title: [Vaughan Williams class IV antiarrhythmic drugs].
abstract: Vaughan Williams class IV antiarrhythmic drugs have Ca-channel blocking actions. Since L-type Ca-channels play key roles in regulating pulse conduction in atrioventricular node as well as in pathologically-depolarized myocardium, Ca-channel blockers known to modulate this type of Ca-channel (ICa,L) are used as antiarrhythmic agents. ICa,L channels have relatively high threshold potential (-40 mV) to activate and long-opening properties, and are enhanced by beta-adrenergic stimulation. Among three major ICa,L blockers, dihydropyridines such as nifedipine were found to bind to the channel from extracellular side. In contrast, verapamil and diltiazem interact with the channel from the cytoplasmic side, thereby causing rate-dependent block of ICa,L channels. This sideness of pharmacological action of the Ca-channel blockers determines an important therapeutic modality and their indication for tachyarrhythmias.
authors.affiliation: Third Department of Internal Medicine, Faculty of Medicine, Kyoto University.
authors.forename: M
authors.initials: M
authors.lastname: Horie
authors.forename: T
authors.initials: T
authors.lastname: Washizuka
authors.forename: S
authors.initials: S
authors.lastname: Ikeguchi
authors.forename: S
authors.initials: S
authors.lastname: Sasayama
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000145:classification / Q000494:pharmacology; D001145:Arrhythmias, Cardiac / Q000188:drug therapy* / Q000503:physiopathology; D002121:Calcium Channel Blockers; D006801:Humans
chemical_list: D000889:Anti-Arrhythmia Agents; D002121:Calcium Channel Blockers