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.

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)

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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.

Questions

Strasberg B, Amat-Y-Leon F, Dhingra RC, et al. Natural history of chronic second-degree atrioventricular nodal block. Circulation. 1981 May. 63(5):1043-9. [QxMD MEDLINE Link]. [Full Text].
[Guideline] Gregoratos G, Abrams J, Epstein AE, et al for the American College of Cardiology/American Heart Association Task Force on Practice Guidelines/North American Society for Pacing and Electrophysiology Committee to Update the 1998 Pacemaker Guidelines. ACC/AHA/NASPE 2002 guideline update for implantation of cardiac pacemakers and antiarrhythmia devices: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/NASPE Committee to Update the 1998 Pacemaker Guidelines). Circulation. 2002 Oct 15. 106(16):2145-61. [QxMD MEDLINE Link]. [Full Text].
[Guideline] Epstein AE, DiMarco JP, Ellenbogen KA, et al, for the Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices) developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. J Am Coll Cardiol. 2008 May 27. 51(21):e1-62. [QxMD MEDLINE Link]. [Full Text].
Barold SS, Herweg B. Second-degree atrioventricular block revisited. Herzschrittmacherther Elektrophysiol. 2012 Dec. 23(4):296-304. [QxMD MEDLINE Link].
Barold SS, Hayes DL. Second-degree atrioventricular block: a reappraisal. Mayo Clin Proc. 2001 Jan. 76(1):44-57. [QxMD MEDLINE Link]. [Full Text].
Silverman ME, Upshaw CB Jr, Lange HW. Woldemar Mobitz and His 1924 classification of second-degree atrioventricular block. Circulation. 2004 Aug 31. 110(9):1162-7. [QxMD MEDLINE Link]. [Full Text].
Zehendet M, Meinertz T, Keul J, Just H. ECG variants and cardiac arrthymias in athletes: clinical relevance and prognostic importance. Am heart J. 1990 Jun. 119(6):1378-91. [QxMD MEDLINE Link].
Doutreleau S, Pistea C, Lonsdorfer E, Charloux A. Exercise-induced second-degree atrioventricular block in endurance athletes. Med Sci Sports Exerc. 2013 Mar. 45(3):411-4. [QxMD MEDLINE Link]. [Full Text].
Cho SW, Kang YJ, Kim TH, et al. Primary cardiac lymphoma presenting with atrioventricular block. Korean Circ J. 2010 Feb. 40(2):94-8. [QxMD MEDLINE Link]. [Full Text].
Antoniou T, Gough KA. Early-onset pentamidine-associated second-degree heart block and sinus bradycardia: case report and review of the literature. Pharmacotherapy. 2005 Jun. 25(6):899-903. [QxMD MEDLINE Link].
[Guideline] Neumar RW, Otto CW, Link MS, et al. Part 8: adult advanced cardiovascular life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010 Nov 2. 122(18 Suppl 3):S729-67. [QxMD MEDLINE Link]. [Full Text].
Sacca F, Puorro G, Marsili A, et al. Mobitz type I and II atrioventricular blocks during fingolimod therapy. Neurol Sci. 2016 Sep. 37(9):1557-9. [QxMD MEDLINE Link].
Limmroth V, Ziemssen T, Lang M, et al. Electrocardiographic assessments and cardiac events after fingolimod first dose - a comprehensive monitoring study. BMC Neurol. 2017 Jan 18. 17(1):11. [QxMD MEDLINE Link]. [Full Text].
Makaryus JN, Catanzaro JN, Friedman ML, Katoma KC, Makaryus AN. Persistent second-degree atrioventricular block following adenosine infusion for nuclear stress testing. J Cardiovasc Med. 2008 Mar. 9(3):304-7. [QxMD MEDLINE Link].
Belem L de S, Inacio CA. Second degree atrioventricular block Mobitz type I after administration of benzathine penicillin: case report. Rev Bras Anestesiol. 2009 Mar-Apr. 59(2):219-22. [QxMD MEDLINE Link].
Haddad FA, Nadelman RB. Lyme disease and the heart. Front Biosci. 2003 Sep 1. 8:s769-82. [QxMD MEDLINE Link].
Del Valle I, Hoang V, Wood ST. A case of Lyme carditis with variable heart block successfully treated with oral doxycycline. Cureus. 2022 May. 14(5):e24729. [QxMD MEDLINE Link]. [Full Text].
Van Herendael B, Van Herendael H, De Raedt H. Second-degree atrioventricular block as the first sign of sarcoidosis in a previously asymptomatic patient. Acta Cardiol. 2007 Jun. 62(3):299-301. [QxMD MEDLINE Link].
Lev M. Anatomic basis for atrioventricular block. Am J Med. 1964 Nov. 37:742-8. [QxMD MEDLINE Link].
Hsu YJ, Lin YF, Chau T, et al. Electrocardiographic manifestations in patients with thyrotoxic periodic paralysis. Am J Med Sci. 2003 Sep. 326(3):128-32. [QxMD MEDLINE Link].
Vinsonneau U, Delluc A, Bergez C, Caumes D, Talarmin F. [Second degree atrioventricular block in mixed connective tissue disease]. Rev Med Interne. 2005 Aug. 26(8):656-60. [QxMD MEDLINE Link].
