Impedance measurement to assess epicardial fat prior to RF intraoperative cardiac ablation: a feasibility study using a computer model.

Radiofrequency (RF) cardiac ablation is used to treat certain types of arrhythmias. In the epicardial approach, efficacy of RF ablation is uncertain due to the presence of epicardial adipose tissue interposed between the ablation electrode and the atrial wall. We planned a feasibility study based on a theoretical model in order to assess a new technique to estimate the quantity of fat by conducting bioimpedance measurements using a multi-electrode probe. The finite element method was used to solve the electrical problem. The results showed that the measured impedance profile coincided approximately with the epicardial fat profile measured under the probe electrodes and also that the thicker the epicardial fat, the higher the impedance values. When the lateral fat width was less than 4.5 mm, the impedance values altered, suggesting that measurements should always be conducted over a sizeable fat layer. We concluded that impedance measurement could be a practical method of assessing epicardial fat prior to RF intraoperative cardiac ablation, i.e. 'to map' the amount of adipose tissue under the probe.