Antiarrhythmic drugs

Last updated: 15.06.2020

Summary

Antiarrhythmic drugs are used to prevent recurrent arrhythmias and restore sinus rhythm in patients with cardiac arrhythmias. These drugs are classified based on their electrophysiological effect on the myocardium. Antiarrhythmic drugs do not improve the survival of patients with non-life-threatening arrhythmias and may increase mortality, particularly in patients with structural heart disease. They are associated with severe adverse effects, primarily due to their proarrhythmic effects on the myocardium. Patients who have received an intravenous antiarrhythmic should be monitored closely with serial ECGs. Several classes of antiarrhythmics, including beta blockers, calcium channel blockers, amiodarone, cardiac glycosides, and lidocaine, also have other medical uses, which are discussed in their respective learning cards.

Overview

Classes of antiarrhythmic drugs [1][2]
Class Drug group Mechanism of action Examples Use Adverse effects
Class IA antiarrhythmics
  • Fast sodium channel blockers
  • Reduce conduction velocity (negative dromotropy), particularly in depolarized tissue (e.g., during tachycardia)
  • Stabilize membrane
  • Categorized into 3 subgroups based upon their effects on the Na+ channel and the action potential (AP) duration
  • Moderate blockade of Na+ channels (intermediate association/dissociation)
  • Prolong AP duration (right shift)
  • Slow conduction velocity
  • Prolong effective refractory period (ERP)
  • Weak blockade of the K+ channel
  • Quinidine
  • Procainamide
  • Disopyramide
  • Ajmaline
Class IB antiarrhythmics
  • Weak blockade of Na+ channels (fast association/dissociation)
  • Shorten AP duration
  • Slow conduction velocity
  • No effect on or slight prolongation of ERP
  • Strongest effect on ischemic myocardium
Class IC antiarrhythmics
  • Strong blockade of Na+ channels (slow association/dissociation) → QRS prolongation
  • No to minimal effect on AP duration (no shift)
  • Slow conduction velocity
  • Prolong ERP in AV node and accessory tract
  • ERP unaffected in Purkinje and ventricular tissue
  • Flecainide
  • Propafenone
  • Proarrhythmogenic: contraindicated post-MI
Class II antiarrhythmic drugs
Class III antiarrhythmic drugs
  • Inhibit delayed rectifier potassium currents
  • Prolong QT interval
  • Prolong AP duration (reverse use dependence) and ERP
  • No effect on conduction velocity
Class IV antiarrhythmic drugs
  • Inhibit slow calcium channels
  • Decrease slope of phase 0 and 4slower conduction velocity → increased ERP
  • Prolong AV node repolarization
  • Prolong PR interval
Class V antiarrhythmic drugs
  • Variable mechanisms
  • See “Other antiarrhythmic drugs” below for details.
  • See below
  • See below

All antiarrhythmic drugs are also potentially proarrhythmic! Intravenous administration should only be performed with continuous cardiac monitoring!

References:[4][5][6][7][8]

Other antiarrhythmic drugs

Adenosine (drug) [1]

Avoid adenosine in patients with suspected pre-excitation tachycardia (e.g., WPW), because it may exacerbate the tachycardia via accessory pathway routes!

Digoxin

Magnesium sulfate [9][1]

If-channel blocker

IVabradine slows depolarization in phase IV.

References:[10][11][12][13][14][15][16][17][9]

References

  1. Le T, Bhushan V. First Aid for the USMLE Step 1 2015. McGraw-Hill Education ; 2014
  2. Jenkins B, McInnis M, Lewis C. Step-Up to USMLE Step 2 CK. Lippincott Williams & Wilkins ; 2015
  3. Le T, Bhushan V, Bagga HS. First Aid for the USMLE Step 2 CK. McGraw-Hill Medical ; 2009
  4. Kistler P. Focal atrial tachycardia. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. http://www.uptodate.com/contents/focal-atrial-tachycardia?source=search_result&search=atrial+tachycardia&selectedTitle=1~150. Last updated: October 16, 2015. Accessed: February 12, 2017.
  5. Manolis AS. Supraventricular Premature Beats. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/supraventricular-premature-beats. Last updated: March 14, 2016. Accessed: February 19, 2017.
  6. Kaplan. USMLE Step 1 Lecture Notes 2016: Pharmacology. New York, NY: Kaplan ; 2015
  7. Giardina EG, Zimetbaum PJ. Monitoring and Management of Amiodarone Side Effects. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/monitoring-and-management-of-amiodarone-side-effects. Last updated: February 13, 2017. Accessed: April 5, 2017.
  8. Makielski JC. Myocardial action potential and action of antiarrhythmic drugs. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/myocardial-action-potential-and-action-of-antiarrhythmic-drugs. Last updated: September 4, 2013. Accessed: April 7, 2017.
  9. Levine E. Classifications of Antiarrhythmic Agents. In: undefined, Classifications of Antiarrhythmic Agents. New York, NY: WebMD. http://emedicine.medscape.com/article/2172024-overview. Updated: August 6, 2014. Accessed: April 7, 2017.
  10. Blomström-Lundqvist C, Scheinman MM, Aliot EM, et al. ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias--executive summary. Circulation. 2003; 108 (15): p.1871-1909. doi: 10.1161/01.CIR.0000091380.04100.84 .
  11. Drugs.com. Adenosine. https://www.drugs.com/pro/adenosine.html. Updated: January 1, 2017. Accessed: April 7, 2017.
  12. Dave J. Torsade de Pointes. In: undefined, Torsade de Pointes. New York, NY: WebMD. http://emedicine.medscape.com/article/1950863-overview. Updated: February 1, 2017. Accessed: April 7, 2017.
  13. Zimetbaum PJ. Pathophysiology of the long QT syndrome. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/pathophysiology-of-the-long-qt-syndrome. Last updated: February 9, 2017. Accessed: April 7, 2017.
  14. UpToDate, Lexicomp, Inc. Magnesium sulfate: Drug information. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/magnesium-sulfate-drug-information. Last updated: April 7, 2017. Accessed: April 7, 2017.
  15. UpToDate. Flecainide: Drug information. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/flecainide-drug-information. Last updated: January 1, 2017. Accessed: October 10, 2017.
  16. UpToDate. Quinidine: Drug information. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/quinidine-drug-information. Last updated: January 1, 2017. Accessed: October 10, 2017.
  17. Le T, Bhushan V,‎ Sochat M, Chavda Y, Zureick A. First Aid for the USMLE Step 1 2018. New York, NY: McGraw-Hill Medical ; 2017
  18. Craig CR, Stitzel RE. Modern Pharmacology with Clinical Applications. Little, Brown Medical Division ; 1997
<div class="tooltip-content">null</div>