den Dulk K, Brugada P, Braat S, Heddle B, Wellens HJ. Myocardial bridging as a cause of paroxysmal atrioventricular block. J Am Coll Cardiol. 1983 Mar. 1(3):965-9. [QxMD MEDLINE Link]. [Full Text].
Lin SM, Hwang HK, Chen MR. Amplatzer septal occluder-induced transient complete atrioventricular block. J Formos Med Assoc. 2007 Dec. 106(12):1052-6. [QxMD MEDLINE Link]. [Full Text].
Thanopoulos BD, Rigby ML. Outcome of transcatheter closure of muscular ventricular septal defects with the Amplatzer ventricular septal defect occluder. Heart. 2005 Apr. 91(4):513-6. [QxMD MEDLINE Link]. [Full Text].
Arias MA, Sanchez AM. Obstructive sleep apnea and its relationship to cardiac arrhythmias. J Cardiovasc Electrophysiol. 2007 Sep. 18(9):1006-14. [QxMD MEDLINE Link].
Erkapic D, Kim WK, Weber M, et al. Electrocardiographic and further predictors for permanent pacemaker requirement after transcatheter aortic valve implantation. Europace. 2010 Aug. 12(8):1188-90. [QxMD MEDLINE Link]. [Full Text].
Nardi P, Pellegrino A, Scafuri A, et al. Permanent pacemaker implantation after isolated aortic valve replacement: incidence, risk factors and surgical technical aspects. J Cardiovasc Med (Hagerstown). 2010 Jan. 11(1):14-9. [QxMD MEDLINE Link].
Bastani H, Insulander P, Schwieler J, et al. Cryoablation of superoparaseptal and septal accessory pathways: a single centre experience. Europace. 2010 Jul. 12(7):972-7. [QxMD MEDLINE Link].
Sovari AA, Bodine CK, Farokhi F. Cardiovascular manifestations of myotonic dystrophy-1. Cardiol Rev. 2007 Jul-Aug. 15(4):191-4. [QxMD MEDLINE Link].
Brvar M, Bunc M. High-degree atrioventricular block in acute ethanol poisoning: a case report. Cases J. 2009 Sep 9. 2:8559. [QxMD MEDLINE Link]. [Full Text].
Mangi MA, Jones WM, Mansour MK, Napier L. Atrioventricular block second-degree. StatPearls [Internet]. 2021 Aug 29. [QxMD MEDLINE Link]. [Full Text].
Cevik BS, Cevik A, Tavli E. Second degree heart block associated with QT prolongation. Indian Pacing Electrophysiol J. 2010 Feb 1. 10(2):96-8. [QxMD MEDLINE Link]. [Full Text].
Zehender M, Meinertz T, Keul J, Just H. ECG variants and cardiac arrhythmias in athletes: clinical relevance and prognostic importance. Am Heart J. 1990 Jun. 119(6):1378-91. [QxMD MEDLINE Link].
Takaoka H, Funabashi N, Ozawa K, et al. Computed tomography is important in appropriately diagnosing patients with third-degree atrioventricular block and second-degree atrioventricular block but not Wenckebach type. Int J Cardiol. 2017 Feb 1. 228:700-6. [QxMD MEDLINE Link].
[Guideline] 2005 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Part 7.3: Management of symptomatic bradycardia and tachycardia. Circulation. 2005 Nov 28. 112(suppl IV):IV-67-IV-77. [Full Text].
Aste M, Oddone D, Donateo P, et al. Syncope in patients paced for atrioventricular block. Europace. 2016 Nov. 18(11):1735-9. [QxMD MEDLINE Link].
Sahin Yildiz B, Astarcioglu MA, Baskurt Aladag N, et al. The frequency of type 2 second-degree and third-degree atrioventricular block induced by blunt chest trauma in the emergency department: A multicenter study. Ulus Travma Acil Cerrahi Derg. 2015 May. 21(3):193-6. [QxMD MEDLINE Link]. [Full Text].

Media Gallery

Second-Degree Atrioventricular Block. 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.
Second-Degree Atrioventricular Block. 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.
Second-Degree Atrioventricular Block. 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.
Second-Degree Atrioventricular Block. 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.
Second-Degree Atrioventricular Block. 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.
Second-Degree Atrioventricular Block. Electrocardiogram of patient with Mobitz I (Wenckebach) second-degree atrioventricular block.
Second-Degree Atrioventricular Block. Electrocardiogram of patient with Mobitz II second-degree atrioventricular block.

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Author

Ali A Sovari, MD, FACP, FACC Attending Physician, Cardiac Electrophysiologist, Cedars Sinai Medical Center and St John's Regional Medical Center

Ali A Sovari, MD, FACP, FACC 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 Residency Directors in Emergency Medicine, 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, FESC, FAHA, FACC, FHRS Professor Emeritus of Medicine, Department of Internal Medicine, University of Iowa College of Medicine

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

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Astra Zeneca, Artivion<br/>DSMB.

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.