In vitro experimental results using autofluorescence spectroscopy to assess RF ablation of bovine heart

Summary form only given. Radiofrequency (RF) cardiac ablation is the technique of choice for the treatment of asymptomatic arrhythmias [1]. It blocks the arhythmogenic signal via the isolation of the tissue regions with abnormal cardiac conduction. Due to the fact that ablation failure is often associated with inadequate lesion formation [2], we propose the use of a photonic biosensor to provide intraoperative feedback about the ablation's viability. LAKK-M's optical biosensor with UV-365 nm and Blue-450 nm [3] was used for recording the autofluorescence (AF) spectra in the range from 350 to 750 nm before and after RF ablation of the bovine myocardium. In vitro RF ablation of bovine cardiac tissue was endocardially performed, using the RF Smartablate HF Generator (Stockert GmbH) in collaboration with Queen Elizabeth Hospital (Birmingham, UK). The ablation power ranged from 20 to 40 W in 10 W increments applied for 20 and 40 sec intervals each time. These energy doses correspond to the clinically used ones for the ablation of Atrial Fibrillation, the most common arrhythmia [4, 5]. The fluorescence spectra were recorded by means of biosensor prior and after ablation as shown in Fig 1a. Based on the literature data, the main endogenous fluorophores of the heart tissue are NADH, FAD, collagen, and elastin [6], which could be changed after RF ablation. The recorded AF spectra corresponding to doses from 20 to 40 W were presented in Fig 1a. In order to confirm the effectiveness of ablation, the ablated tissue samples were histopathologically examined.We observe an increase in the fluorescence intensity along all the spectrum for the RF ablation energy range from 20 W, 20 sec to 40 W, 20 sec. High ablation dose (40 W, 40 sec) of the cardiac tissue resulted to low AF intensity (Fig 1a). The normalised coefficient of fluorescence(kf) [3] has an increasing trend for applied energy of 250 - 900 joules and a decreasing trend for 900 - 1400 joules as it was shown in Fig 1b. We compared our AF measurements with the macroscopic evaluation of the tissue. It was observed a correlation between AF intensity and measured volume of the heart tissue samples after ablation with different doses. Based on reported results it would be possible to develop an algorithmic models correlating the actual volume of ablation to the RF ablation energy and assist cardiosurgeons to adjust the energy and time of ablation.