Application of computer modelling and lead field theory in developing multiple aimed impedance cardiography measurements

Conventional impedance cardiography (ICG) methods estimate parameters relat ed to the function of the heart from a single waveform that reflects an int egrated combination of complex sources. We have previously developed method s and fools for calculating measurement sensitivity distributions of ICG el ectrode configurations. In this study, the methods were applied to investig ate the prospects of recording multiple aimed ICG waveforms utilizing the 1 2-lead electrocardiography (ECG) electrode locations. Three anatomically re alistic volume conductor models were used: one based on Visible Human Man c ryosection data and two on magnetic resonance (MR) images representing end diastolic and end systolic phases of the cardiac cycle. Based on the sensit ivity distributions obtained, 236 electrode configurations were selected fo r preliminary clinical examination on 12 healthy volunteers and 9 valvular patients. The model study suggested that a variety of configurations had cl early enhanced sensitivity to the cardiovascular structures as compared to conventional ICGs. Simulation data and clinical experiments showed logical correspondence supporting the theoretically predicted differences between t he configurations. Recorded 12-lead ICG signals had characteristic waveform s and landmarks not coinciding with those of conventional ICG. Furthermore, configurations showing resemblance to invasive data and morphological vari ations in disease are of interest. The results indicate the applicability o f the modelling approach in developing ICG measurement configurations. Howe ver, the level of clinical relevance and potential of the 12-lead method re mains to be explored in studies employing dynamic modelling and acquisition of invasive reference data.