Widening of the excitable gap and enlargement of the core of reentry during atrial fibrillation with a pure sodium channel blocker in canine atria

• Published in: Circulation (New York, N.Y.) Vol. 107; no. 6; pp. 905 - 910
• Main Authors: KAWASE, Ayaka, IKEDA, Takanori, NAKAZAWA, Kazuo, ASHIHARA, Takashi, NAMBA, Tsunetoyo, KUBOTA, Tetsuya, SUGI, Kaoru, HIRAI, Hironori
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 18.02.2003; American Heart Association, Inc
• Subjects: Acetylcholine; Animals; Atrial Fibrillation - chemically induced; Atrial Fibrillation - drug therapy; Atrial Fibrillation - physiopathology; Biological and medical sciences; Body Surface Potential Mapping; Cardiac dysrhythmias; Cardiology. Vascular system; Dogs; Dose-Response Relationship, Drug; Electrocardiography; Electrophysiologic Techniques, Cardiac; Female; Heart; Heart Atria - drug effects; Heart Atria - physiopathology; In Vitro Techniques; Lidocaine - analogs & derivatives; Lidocaine - pharmacology; Male; Medical sciences; Membrane Potentials - drug effects; Sodium Channel Blockers - pharmacology; Pharmacologic test; Arrhythmia; sodium channel blockers; Electrophysiology; Cardiovascular disease; Ionic channel; Heart disease; Sodium ion; Antagonist; Dog; Anilide; Fissipedia; Atrium; Carnivora; excitable gap; mapping; Pathophysiology; Atrial fibrillation; Exploration; Excitability disorder; Pilsicainide; Wavefront; Vertebrata; Mammalia; Animal
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/01.CIR.0000050148.72502.3A

This study aimed to assess the effects of pilsicainide, a pure sodium channel blocker, on electrophysiological action and wavefront dynamics during atrial fibrillation (AF). In a newly developed model of isolated, perfused, and superfused canine atria (n=12), the right and left endocardia were mapped simultaneously by use of a computerized mapping system. AF was induced with 1 to 5 micromol/L acetylcholine. The antifibrillatory actions of pilsicainide on AF cycle length (AFCL), refractory period (RP), conduction velocity (CV), excitable gap (EG), and the core of the mother rotor were studied. The RP was defined as the shortest coupling interval that could capture the fibrillating atrium. The EG was estimated as the difference between the AFCL and RP. At baseline, multiple wavefronts were observed. After 2.5 microg/mL infusion of pilsicainide, all preparations showed irregular activity, and AF was terminated in 2 preparations. The AFCL and RP were prolonged, and CV was decreased significantly. The EG was widened (147%; P<0.01), and the core perimeter was increased (100%; P<0.01). Increasing the dosage either terminated AF (6 preparations) or converted to organized activity (ie, atypical atrial flutter) (4 preparations). On the maps, all "unorganized" AFs were terminated with the excitation of the core of the mother rotor by an outside wavefront, whereas in preparations with atrial flutter, pilsicainide did not terminate its activity. Widening of the EG by pilsicainide facilitates the excitation of the core of the mother rotor, leading to the termination of AF. In some experiments, pilsicainide converts AF to persistent atrial flutter.