Copyright © 1992 by the European Society of Cardiology.
© 1992 The European Society of Cardiology
Improvement in intracardiac impedance volumes by field extrapolation
Research Department, Cardiac Pacemakers Inc., 4100 N. Hamline Ave., St. Paul, MN, U.S.A. 55112
Correspondence: R. W. Salo, Research Department, Cardiac Pacemakers Inc., 4100 N. Hamfine Avenue, SL Paul, MN, 55112-5798, U.S.A.
The measurement of volume by electrical impedance is complicated by non-homogeneous current distribution resulting from small current sources, by the irregular shape of the ventricle, and by loss of current to surrounding anatomical structures. A mathematical technique, field extrapolation, was developed to partially correct the current distribution. The technique mathematically transforms measured potentials into the potential distribution which would result from infinitely distant current sources. The linear correlation coefficient between impedance stroke volume or cardiac output using field extrapolation and thermodilution stroke volume or cardiac output was 0·83 (n = 86) in 11 dogs and 0·76 (n = 92) in 12 patients. The average linear correlation coefficient between impedance stroke volume and integrated aortic flow in four dogs was 0·83 ± 0·09 (n = 49) using field extrapolation.
Key Words: Intracardiac impedance conductance catheter field extrapolation