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

AIMS: 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. METHODS AND RESULTS: 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. CONCLUSIONS: 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.

Critical Assessment of the Concepts and Misconceptions of the Cardiac Conduction System over the Last 100 Years: The Personal Quest of Robert H. Anderson.

Anatomical concepts regarding the conduction system of the heart have been a matter of debate since pioneering work done at the beginning of the 20th century. Robert H. Anderson was actively involved in this field for half a century. We aimed to investigate how his own concepts evolved over time. We have assessed anatomical concepts relating to the cardiac conduction system appearing since the key contributions made in the initial decade of the 20th century, analyzing them from the perspective of Robert H. Anderson, particularly focusing on the anatomical aspects of structures such as accessory atrioventricular pathways, including the so-called Mahaim-type fibers, connections between the atrioventricular node and the atrial myocardium, and so-called "specialized" internodal atrial tracts. To accomplish this task, we have taken as our starting point the initial concepts published in the first decade of the century, along with those subsequently reported up to 1976, and assessing them in the light of our most recently published works. The concepts put forward by Robert Anderson with regard to atrioventricular nodal bypass tracts, atrioventricular nodal inputs, decrementally conducting accessory pathways, and "tracts" for internodal atrial conduction, have remained consistent along the time frame of half a century.