Snapshot A 56-year-old man recently had a myocardial infarction. While in the hospital, he reported being lightheaded. An electrocardiogram revealed a ventricular arrhythmia. His past medical history included hypertension, diabetes mellitus type 2, and chronic kidney disease. He was initially given amiodarone with no effect. He was then given a medication known to be effective in post-myocardial infarction arrhythmias. (Mexiletine) Introduction Anti-arrhythmic medications are divided into 4 classes login to view 4 more bullets AntiarrhythmicsClassMneumonicMechanismClass IANa+ channel blockersDoubleQuarterPounderDisopyramideQuinidineProcainamide↑ Action potential (AP)↑ Effective refractory period (ERP)↑ QT intervalClass IBNa+ channel blockersLettuce andMayoLidocaineMexiletine↓ AP↓ ERPAffects ischemic or depolarized tissuehence, great for post-myocardial infarction arrhythmiasClass ICNa+ channel blockersFriesPleaseFlecainidePropafenone↑ ERP in atrioventricular node but not in ventricular tissueClass II β-blockersDrug name - lolSelective β-blockersmetoprolol, esmolol, propranolol, atenolol, and timololesmolol is the most short-actingNonselective α- and β-blockerscarvedilollabetalol↓ Sinoatrial and atrioventricular nodal activity↓ cAMP and ↓ Ca2+ currents↓ slope of phase 4↑ PR intervalClass III K+channel blockersAIDSAmiodaroneIbutilideDofetilideSotalol↑ AP↑ ERP↑ QT intervalClass IV Ca2+channel blockersClass IVDrugsVerapamilDiltiazem↑ ERP↑ PR interval↓ Conduction velocity Class I - Na+ Channel Blockers Double Quarter Pounder, with Lettuce and Mayo, and Fries Please for classes IA, IB, and IC respectively login to view 1 more bullet Class IA (disopyramide, quinidine, and procainamide) login to view 11 more bullets Class IB (lidocaine and mexiletine) login to view 6 more bullets Class IC (flecainide and propafenone) login to view 5 more bullets Class II - β-Blockers Clinical use login to view 1 more bullet Toxicity login to view 11 more bullets Treatment for overdose of β-blockers login to view 3 more bullets Class III - K+ Channel Blockers Clinical use login to view 4 more bullets Toxicity login to view 16 more bullets Class IV - Ca2+ Channel Blockers Clinical use login to view 2 more bullets Toxicity login to view 7 more bullets Other Anti-Arrhythmics Adenosine login to view 11 more bullets Mg2+ login to view 6 more bullets