The mechanisms of atrial fibrillation.
In this article we have reviewed the mechanisms of atrial fibrillation (AF) with special emphasis on the thoracic veins. Based on a number of features, the thoracic veins are highly arrhythmogenic. The pulmonary vein (PV)-left atrial (LA) junction has discontinuous myocardial fibers separated by fibrotic tissues. The PV muscle sleeve is highly anisotropic. The vein of Marshall (VOM) in humans has multiple small muscle bundles separated by fibrosis and fat. Insulated muscle fibers can promote reentrant excitation, automaticity, and triggered activity. The PV muscle sleeves contain periodic acid-Schiff (PAS)-positive large pale cells that are morphologically reminiscent of Purkinje cells. These special cells could be the sources of focal discharge. Antiarrhythmic drugs have significant effects on PV muscle sleeves both at baseline and during AF. Both class I and III drugs have effects on wavefront traveling from PV to LA and from LA to PV. Separating the thoracic veins and the LA with ablation techniques also prevents PV-LA interaction. By reducing PV-LA interaction, pharmacological therapy and PV isolation reduce the activation rate in PV, intracellular calcium accumulation, and triggered activity. Therefore, thoracic vein isolation is an important technique in AF control. We conclude that thoracic veins are important in the generation and maintenance of AF.
Chen
Peng-Sheng
PS
Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA. chenp@cshs.org
Chou
Chung-Chuan
CC
Tan
Alex Y
AY
Zhou
Shengmei
S
Fishbein
Michael C
MC
Hwang
Chun
C
Karagueuzian
Hrayr S
HS
Lin
Shien-Fong
SF
D000375:Aging; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D001281:Atrial Fibrillation / Q000188:drug therapy / Q000503:physiopathology*; D001683:Biological Clocks / Q000187:drug effects; D022062:Electrophysiologic Techniques, Cardiac; D006801:Humans; D008022:Ligaments / Q000503:physiopathology; D011342:Procainamide / Q000494:pharmacology; D011667:Pulmonary Veins / Q000187:drug effects / Q000503:physiopathology*; D013449:Sulfonamides / Q000494:pharmacology; D014683:Vena Cava, Superior / Q000503:physiopathology
D000889:Anti-Arrhythmia Agents; D013449:Sulfonamides; C067192:ibutilide; D011342:Procainamide