Abstract P333: A Study of Miniature Catheters' Spatial Electric Field Heterogeneity During Murine Cardiac Catheterizations

Abstract

Conductance catheters allow real-time quantification of hemodynamics, allowing cardiac functional characterization, an important predictor of long-term prognosis in cardiac disease. The technique’s accuracy is, however, inherently limited by the signal contribution from surrounding structures (spatially and temporally varying). Despite prior attempts to quantify this effect (known as parallel conductance) no prior study assessed the spatial heterogeneity of the catheter's E-field. This study quantifies the E-field penetration pattern, accounting for tissue properties and geometry. Ten C57BL/6J mice were induced and maintained with 1.5% isoflurane mixed in 100% O 2 . One C57BL/6J mouse underwent a right carotid catheterization for placement of a 1.4 Fr Pressure-Volume Millar catheter in the left ventricle (LV), followed by microCT imaging (80kV/160mA/10ms exposure/240 projections/rotation angle=1.5 o ). Multiphase MRI was performed using a 4D radial spiral pulse sequence (TE=300μs/TR=2.4ms/BW=125kHz/flip angle=45 o /110μm 3 resolution). Segmentation allowed LV myocardial and blood region extractions from MRI and construction of finite element End-Diastolic and End-Systolic models. The catheter’s orientation in the LV was determined from micro-CT image data renditions. Generated LV and blood models were then imported in the software XFdtd and electrical properties were assigned for all materials. Simulations used a 20 μA, 20 kHz sinusoidal current, and ran for a lump component equivalent and a constructed blood-myocardial geometrical model. Specific absorption rate (SAR) maps yielded total tissue deposited power. Simulations show that the catheter’s E-field in lump component and geometrical models, drops to 10% of its peak value at 0.4-0.6mm, and 1.1-2mm, respectively, away from the excitation electrodes. SAR maps yielded a <1% power leakage into surrounding structures at two different myocardial permittivity values of ε r =11844 and 38615. Results from this study map the spatial dependence of the generated catheter E-field. Spatial E-field maps indicate that the field is primarily confined within the ventricular chamber with a relatively uniform spatial pattern, and with <1% of the input power leaking in surrounding structures.