||Impedance cardiography in healthy children and children with congenital
heart disease: Improving stroke volume assessment
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||International Journal of Psychophysiology
||Impedance cardiography, Stroke volume, Children, Congenital heart disease, Pre-ejection period, Left ventricular ejection time
||Introduction: Stroke volume (SV) and cardiac output are important measures in the clinical evaluation of cardiac
patients and are also frequently used in research applications. This study was aimed to improve SV scoring
derived from spot-electrode based impedance cardiography (ICG) in a pediatric population of healthy volunteers
and patients with a corrected congenital heart defect.
Methods: 128 healthy volunteers and 66 patients participated. First, scoring methods for ambiguous ICG signals
were optimized to improve agreement of B- and X-points with aortic valve opening/closure in simultaneously
recorded transthoracic echocardiography (TTE). Building on the improved scoring of B- and X-points, the
Kubicek equation for SV estimation was optimized by testing the agreement with the simultaneously recorded SV
by TTE. Both steps were initially done in a subset of the sample of healthy children and then validated in the
remaining subset of healthy children and in a sample of patients.
Results: SV assessment by ICG in healthy children strongly improved (intra class correlation increased from 0.26
to 0.72) after replacing baseline thorax impedance (Z0) in the Kubicek equation by an equation
(7.337–6.208 ? dZ/dtmax), where dZ/dtmax is the amplitude of the ICG signal at the C-point. Reliable SV assessment
remained more difficult in patients compared to healthy controls.
Conclusions: After proper adjustment of the Kubicek equation, SV assessed by the use of spot-electrode based ICG
is comparable to that obtained from TTE. This approach is highly feasible in a pediatric population and can be
used in an ambulatory setting.