Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

First degree atrioventricular block

William H Sauer, MD
Section Editor
Leonard I Ganz, MD, FHRS, FACC
Deputy Editor
Brian C Downey, MD, FACC


Atrioventricular (AV) block is defined as a delay or interruption in the transmission of an impulse from the atria to the ventricles due to an anatomic or functional impairment in the conduction system. The conduction disturbance can be transient or permanent, with conduction that is delayed, intermittent, or absent. Commonly used terminology includes:

First degree AV block – Delayed conduction from the atrium to the ventricle (defined as a prolonged PR interval of >200 milliseconds) without interruption in atrial to ventricular conduction.

Second degree AV block – Intermittent atrial conduction to the ventricle, often in a regular pattern (eg, 2:1, 3:2), or higher degrees of block, which are further classified into Mobitz type I (Wenckebach) and Mobitz type II second degree AV block.

Third degree (complete AV) block – No atrial impulses conduct to the ventricle.

High-grade AV block – Two or more consecutive blocked P waves.

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Nov 09, 2016.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Graybiel, A, McFarland, et al. Analysis of the electrocardiogram obtained from 1000 young healthy aviators. Am Heart J 1944; 27:524.
  2. Viitasalo MT, Kala R, Eisalo A. Ambulatory electrocardiographic recording in endurance athletes. Br Heart J 1982; 47:213.
  3. Josephson ME. Clinical Cardiac Electrophysiology: Techniques and Interpretations, 2d ed, Lea & Febiger, Philadelphia 1993.
  4. Barold SS. Indications for permanent cardiac pacing in first-degree AV block: class I, II, or III? Pacing Clin Electrophysiol 1996; 19:747.
  5. Ranganathan N, Dhurandhar R, Phillips JH, Wigle ED. His Bundle electrogram in bundle-branch block. Circulation 1972; 45:282.
  6. Rosen KM, Rahimtoola SH, Chuquimia R, et al. Electrophysiological significance of first degree atrioventricular block with intraventricular conduction disturbance. Circulation 1971; 43:491.
  7. Scheinman MM, Peters RW, Modin G, et al. Prognostic value of infranodal conduction time in patients with chronic bundle branch block. Circulation 1977; 56:240.
  8. Scheinman M, Brenman B. Clinical and anatomic implications of intraventricular conduction blocks in acute myocardial infarction. Circulation 1972; 46:753.
  9. Epstein AE, DiMarco JP, Ellenbogen KA, et al. 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. Circulation 2008; 117:e350.
  10. PACKARD JM, GRAETTINGER JS, GRAYBIEL A. Analysis of the electrocardiograms obtained from 1000 young healthy aviators; ten year follow-up. Circulation 1954; 10:384.
  11. Erikssen J, Otterstad JE. Natural course of a prolonged PR interval and the relation between PR and incidence of coronary heart disease. A 7-year follow-up study of 1832 apparently healthy men aged 40-59 years. Clin Cardiol 1984; 7:6.
  12. Cheng S, Keyes MJ, Larson MG, et al. Long-term outcomes in individuals with prolonged PR interval or first-degree atrioventricular block. JAMA 2009; 301:2571.
  13. Magnani JW, Wang N, Nelson KP, et al. Electrocardiographic PR interval and adverse outcomes in older adults: the Health, Aging, and Body Composition study. Circ Arrhythm Electrophysiol 2013; 6:84.
  14. Crisel RK, Farzaneh-Far R, Na B, Whooley MA. First-degree atrioventricular block is associated with heart failure and death in persons with stable coronary artery disease: data from the Heart and Soul Study. Eur Heart J 2011; 32:1875.
  15. Aro AL, Anttonen O, Kerola T, et al. Prognostic significance of prolonged PR interval in the general population. Eur Heart J 2014; 35:123.
  16. Holmqvist F, Hellkamp AS, Lee KL, et al. Adverse effects of first-degree AV-block in patients with sinus node dysfunction: data from the mode selection trial. Pacing Clin Electrophysiol 2014; 37:1111.
  17. Kwok CS, Rashid M, Beynon R, et al. Prolonged PR interval, first-degree heart block and adverse cardiovascular outcomes: a systematic review and meta-analysis. Heart 2016; 102:672.