DOES IMPEDANCE CARDIOGRAPHY RELIABLY ESTIMATE LEFT-VENTRICULAR EJECTION FRACTION

Objective. The objective of our study was to evaluate impedance cardio graphy (IMP) as a noninvasive method to determine the left ventricular ejection fraction (LVEF). Methods. A total of 24 patients, 8 men and 16 women, aged 45.0 +/- 12.9 years, participated in the study. They us ed cardiotoxic chemotherapeutic drugs or suffered from cardiac failure . LVEF was measured by means of IMP (LVEFimp) and radionuclide ventric ulography (LVEFnuc). LVEFimp was calculated in three ways. Capan and c olleagues [13] proposed a formula in which LVEF (LVEFCap) can be calcu lated from the systolic time intervals, namely, left ventricular eject ion time and preejection time. Judy and colleagues [14] described a sy stolic (S) and a diastolic (D) part in the first derivative curve of t he impedance signal. The ratio SID might equal the LVEF (LVEFJud). A n ew LVEF calculation was introduced (LVEFimp) in this study based on th e first derivative of the impedance signal, the thoracic impedance, an d heart rate. Results. Mean LVEF was 59.9 +/- 8.4%, which did not diff er from LVEFnuc (59.9 +/- 7.1%). However the correlation between both methods was not significant (r = 0.29). Mean iud Was 63.9 +/- 17.4%, w hich was not significantly different from LVEFnuc, with a fair correla tion (r = 0.55). Mean LVEFimp was 59.2 +/- 9.4%, with a better correla tion with radionuclide ventriculography (r = 0.75). Conclusions. The r esults of this study indicate that the equations that have been used u ntil now can be improved. The new equation provides reliable LVEF valu es in this group of patients.