caa a22 4500 605509735 CHVBK 20210128100642.0 cr unu---uuuuu 210128e20150201xx s 000 0 eng 10.1007/s10877-014-9570-x doi (NATIONALLICENCE)springer-10.1007/s10877-014-9570-x Thoracic impedance measures tissue characteristics in the vicinity of the electrodes, not intervening lung water: implications for heart failure monitoring [Elektronische Daten] [Christopher Charles, Miriam Rademaker, Iain Melton, Dan Gutfinger, Neal Eigler, Fujian Qu, Richard Troughton] The rationale for intrathoracic impedance (Z) detection of worsening heart failure (HF) presupposes that changes in Z reflect changes in pulmonary congestion, but is confounded by poor specificity in clinical trials. We therefore tested the hypothesis that Z is primarily affected by tissue/water content in proximity to electrodes rather than by lung water distribution between electrodes through the use of a new computational model for deriving the near-field impedance contributions from the various electrodes. Six sheep were implanted with a left atrial pressure (LAP) monitor and a cardiac resynchronization therapy device which measured Z from six vectors comprising of five electrodes. The vector-based Z was modelled as the summation of the near-field impedances of the two electrodes forming the vector. During volume expansion an acute increase in LAP resulted in simultaneous reductions in the near-field impedances of the intra-cardiac electrodes, while the subcutaneous electrode showed several hours of lag (all p<0.001). In contrast, during the simulated formation of device-pocket edema (induced by fluid injection) the near-field impedance of the subcutaneous electrode had an instantaneous response, while the intra-cardiac electrodes had a minimal inconsistent response. This study suggests that the primary contribution to the vector based Z is from the tissue/water in proximity to the individual electrodes. This novel finding may help explain the limited utility of Z for detecting worsening HF. The Author(s), 2014 Implantable monitors nationallicence Hemodynamics nationallicence Left atrial pressure nationallicence Charles Christopher Christchurch Heart Institute, University of Otago, P.O. Box 4345, Christchurch, New Zealand aut Rademaker Miriam Christchurch Heart Institute, University of Otago, P.O. Box 4345, Christchurch, New Zealand aut Melton Iain Christchurch Heart Institute, University of Otago, P.O. Box 4345, Christchurch, New Zealand aut Gutfinger Dan Implantable Electronic Systems Division, St. Jude Medical, Sylmar, CA, USA aut Eigler Neal Implantable Electronic Systems Division, St. Jude Medical, Sylmar, CA, USA aut Qu Fujian Implantable Electronic Systems Division, St. Jude Medical, Sylmar, CA, USA aut Troughton Richard Christchurch Heart Institute, University of Otago, P.O. Box 4345, Christchurch, New Zealand aut Journal of Clinical Monitoring and Computing Springer Netherlands 29/1(2015-02-01), 65-76 1387-1307 29:1<65 2015 29 10877 https://doi.org/10.1007/s10877-014-9570-x text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10877-014-9570-x text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Charles Christopher Christchurch Heart Institute, University of Otago, P.O. Box 4345, Christchurch, New Zealand aut NATIONALLICENCE 700 1- Rademaker Miriam Christchurch Heart Institute, University of Otago, P.O. Box 4345, Christchurch, New Zealand aut NATIONALLICENCE 700 1- Melton Iain Christchurch Heart Institute, University of Otago, P.O. Box 4345, Christchurch, New Zealand aut NATIONALLICENCE 700 1- Gutfinger Dan Implantable Electronic Systems Division, St. Jude Medical, Sylmar, CA, USA aut NATIONALLICENCE 700 1- Eigler Neal Implantable Electronic Systems Division, St. Jude Medical, Sylmar, CA, USA aut NATIONALLICENCE 700 1- Qu Fujian Implantable Electronic Systems Division, St. Jude Medical, Sylmar, CA, USA aut NATIONALLICENCE 700 1- Troughton Richard Christchurch Heart Institute, University of Otago, P.O. Box 4345, Christchurch, New Zealand aut NATIONALLICENCE 773 0- Journal of Clinical Monitoring and Computing Springer Netherlands 29/1(2015-02-01), 65-76 1387-1307 29:1<65 2015 29 10877