Abstract 4113: In-Vitro Characterization of Ablation Lesions Using Oct

Abstract

Radiofrequency ablation (RFA) is a clinical procedure that destroys tissue to cure cardiac arrhythmias. Presently, there is no direct method to monitor RFA lesion formation in real-time. Real time direct monitoring of the tissue could guide ablation and prevent complications such as tissue disruption that leads to perforation. Optical coherence tomography (OCT) provides real-time subsurface imaging with high spatial resolution in three dimensions. We hypothesized that OCT can distinguish necrotic ablated tissue from viable cardiac tissue. Freshly excised right ventricular wedges from swine were placed in a bath with phosphate buffered saline (PBS) maintained at 37°C with super-perfusion flow. RFA lesions were created with a temperature controlled (70°C) protocol, maximum delivered power of 50W for 10, 20, 30, and 60 seconds. Endocardial lesions were created using a 7Fr, 4mm tip RFA catheter. OCT imaging was conducted on a system with a 1310 nm light source and 10μm axial and 18 μm lateral resolution. Staining with 0.1% triphenyltetrazolium chloride in PBS for 15 minutes was used to confirm necrosis and quantify lesion size. The single scattering model of OCT images was used to extract three parameters (attenuation, backscattering, and correlation) to give an indication of tissue scattering, reflectivity, and heterogeneity respectively. OCT images of control (n=26) and ablated tissue (n=87) were analyzed with OCT. Viable tissue had a banding appearance due to the bifriengence property of highly organized myocardial tissue, absent in necrotic tissue caused by ablation. RFA lesions were characterized by increased imaging depth, increased scattering, and a heterogeneous appearance in OCT images. The real-time changes in tissue were detected after onset of ablation. 29 tissue samples had early detection of crater formation and tissue disruption before any adverse effect could occur. The correlation and attenuation coefficients of necrotic tissue were significantly smaller than viable tissue (p<0.01). Using OCT imaging, healthy endocardium and myocardium can be readily distinguished from necrotic tissue produced by RFA. This real-time monitoring may guide ablation by allowing the operator to see ablated tissue before an adverse event can occur.