PO-02-178 ABLATION TISSUE HISTOLOGY AND CORRELATION WITH MAGNETIC RESONANCE IMAGING WITH A DIAMOND-BASED, TEMPERATURE-CONTROLLED RADIOFREQUENCY ABLATION

Abstract

A new catheter has been developed which uses diamonds embedded in the catheter tip to enable temperature-guided ablation. The degree to which subsequent Magnetic Resonance (MR) findings correlate with actual tissue pathology has never been assessed. To evaluate the correlation between MR imaging and lesions assessed by Gross pathology. 20 canines underwent evaluation, after ablation. 4 were studied acutely 4-6 hours after ablation, 8 animals were studied at a time of chronic assessment 4 weeks later, and 8 were studied at a time of chronic assessment 4 weeks later myocardial infarction creation. MR lesions were followed by intravenous gadolinium and 8-10% triphenyl tetrazolium chloride administration. Ex-vivo delayed contrast enhancement MR imaging on a 3 Tesla scanner (Signa HDxt, GE Healthcare) was performed followed by pathology examination after fixation in 10% formalin solution. Total of 111 lesions were created in LV and RV tissue. In the acute animals 30 deliveries were made to a temperature set-point of 50 or 60°C. The target temperatures were set at 60°C with 32 deliveries to healthy myocardium, and 8 to post-infarcted myocardium. Lesion size and characteristic are shown in table 1. The correlation between the actual lesion size and the MR contoured size is shown in Fig 1. In all animals taken together, MR proved to be an exceptional means of determining actual lesion size. While tissue histology, seen in the table, is more useful and accurate. Overall, the correlation R2 value is 0.72±0.11 (p<0.0001) in all groups. In individual groups, the correlation was 0.94±0.54 (p<0.0001) for acute, 0.48±0.13 (p<0.0001) for chronic healthy, and 0.97± 0.35 (p=0.0006) in infarcted tissue. Even with infarctions, the MR correlation remained consistent but lesions were smaller in infarcted myocardium. These data showed the characteristics of lesion size of correlation to energy delivered. MR with gadolinium is a very useful means of identifying actual lesion size in situ. This correlates well with actual tissue findings and disclose that heat penetration in infarcted tissue is less robust as seen with other catheter systems.