ) was significantly greater in group II than in group I. In the patients tested elevated and normal pulmonary artery pressure during exercise could be predicted with an accuracy of 84%. The mean value of dz/dtmin at a work load of 100 watt was slightly but significantly higher in group I than in group II. The results show that the impedance ratio (IQ) can be used to assess left ventricular function non-invasively.