High spatial resolution thermal mapping of radiofrequency ablation lesions using a novel thermochromic liquid crystal myocardial phantom.

BACKGROUND Radiofrequency (RF) ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro ablation lesions. METHODS AND RESULTS The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF ablations were performed. This comprised 17 ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be <300 μm. CONCLUSIONS High spatial resolution thermal mapping of in vitro RF lesions with spatial resolution of at least 300 μm is possible using a thermochromic liquid crystal myocardial phantom model, with a good correlation to in vivo RF ablations. This model may be useful for assessing the thermal characteristics of RF lesions created using different ablation parameters and catheter technologies.