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CARDIAC DRUG THERAPY - PART 7

IV thuốc đối kháng canxi ức chế kênh canxi hạn chế chậm canxi hiện tại một tranh cãi. Thay đổi từ EM Vaughan Williams. Phân loại các thuốc chống loạn nhịp. Sandhoe E, FlenstedJensen E, Olesen KH, eds. Hội nghị chuyên đề về rối loạn nhịp tim. Sodertalje, | 250 Cardiac Drug Therapy Table 14-1 Electrophysiologic Classification of Antiarrhythmic Drugs Class Drugs Duration of action potential I Membrane-stabilizing A. Quinidine Slightly prolonged slows inhibit fast sodium channel Disopyramide phase 0 of the action Restriction of sodium current Procainamide potential II Inhibit sympathetic stimulation B. Lidocaine Mexiletine Aprindine Phenytoin Tocainide C. Flecainide Lorcainide Encainide Propafenone Beta-blockers Shorteneda minimal slowing of phase 0 Unaffected or slight effect slow phase 0 III Delayed repolarization Amiodarone Prolonged as major action IV Calcium antagonists Inhibit slow calcium channel Restriction of calcium current Bretylium Bethanidine Clofilium Sotalol Verapamil Diltiazem Prolongation of the effective refractory period a Controversial. Modified from Vaughan Williams EM. Classification of antiarrhythmic drugs. In Sandhoe E Flensted-Jensen E Olesen KH eds. Symposium on Cardiac Arrhythmias. Sodertalje Sweden AB Astra 1970 p 449. CLASSIFICATION Antiarrhythmic drugs may be considered from three distinct points of view 1. According to their site of action. 2. According to their electrophysiologic action on isolated cardiac fibers classes I-IV as proposed by Vaughan Williams 1 Table 14-1 . Vaughan Williams indicated that class IB drugs are rapidly attached to sodium channels during the action potential. Thus few channels are available for activation at the commencement of diastole and the effective refractory period ERP is prolonged. During diastole however the drugs are rapidly detached. At the end of diastole most channels are drug free. Thus there is no slowing of conduction velocity in the ventricle or His-Purkinje system. Class IC drugs detach very slowly from their binding to the channels during diastole. This action eliminates some sodium channels producing slower conduction ERP is not prolonged. Class IA drugs are intermediate between classes IB and IC. Note that this classification is based on .