Noninvasive measurement of cardiac output: Two methods compared in patients with mitral regurgitation

In search for the origin of the less reliable cardiac output (CO) estimatio ns by means of electrical impedance cardiography (EIC), the authors hypothe sized that cardiac valve pathology might be one of the reasons. Twenty-six patients were examined by means of echo Doppler (ED) and EIC. The cardiac v alve status was obtained by means of echocardiography and color Doppler flo w, while CO was obtained by means of both methods. Seventeen patients had n o valve pathology (nVP) while nine patients had mild to moderate mitral reg urgitation (MVR). The overall correlation between the calculation of CO by means of the two methods was good (r = 0.85, p < 0.001, mean difference and standard deviation: 0.20 +/- 0.74 L/min), while there was no significant d ifference between the paired values. After division into an nVP and an MVR population, the results showed an even closer agreement between the CO valu es in the nVP population (r = 0.88, p < 0.001, mean difference and standard deviation: 0.15 +/- 0.68 L/min). Furthermore, significant differences were found in the first derivative of the impedance (dZ/dt) signals of these gr oups. Although the agreement between ED and EIC was slightly lower in the M VR population, EIC reliably estimated CO, even in case of MVR. The impedanc e signal itself gave an indication for the existence of MVR.