Monitoring of laser effects on the conduction system by using an open-irrigated electrode-laser mapping and ablation catheter: laser catheter mapping

To assess the laser effects on the conduction system in dog hearts by monitoring potential amplitudes (PA) in the focused local electrograms (LEG) recorded via pin electrodes (PEs) from the tip of an open-irrigated electrode-laser mapping and ablation (ELMA) catheter. A total of 54 mapping guided laser impacts (continuous wave Nd:YAG 1064 nm), at 15 W, irrigation rate 30 mL/min, one per dog, were aimed at the sinus nodal (SN) (n = 20) and atrioventricular (AV) nodal (n = 24) areas, and at the His bundle and fascicles (n = 5, each). Laser effects were assessed by monitoring of PA in the bipolar focused LEGs. Electrophysiological and electropharmacological tests were performed prior to, immediately following, and 3-11 months after the experiments. Lesions were evaluated morphometrically and histopathologically. During laser application PA gradually dwindled. Radiation times limited to 3-5 s were allowed for recovery of PA without affecting functions of the conduction system. Graded laser application modulated SN and AV nodal functions permanently, or caused stable complete AV conduction block with a mapping-dependent escape rhythm and electrical axis deviation after radiation aimed at a fascicle. Monitoring of PAs recorded in the LEG via PE of the ELMA catheter during laser application is a unique claim of the laser method that enhances the assessment of local electrical activity and ablation efficacy. It allows the assessment of laser effects on the conduction system during ablation. By using the ELMA catheter described, long-term modulation of SN and AV nodal functions are achievable and unwanted complete heart block or fascicular block can be avoided.