[Mechanisms of action of antiarrhythmics in cardioversion of atrial fibrillation and atrial flutter].
The mechanisms of action of antiarrhythmic drugs at atrial level are multiple. Antiarrhythmics may act at three levels in the prevention of paroxysmal atrial fibrillation: on the arrhythmogenic atrial substrate, the initiating extrasystoles including those of the pulmonary veins, and in the modulation of the autonomic nervous system. However, there are many modes of initiation which are not well understood so that the preventive role of the antiarrhythmic drugs remains imprecise. Cardioversion of persistent atrial fibrillation has been better analysed in healthy hearts: Class I antiarrhythmics in particular, despite their depressive effects on the conduction which are potentially arrhythmogenic, are beneficial by decreasing the number of reentry circuits, prolonging the atrial refractory period on short cycles and, paradoxically, by increasing the period of excitability in AF. All have a preferential action on anisotropic conduction, especially at the pivotal point of reentry. On the other hand, their role in electrophysiological remodelling in the prevention of immediate recurrences and in pathological atria, remains poorly understood. As for atrial flutter, despite many clinical and experimental studies with antiarrhythmics, the current predominant role of radiofrequency ablation greatly limits the value of these pharmacological studies.
Davy
J M
JM
Service de cardiologie B, hôpital Arnaud de Villeneuve, 371, av. du Doyen Gaston Giraud, 34295 Montpellier. jm-davy@chu-montpellier.fr
Raczka
F
F
Beck
L
L
Piot
C
C
D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001281:Atrial Fibrillation / Q000188:drug therapy*; D001282:Atrial Flutter / Q000188:drug therapy*; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology; D004554:Electric Countershock; D006339:Heart Rate; D006801:Humans
D000889:Anti-Arrhythmia Agents