A team lead by Dr. Stavros Demos (CBST researcher at Lawrence Livermore National Laboratory and Adjunct Prof. in the UC Davis Dept. of Urology) and Dr. Shiva Sharareh (Biosense Webster, Inc.) have conceived, developed and are in the process of commercially implementing a new medical catheter device for the treatment of atrial fibrillations. Until now, surgeons had limited feedback concerning characteristics of the RF modified tissue. This device is expected to dramatically improve safety and outcomes for these procedures. Over 100,000 such procedures are performed annually in this country. Biosense Webster Inc., a Johnson & Johnson company, is the leading manufacturer and supplier of RF catheters. A joint patent (US20060229515 A1) has been applied for and Biosense Webster, Inc. has obtained an exclusive license to practice this patent.

The novel technology developed in a partnership between CBST and Biosense Webster, Inc. uses an embedded fiber optic probe within a typical ablation catheter to characterize critical parameters in real-time during radio-frequency (RF) ablation of cardiac tissue. Modification of tissue by RF ablation produces significant changes in the tissue optical properties allowing this fiber optic assessment. RF ablation is used to treat atrial fibrillation, a heart condition that causes abnormal electrical signals, known as cardiac arrhythmias, to be generated in the endocardial tissue resulting in irregular beating of the heart. The RF energy is delivered locally via ablation electrode catheters that can be inserted percutaneously under local anesthesia into a femoral, brachial, subclavian, or internal jugular vein and positioned in the heart. Current methods have limited effectiveness in measuring RF produced lesion formation parameters in real-time or under associated adverse conditions.

The optical spectroscopy approach developed at CBST allows for critical parameters of the process leading to the formation of the lesion to be evaluated in real-time including such parameters as, catheter-tissue proximity, lesion formation, depth of penetration of the lesion, cross-sectional area of the lesion in the tissue, formation of char during the ablation, recognition of char from non-charred tissue, formation of coagulum around the ablation site, differentiation of coagulated from non-coagulated blood, differentiation of ablated from healthy tissue, and recognition of steam formation in the tissue for prevention of steam pop.  These assessments are accomplished by analyzing the spectral characteristics of the diffusely reflected light of selected wavelengths from the tip of the ablation catheter via the incorporation of fibers to deliver the illumination and collect the backscattered light.  

The drawing on the left shows an RF catheter that incorporates a fiber-optic probe for tissue characterization delivered to the right atrium of the heart. Drawings on the right show the RF catheter-tip in contact with the heart tissue, before (top) and after (bottom) delivery of RF energy. Tissue characterization using the fiber-optic probe will be able to determine catheter tissue separation, lesion formation and depth, formation of char, formation of coagulum, delineation of healthy vs. ablated tissue, and recognition of staem formation. Current systems provide limited or no information concerning these characteristics.

Some of this material was obtained from an abstract by Stavros Demos (CBST and Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA, 94551) and Shiva Sharareh (Biosense Webster, Inc., 3333 Diamond Canyon Road, Diamond Bar, California 91765 U.S.A). Images obtained from www.biosensewebster.com.

For more information about this article, please contact Dr. Stavros Demos (demos1@llnl.gov).