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Updated: Dec 28 2021

Antiarrhythmics

  • 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
      • class I drugs are Na+ channel blockers
      • class II drugs are β-blockers
      • class III drugs are K+ channel blockers
      • class IV drugs are Ca2+ channel blockers
    • Antiarrhythmics
      Class
      MneumonicMechanism
      Class IANa+ channel blockers
      • DoubleQuarterPounder
        • Disopyramide
        • Quinidine
        • Procainamide
        • ↑ Action potential (AP)
        • ↑ Effective refractory period (ERP)
        • ↑ QT interval
          Class IBNa+ channel blockers
          • Lettuce andMayo
            • Lidocaine
            • Mexiletine
            • ↓ AP
            • ↓ ERP
            • Affects ischemic or depolarized tissue
              • hence, great for post-myocardial infarction arrhythmias
              Class ICNa+ channel blockers
              • FriesPlease
                • Flecainide
                • Propafenone
              • ↑ ERP in atrioventricular node but not in ventricular tissue
              Class II β-blockers
              • Drug name - lol
              • Selective β-blockers
                • metoprolol, esmolol, propranolol, atenolol, and timolol
                • esmolol is the most short-acting
              • Nonselective α- and β-blockers
                • carvedilol
                • labetalol
                • ↓ Sinoatrial and atrioventricular nodal activity
                  • ↓ cAMP and ↓ Ca2+ currents
                  • ↓ slope of phase 4
                • ↑ PR interval
                  Class III K+channel blockers
                  • AIDS
                    • Amiodarone
                    • Ibutilide
                    • Dofetilide
                    • Sotalol
                    • ↑ AP
                    • ↑ ERP
                    • ↑ QT interval
                      Class IV Ca2+channel blockers
                      • Class IVDrugs
                        • Verapamil
                        • Diltiazem
                        • ↑ 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
                          • these drugs slow down conduction and ↓ slope of phase 0 depolarization
                        • Class IA (disopyramide, quinidine, and procainamide)
                          • clinical use
                            • atrial and ventricular arrhythmias
                              • re-entrant and ectopic supraventricular tachycardias (SVTs) and ventricular tachycardias (VTs)
                          • toxicity
                            • thrombocytopenia
                            • torsades de pointes
                              • from ↑ QT interval
                            • heart failure (disopyramide)
                            • headache (quinidine)
                            • tinnitus (quinidine)
                            • reversible systemic lupus erythematosus-like syndrome (procainamide)
                        • Class IB (lidocaine and mexiletine)
                          • clinical use
                            • post-myocardial infarction and other ventricular arrhythmias
                            • digitalis-induced arrhythmias
                          • toxicity
                            • cardiovascular depression
                            • central nervous system effects
                        • Class IC (flecainide and propafenone)
                          • clinical use
                            • SVTs, including atrial fibrillation
                          • toxicity
                            • proarrhythmic
                            • contraindicated in structural and ischemic heart disease, especially post-myocardial infarction
                      • Class II - β-Blockers
                        • Clinical use
                          • SVTs, including atrial fibrillation and atrial flutter
                        • Toxicity
                          • impotence
                          • exacerbation of lung disease (chronic obstructive pulmonary disease and asthma)
                          • cardiovascular effects
                            • bradycardia
                            • atrioventricular block
                            • heart failure
                          • central nervous system effects
                            • sedation
                            • sleep disturbance
                          • dyslipidemia (metoprolol)
                          • exacerbate Prinzmetal angina (propranolol)
                        • Treatment for overdose of β-blockers
                          • saline
                          • atropine
                          • glucagon
                      • Class III - K+ Channel Blockers
                        • Clinical use
                          • atrial fibrillation
                          • atrial flutter
                          • VTs
                            • especially amiodarone and sotalol
                        • Toxicity
                          • torsades de pointes (sotalol and ibutilide)
                          • excessive β-blockade (sotalol)
                          • amiodarone
                            • no risk of torsades de pointes
                            • check pulmonary function tests (PFTs), liver function tests (LFTs), and thyroid function tests (TFTs)
                              • pulmonary fibrosis and interstitial pneumonitis
                              • hepatotoxicity
                              • thyrotoxicity, leading to hypo- or hyperthyroidism depending on patient's baseline thyroid function or any pre-existing thyroid disease
                            • blue/gray skin deposits and photodermatitis
                            • corneal deposits
                            • neurologic effects
                            • gastrointestinal effects
                            • cardiovascular depression
                              • bradycardia
                              • heart block
                              • heart failure
                      • Class IV - Ca2+ Channel Blockers
                        • Clinical use
                          • atrial fibrillation
                          • prevention of SVT
                        • Toxicity
                          • constipation
                          • flushing
                          • edema
                          • cardiovascular depression
                            • heart failure
                            • atrioventricular block
                            • sinus node depression
                      • Other Anti-Arrhythmics
                        • Adenosine
                          • mechanism
                            • ↑ K+ out of cells causes hyperpolarization of the cell and decreased atrioventricular node conduction
                            • very short-acting (approximately 15 seconds)
                          • clinical use
                            • diagnosing and/or terminating SVT
                          • toxicity
                            • flushing
                            • hypotension
                            • chest pain
                            • sense of impending doom
                            • bronchospasm
                        • Mg2+
                          • clinical use
                            • torsades de pointes
                            • digoxin toxicity
                          • toxicity
                            • lethargy
                            • bradycardia
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