Updated: 12/28/2021

Antiarrhythmics

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  • 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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                      (M2.CV.17.4698) A 65-year-old man with hypertension and paroxysmal atrial fibrillation presents to his cardiologist for follow-up after recently starting metoprolol for rate control. His EKG shows an atrial rate of 260/min with ventricular rate of 50/min on an irregular baseline. An echocardiogram from his previous visit revealed no evidence of hypokinesis or hypertrophy with functionally intact valves. The patient does not drink alcohol and had no evidence of liver dysfunction in prior studies. What is the best medication for rhythm control in this patient?

                      QID: 108178

                      Verapamil

                      29%

                      (10/34)

                      Flecainide

                      29%

                      (10/34)

                      Procainamide

                      9%

                      (3/34)

                      Mexiletine

                      0%

                      (0/34)

                      Amiodarone

                      32%

                      (11/34)

                      M 7 B

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