Detection of (Reversible) Myocardial Ischemic Injury by Means of Electrical Bioimpedance

Abstract

The scope of this paper was to determine whether ischemic and reperfusion damage in cardiac surgery can be detected by measurement of electrical bioimpedance (EBI). Conventional pacing wires were replaced by pacing wires with sputtered iridium coating in order to reduce polarization associated with two-electrode impedance measurements. A custom-built bioimpedance analyzer (Osypka Medical GmbH, Berlin, Germany) measured the real part of impedance Re(Z) and the phase (ϕ) at three frequencies (1, 10, and 1000 kHz) and determined an extracellular space index (EZRI) as the quotient of Re(Z) at 1000 kHz and Re(Z) at 1 kHz. Our study included six patients (conventional coronary artery bypass graft, age 68.1 ± 8.3 years) subject to routine cardioplegic ischemia and reperfusion. Preischemic bioimpedance measurements were not impaired by interference of the beating heart. Intraischemically, bioimpedance at 1 kHz and phase at 10 kHz increased until opening of a bypass graft, which is probably induced by closure of gap junctions and cell swelling processes. After cross clamping, EZRI slowly decreased as an effect of mild cell swelling. After ischemia, values returned almost to baseline measurements, indicating sufficient reperfusion processes. Measurement of EBI correlates with myocardial ischemic injury and is applicable in a two-electrode setup providing low-polarization pacing wires.

Guidelines to electrode positioning for human and animal electrical impedance myography research

“…Among the limitations of this work, we assumed the electrodes were in direct contact with muscle to make the analysis feasible, an assumption that is satisfied in vitro 6263 and in vivo 496465666768. A more accurate impedance analysis should consider the anisotropic properties of the skin, subcutaneous fat and muscle layers69.…”

Towards Bio-impedance Based Labs: A Review

“…Myocardial ischemic reversibility is studied in Ref. [22], by applying two Iridium electrodes with low polarization effects. The objective is to define how infarcted myocardial cells can be recovered with success after an ischemia happens.…”

Age-related differences of intraischemic gap junction uncoupling in hearts during ischemia

“…According to the suggestions by Gersing 16 and Mellert et al, 17 electrical impedance spectroscopy can be used for the estimation of extracellular volume. With the assumption of a current exclusively running through the extracellular space at low frequencies and a current distribution in the intra-and extracellular space at high frequencies, we estimated the extracellular volume from the dielectric data by the extracellular space index (ECSI) in equation (3), which was defined as the quotient of the tissue conductivity at the lowest and the highest available frequency,…”