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Noninvasive measurement of cardiac output: two methods compared in patients with mitral regurgitation
N J van der Meer1, A Vonk Noordegraaf, O Kamp
1Department of Anesthesiology, Academic Medical Center, Amsterdam, The Netherlands.
Insights
Electrical impedance cardiography (EIC) provides reliable cardiac output (CO) estimations, even with mitral regurgitation. The impedance signal can also indicate valve pathology, improving CO measurement accuracy.
Area of Science:
- Cardiovascular Physiology
- Medical Instrumentation
Background:
- Electrical impedance cardiography (EIC) is used for estimating cardiac output (CO).
- Concerns exist regarding EIC's reliability, potentially due to cardiac valve pathology.
Purpose of the Study:
- To investigate if cardiac valve pathology affects the accuracy of CO estimations by EIC.
- To explore the utility of EIC-derived signals in identifying mitral regurgitation.
Main Methods:
- Compared CO measurements from EIC and echo Doppler (ED) in 26 patients.
- Assessed cardiac valve status using echocardiography and color Doppler.
- Analyzed EIC impedance signals (dZ/dt) in relation to valve status.
Main Results:
- Overall good correlation between EIC and ED for CO (r=0.85).
- Closer agreement in patients without valve pathology (nVP) (r=0.88).
- EIC reliably estimated CO even in patients with mild to moderate mitral regurgitation (MVR).
- Distinct differences in dZ/dt signals were observed between nVP and MVR groups.
- EIC signals indicated the presence of MVR.
Conclusions:
- EIC is a reliable method for CO estimation, even in the presence of mild to moderate mitral regurgitation.
- The impedance signal itself may serve as an indicator for mitral regurgitation, aiding in diagnosis.
Abstract:
In search for the origin of the less reliable cardiac output (CO) estimations by means of electrical impedance cardiography (EIC), the authors hypothesized 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 valve status was obtained by means of echocardiography and color Doppler flow, while CO was obtained by means of both methods. Seventeen patients had no valve pathology (nVP) while nine patients had mild to moderate mitral regurgitation (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 difference between the paired values. After division into an nVP and an MVR population, the results showed an even closer agreement between the CO values 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 groups. Although the agreement between ED and EIC was slightly lower in the MVR population, EIC reliably estimated CO, even in case of MVR. The impedance signal itself gave an indication for the existence of MVR.