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Second-Degree Atrioventricular Block Medication

  • Author: Ali A Sovari, MD, FACP; Chief Editor: Jeffrey N Rottman, MD  more...
 
Updated: Apr 28, 2014
 

Medication Summary

Atropine can be used for immediate treatment of symptomatic second-degree atrioventricular (AV) block in the atrioventricular node (AVN). For block in the His-Purkinje system, atropine does not improve conduction and can actually precipitate third-degree AV block by increasing the sinus rate and AVN conduction.

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Anticholinergic agents

Class Summary

Anticholinergic agents improve AV nodal conduction in second-degree block at the level of the AVN. Drug therapy in second-degree heart block is aimed at vagolysis; atropine is the only currently recommended agent.

Atropine IV/IM (AtroPen)

 

Atropine is used to increase heart rate through vagolytic effects, causing an increase in cardiac output. It enhances sinus node automaticity; in addition, it blocks the effects of acetylcholine at the AVN, thereby decreasing the refractory time and speeding conduction through the AVN. Insufficient doses of atropine can cause paradoxical effects, further slowing the heart rate.

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Contributor Information and Disclosures
Author

Ali A Sovari, MD, FACP Fellow in Clinical Cardiac Electrophysiology, Cedars Sinai Medical Center/Heart Institute

Ali A Sovari, MD, FACP is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Physician Scientists Association, American Physiological Society, Biophysical Society, Heart Rhythm Society, Society for Cardiovascular Magnetic Resonance

Disclosure: Nothing to disclose.

Coauthor(s)

Theodore J Gaeta, DO, MPH, FACEP Clinical Associate Professor, Department of Emergency Medicine, Weill Cornell Medical College; Vice Chairman and Program Director of Emergency Medicine Residency Program, Department of Emergency Medicine, New York Methodist Hospital; Academic Chair, Adjunct Professor, Department of Emergency Medicine, St George's University School of Medicine

Theodore J Gaeta, DO, MPH, FACEP is a member of the following medical societies: American College of Emergency Physicians, New York Academy of Medicine, Society for Academic Emergency Medicine, Council of Emergency Medicine Residency Directors, Clerkship Directors in Emergency Medicine, Alliance for Clinical Education

Disclosure: Nothing to disclose.

Abraham G Kocheril, MD, FACC, FACP, FHRS Professor of Medicine, University of Illinois College of Medicine

Abraham G Kocheril, MD, FACC, FACP, FHRS is a member of the following medical societies: American College of Cardiology, Central Society for Clinical and Translational Research, Heart Failure Society of America, Cardiac Electrophysiology Society, American College of Physicians, American Heart Association, American Medical Association, Illinois State Medical Society

Disclosure: Nothing to disclose.

Michael D Levine, MD Assistant Professor, Department of Emergency Medicine, Section of Medical Toxicology, Keck School of Medicine of the University of Southern California

Michael D Levine, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, American College of Medical Toxicology, American Medical Association, Phi Beta Kappa, Society for Academic Emergency Medicine, Emergency Medicine Residents' Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Brian Olshansky, MD Professor Emeritus of Medicine, Department of Internal Medicine, University of Iowa College of Medicine

Brian Olshansky, MD is a member of the following medical societies: American College of Cardiology, Heart Rhythm Society, Cardiac Electrophysiology Society, American Heart Association

Disclosure: Received honoraria from Guidant/Boston Scientific for speaking and teaching; Received honoraria from Medtronic for speaking and teaching; Received consulting fee from Guidant/Boston Scientific for consulting; Received consulting fee from BioControl for consulting; Received consulting fee from Boehringer Ingelheim for consulting; Received consulting fee from Amarin for review panel membership; Received consulting fee from sanofi aventis for review panel membership.

Chief Editor

Jeffrey N Rottman, MD Professor of Medicine, Department of Medicine, Division of Cardiovascular Medicine, University of Maryland School of Medicine; Cardiologist/Electrophysiologist, University of Maryland Medical System and VA Maryland Health Care System

Jeffrey N Rottman, MD is a member of the following medical societies: American Heart Association, Heart Rhythm Society

Disclosure: Nothing to disclose.

Additional Contributors

Eddy S Lang, MDCM, CCFP(EM), CSPQ Associate Professor, Senior Researcher, Division of Emergency Medicine, Department of Family Medicine, University of Calgary Faculty of Medicine; Assistant Professor, Department of Family Medicine, McGill University Faculty of Medicine, Canada

Eddy S Lang, MDCM, CCFP(EM), CSPQ is a member of the following medical societies: American College of Emergency Physicians, Society for Academic Emergency Medicine, Canadian Association of Emergency Physicians

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors Ryan L Cooley, MD, and Raluca B Arimie, MD to the development and writing of the source article.

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Typical Mobitz I atrioventricular block with progressive prolongation of PR interval before blocked P wave. Pauses are always less than sum of 2 preceding beats because PR interval after pause always shortens.
Mobitz II atrioventricular (AV) block with intermittent periods of 2:1 AV block. If only 2:1 block was seen in beginning of strip, site of block could not be localized with certainty; however, single dropped QRS complex at end of strip with constant PR interval indicates that this block is localized in one of the bundle branches.
Variable-ratio Mobitz I atrioventricular block. Note marked PR-interval prolongation in first beat of each cycle. Maximum prolongation of PR interval takes place in second beat of cycle, with much smaller increments in subsequent beats. Also, notice that R-R interval actually shortens with each beat—paradox of shortening R-R interval when PR interval increases by diminishing increments.
Sinus rhythm with Mobitz I second-degree 3:2 infranodal atrioventricular (AV) block and bifascicular block. Note that AH interval (indicative of AV nodal conduction) remains constant. HV interval (indicative of His-Purkinje conduction) increases from 65 msec (after first P wave) to 185 msec (after second P wave). Third P wave is followed a His bundle deflection (H) but no QRS complex. AV block occurs in His-Purkinje system below site of recording of His bundle potential. Note shorter PR interval after nonconducted P wave, typical of Mobitz I AV block. HRA = high right atrial electrogram; A = atrial deflection; HB = His bundle electrogram, proximal and distal; H = His bundle deflection; RV = right ventricular electrogram; T = time line, 50 msec.
Representative 12-lead electrocardiogram in asymptomatic 78-year-old woman during recent noncardiac surgery. Patient was referred for implantation of permanent pacemaker with diagnosis of sinus tachycardia with 2:1 atrioventricular (AV) block and narrow QRS complex. As sinus rate slowed, 1:1 AV conduction resumed. Intracardiac recordings confirmed diagnosis of infra-Hisian 2:1 AV block.
Electrocardiogram of patient with Mobitz I (Wenckebach) second-degree atrioventricular block.
Electrocardiogram of patient with Mobitz II second-degree atrioventricular block.
 
 
 
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