Optical Tissue Interrogation Catheter that Provides Real-Time Monitoring of Catheter-Tissue Contact and RF Lesion Progression using NADH Fluorescence
Abstract
Background: Suboptimal radiofrequency ablation (RF) lesions may result from either poor catheter tip-tissue contact, or inadequate energy deposition resulting in discontinuous or non-transmural lesions. A system and method were assessed for using real-time optical tissue interrogation within the NADH fluorescence range to evaluate contact between the RF catheter tip and myocardium, monitor the progression of ablation lesions, linear lesions and evaluation of new multi-directional monitoring from the catheter tip in real time during RF delivery.
Methods And Results: An irrigated RF ablation catheter incorporating imaging optics (LuxCath, LLC) was inserted transvenously into the heart chambers of 9 anesthetized swine. Light (360 + /-25nm) was delivered into the cardiac tissue. The fluoresced response from 370 nm to 660 nm was captured via spectrometer and analyzed in real time. Spectral data was acquired pre, during, and post formation of the RF lesions. Two types of plots were created for each lesion: intensity (in counts) vs. wavelength (nm), and 465nm peak amplitude (normalized) vs. time (sec).
Myocardium fNADH response over time during ablation is an indication of tip to tissue contact. fNADH correlates with the physiology of the ablation lesions, healthy tissue having the highest fluorescence intensity and ablated tissue having the lowest fNADH. A smooth response plot during lesion creation indicates stable tip to tissue contact. A sharper response is an indication of intermittent or shifting tip to tissue contact.
Overlay of the spectral plots of tissue fluorescence during ablations demonstrate a stable diminishing signature in the plotted spectra as an indication of catheter stability and successful lesion creation. Shifting signatures indicate tip movement during an ablation. When the tip shifts from predominantly myocardium to an area with more collagen or elastin the spectral plot has a characteristic change that helps to characterize the type of tissue at the catheter tip. Myocardial fNADH response declined by 70% +/- 10 % during 30 sec of RF ablation, with a 60% reduction occurring within the first 15 sec with the use of multi-view catheter on the last three experiments. Necropsy confirmed that the information regarding catheter contact and stability obtained by these optical means was a good predictor of lesion quality. Signatures indicating stable contact with reduction in fNADH resulted in high quality lesions. Signatures indicating unstable catheter contact resulted in poor or no lesion formation. Linear lesions were easily monitored during RF ablation.
Conclusions: Real-time optical tissue characterization provides excellent assessment of electrode-tissue contact and lesion progression during RF delivery. New catheter modifications allow for distal and lateral monitoring of fNADH. Linear lesion formation was easily monitored. The catheter also provides highly valuable information regarding the myocardium and collagen tissue composition at the site of catheter tip
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