Mobitz, Wenckebach, and Hay AV Blocks


Other Known AliasesSecond degree AV blocks


DefinitionSecond degree AV block refers to the inability of the P-wave to initiate a QRS complex.  In Type I (Wenckebach), there is progressive elongation of the PR interval until a beat is dropped.

Image result for mobitz type I

In Type II (Hay), there is no progressive elongation, but there are dropped beats.

Image result for mobitz type II


Clinical SignificanceMobitz Type I is generally considered a benign entity due to absence of structural changes on histology.  Mobitz Type II is concerning because it can progress to a complete heart block with sudden cardiac arrest.


History – Named after Woldemar Mobitz (1889-1951), who was a Russian-German physician and earned his doctorate of medicine in 1914 from the Universities of Freiburg and Munich.  He researched heart block extensively in the early 1900’s which culminated in his landmark paper in 1924, where he classified the two distinct types of second degree heart block. 

Woldemar Mobitz The Apical View The Journey Continues To the end of the

Woldemar Mobitz


Interestingly, these two types were already described by:

1) Karel Frederik Wenckebach (1864-1940), who was a Dutch physician and anatomist in Hague and recieved his medical doctorate from the University of Groningen.  He published his findings of a irregular pulses due to partial blockage of the AV conduction system causing progressive lengthening of conduction time in cardiac tissue in 1899.


2) John Hay (1873-1959), who was an English physician and received his medical doctorate from Victoria University of Manchester in 1901.  He first described what would become Type II AV block in 1905 in a 65yo man with a 2.5 year history of dyspnea on exertion.  Interestingly, he did this without the benefit of elctrocardiography.


  1. Firkin BG and Whitwirth JA.  Dictionary of Medical Eponyms. 2nd ed.  New York, NY; Parthenon Publishing Group. 1996.
  2. Bartolucci S, Forbis P.  Stedman’s Medical Eponyms.  2nd ed.  Baltimore, MD; LWW.  2005.
  3. Yee AJ, Pfiffner P. (2012).  Medical Eponyms (Version 1.4.2) [Mobile Application Software].  Retrieved http://itunes.apple.com.
  4. Whonamedit – dictionary of medical eponyms. http://www.whonamedit.com
  5. Silverman ME, Upshaw CB, Lange HW. Woldemar Mobitz and His 1924 classification of second-degree atrioventricular block. Circulation. 2004; 110(9):1162-7. [pubmed]
  6. Mobitz W. Über die unvollständige Störung der Erregungsüberleitung zwischen Vorhof und Kammer des menschlichen Herzens. Zeitschrift für die Gesamte Experimentelle Medizin, Berlin 1924, 41: 180–23.
  7. Wenckebach KF. De Analyse van den onregelmatigen Pols. II. Over eenige Vormen van Allorhythmie en Bradycardie. Nederl Tijdschr Geneesk 1899;35:665.
  8. Hay J. Bradycardia and cardiac arrhythmia produced by depression of certain of the functions of the heart. The Lancet 1906, 1: 139–143
  9. Upshaw CB, Silverman ME.  John Hay: Discoverer of Type II Atrioventricular Block.  Clin Cardiol.  2000;23:869-871

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