Effect multi-electrode ablation catheter angle on electrode-tissue contact measurement

Abstract

Introduction Sudden cardiac death is one of the major deaths worldwide. Several treatments are available to lower risks of sudden cardiac deaths. Atrial fibrillation is one of the leading causes for sudden cardiac deaths. Atrial fibrillation can be treated with drugs or with procedures or surgeries. Catheter ablation is one of these procedures. With the use of radiofrequency, the area in the heart causing the disrupting of the signal pathway and therefore causing the atrial fibrillation can be restored. When performing the ablation, the force on the heart tissue and insert angle of the catheter tip can influence the results of the catheter ablation. In this paper we investigate whether the impedance readout can be used to determine the force and the angle the multielectrode catheter tip is exerted on a phantom tissue. Methods To research the impedance readout with respect to the insert angle and force an experimental setup was designed. The electrodes of a catheter were connected to a HP impedance analyzer (HP 4192A). This catheter was guided through a 3D print with hollow tubes (90, 60, 45 and 30 degrees) to achieve the desired insert angle on a phantom. The 3D print is mounted to a linear stage to control the movement of the catheter with millimeter precision movement. The catheter was pressed onto a phantom. Cardiac phantoms were made with the base material Gellan Gum, Agar and PVA. The phantom was put in a container with a skinpatch counter electrode attached to it to be able to measure the impedance change. Below the container a scale is placed to readout the force that is being exerted on the phantom. Results Samples with base materials as Gellan Gum, Agar and PVA were made and the catheter was being exerted on it with various insert angles. Impedance change with increasing force and varying insert angles were recorded and graphs were taken out of the data that is being recorded with the use of Excel. The data has been taken from fresh made samples, 1 week old samples and 2 weeks old samples. From the graphs the relative impedance increase decreases when the insert angle is reduced from 90 to 30 degrees. Conclusion Impedance can be used to determine how much pressure is being exerted on a heart tissue. However, the catheter that approaches the heart tissue will have different insert angles. The impedance change is dependent on the various insert angles. Therefore it is not sure if this impedance change method can be used to determine the force that is being exerted on the heart tissue in a reliable way when the catheter tip angle is unknown.