Modification of atrioventricular node transmission properties by intraoperative neodymium-YAG laser photocoagulation in dogs

• Published in: Journal of the American College of Cardiology 1991-03, Vol.17 (3), p.797-804
• Main Authors: Littmann, Laszlo, Svenson, Robert H., Tomcsanyi, Istvan, Hehrlein, Christoph, Gallagher, John J., Bharati, Saroja, Lev, Maurice, Splinter, Robert, Tatsis, George P., Tuntelder, Jan R.
• Format: Article
• Language: English
• Subjects: Animals; Atrioventricular Node - drug effects; Atrioventricular Node - pathology; Atrioventricular Node - physiopathology; Atrioventricular Node - surgery; Biological and medical sciences; Cardiac dysrhythmias; Cardiology. Vascular system; Dogs; Feasibility Studies; Female; Fibrosis; Follow-Up Studies; Heart; Heart Conduction System - drug effects; Heart Conduction System - pathology; Heart Conduction System - physiology; Heart Septum - pathology; Isoproterenol - pharmacology; Light Coagulation - methods; Male; Medical sciences; Propranolol - pharmacology; Retrospective Studies; Tachycardia, Atrioventricular Nodal Reentry - physiopathology
• ISSN: 0735-1097; 1558-3597
• DOI: 10.1016/S0735-1097(10)80200-1

The purpose of this study was to test the feasibility of neodymiumyttrium-aluminum-garnet (Nd-YAG) laser photocoagulation of the atrioventricular (AV) node to control the ventricular rate during rapid atrial rhythms without creating AV block. In 12 dogs on normothermic cardiopulmonary bypass, short laser pulses were delivered to an area between the coronary sinus orifice and the site of the most proximally recorded His deflection until second degree AV block occurred at a paced atrial rate of 200 beats/min. Long-term effects on AV node function were followed up for 3 months. Three animals developed chronic high grade AV block. In nine animals with preserved 1:1 conduction, the mean (±SEM) critical atrial cycle length resulting in AV node Wenckebach periodicity increased from 183 ± 6 to 261 ± 24 ms (+43%), the mean RR interval during induced atrial fibrillation increased from 248 ± 14 to 330 ± 27 ms (+32%) and the shortest RR interval during atrial fibrillation increased from 215 ± 11 to 275 ± 20 ms (+28%). Laser effects were not reversed by isoproterenol infusion. Histologic examination of the irradiated area showed fibrotic changes in the AV node and fatty metamorphosis. This study suggests that 1) graded Nd-YAG laser photocoagulation of the AV node region in dogs results in long-term modification of anterograde AV node transmission properties; 2) 1:1 conduction during sinus rhythm usually remains preserved, but ventricular rate during rapid atrial rhythms is chronically reduced; and 3) progression to high grade AV block occurs in a minority of animals. Laser modification of the AV node could become a form of nonpharmacologic heart rate control in patients with disabling atrial tachyarrhythmias.