Transmural Versus Nontransmural In Situ Electrical Impedance Spectrum for Healthy, Ischemic, and Healed Myocardium

Abstract

Abstract-Electrical properties of myocardial tissue are anisotropic due to the complex structure of the myocardial fiber orientation and the distribution of gap junctions. For this reason, measured myocardial impedance may differ depending on the current distribution and direction with respect to myocardial fiber orientation and, consequently, according to the measurement method. The objective of this study is to compare the specific impedance spectra of the myocardium measured using two different methods. One method consisted of transmural measurements using an intracavitary catheter and the other method consisted of nontransmural measurements using a four-needle probe inserted into the epicardium. Using both methods, we provide the in situ specific impedance spectrum (magnitude and phase angle) of normal, ischemic, and infarcted pig myocardium tissue from 1 kHz to 1 MHz. Magnitude spectra showed no significant differences between the measurement techniques. However, the phase angle spectra showed significant differences for normal and ischemic tissues according to the measurement technique. The main difference is encountered after 60 min of acute ischemia in the phase angle spectrum. Healed myocardial tissue showed a small and flat phase angle spectrum in both methods due to the low content of cells in the transmural infarct scar. In conclusion, both transmural and nontransmural measurements of phase angle spectrum allow the differentiation among normal, ischemic, and infarcted tissue.

Towards on line monitoring the evolution of the myocardium infarction scar with an implantable electrical impedance spectrum monitoring system

“…A systematic increase of the initial magnitude can be observed. This is coherent with the previously described impedance increase in the acute ischemia [8] but can also be due to the patch and electrodes integration with the tissue. Then comes a maintenance phase.…”

Development of Bioactive Patch for Maintenance of Implanted Cells at the Myocardial Infarcted Site

“…Immunophenotypical characterization of the cells revealed a mesenchymal stem-cell-(MSC-) like pattern, with a high percentage of subATDPCs staining strongly positive for CD105, CD44, CD166, CD29, and CD90 and negative for CD106, CD45, and CD14 (Supplementary Figure 1B). Comparable to the case of bone marrow-derived [51,52]. c [52].…”

Changes in myocardial electrical impedance in human heart graft rejection

“…In the dog model [3] tissue impedance was measured by applying current pulses through intramyocardial screw-in electrodes, whereas in our clinical study we used sinusoidal currents through an electrocatheter. Due to the anisotropy characteristics of the myocardium, tissue impedance is influenced by the direction of the current flow [12]. Moreover, the mechanical and metabolic conditions of the non-working perfused neck-transplanted heart in the dog model are not comparable to those of a working systemically-connected human heart.…”