Intracardiac myocardial elastography for lesion quantification in cardiac radiofrequency ablation

Radiofrequency ablation of the myocardium is used to treat various cardiac arrhythmias. The size, spacing, and transmurality of lesions have been shown to affect the success of the ablation procedure; however, there is currently no method to directly image the size and formation of ablation lesions in real time. Intracardiac myocardial elastrography has been used previously to image the reduction in end-systolic strain in the ablated region as a result of the lesion formation. However, the relationship between end-systolic strain change and lesion size has not been investigated. In this study, a large animal model is used to establish a relationship between the area affected by the strain reduction and lesion volume. Ablation lesions (n=10) were created in the left ventricular epicardium in five anesthetized canines. A clinical intracardiac echocardiography machine was programmed to emit a custom diverging beam sequence at 600 Hz and used to image the ablation site before and after the induction of a lesion. Cumulative strains were estimated over systole using a normalized cross-correlation displacement algorithm and a Savitzky-Golay strain kernel. The reduction in strain as a result of the ablation was computed by comparing cumulative end-systolic strains before and after ablation. Lesion volume was also measured ex vivo and compared to the area of significant strain change (>8% reduction) for each lesion. A good correlation was found between the area of significant strain change and lesion volume (r 2 = 0.86). These results indicate that end-systolic strain measured using ME can be used to estimate the size of lesions induced during an RF ablation procedure, potentially assisting clinicians in lesion formation assessment during the procedure.