Second-degree AV Block, Mobitz Type I (Wenckebach)

Creado por team@ekgdx.com el 15 de Diciembre de 2023

Let’s talk about second-degree AV block, Mobitz type I (Wenckebach).

Second-degree AV block, Mobitz type I (Wenckebach) is characterized by progressive prolongation of the PR intervals until the P wave is blocked resulting into a pause. 

Criteria

  • Progressive prolongation of the PR interval until a P wave is blocked.
  • PP interval is usually regular or constant.
  • RR interval containing the blocked P wave is less than twice the preceding PP interval.

NOTE: Mobitz type I is the most common type of second-degree AV block.

NOTE: Occasionally, patients can be asymptomatic and may not require immediate treatment.  

NOTE: Wenckebach phenomenon may occur in any segment of the conducting system and is not necessarily confined to the AV node.

NOTE: We have a section of EKG Challenges in the Volume II of EKGDX. In this video you can see a wonderful case long AV Wenckebach cycles from that collection of EKGs. 

Posible causes: Inferior MI, Increased vagal tone, following cardiac surgery, Drugs (beta-blockers, calcium channel blockers, digoxin, amiodarone, etc), others.

 

Graphic explanation

 

Note the progressive prolongation of the PR interval until a P wave is blocked. 

 

A classic example in a 12-lead EKG.

 

An EKG Challenge from our Vol II. Click in the EKG to see the analysis. 

 

Karel Frederik Wenckebach

History

In 1873, Luigi Luciani (1840 – 1919) was an italian neuroscientist who demonstrated the cardiac group beating and recorded 2nd degree AV blocks in frog hearts at Carl Ludwig’s laboratory in Leipzig. Wenckebach later credited Luciani with this discovery referring to the phenomena as ‘Luciani periods‘. It is currently known as ‘Wenckebach periodicity'.

Alfred Lewis Galabin (1843 – 1913) was an English obstetric physician. He was the first person to document atrioventricular block in humans using an apexcardiogram in 1873 and published in 1875 . He performed his studies while working as a house officer at Guy’s Hospital, London, UK. His patient was 34 years old, experienced attacks of near syncope, and had a pulse rate that varied between 25 and 30 beats/min.

In 1899, the dutch physician and anatomist Karel Frederik Wenckebach (1864 – 1940) demonstrated impairment of AV conduction leading to progressive lengthening and blockage of AV conduction in frogs. The condition was referred to as "second degree AV block" and later named "Wenckebach phenomenon" and reclassified as Mobitz type I block in Mobitz's 1924 paper.

In 1905, John Hay (1873 – 1959) was an English physician who was the first to record a form of second degree atrioventricular (AV) block that is now better known as Mobitz type II. He recorded simultaneous jugular venous and radial arterial pulses of a 65-year-old man with a heart rate of 80 bpm that suddenly decreased to 40 bpm. His paper was published in 1906 (Lancet, Volume 167, Issue 4299, 20 January 1906, Pages 139-143).

In 1924, Woldemar Mobitz (1889 – 1951) was a German physician who classified second-degree atrioventricular (AV) block into 2 principle types, subsequently referred to as Mobitz type I (Wenckebach) and Mobitz type II (Hay), in his paper: "Mobitz, W. Über die unvollständige Störung der Erregungs-überleitung zwischen Vorhof und Kammer des menschlichen Herzens. Z. Ges. Exp. Med. 41, 180–237 (1924)".

Do you want to practice with complex EKGs?

If you are a cardiology fellow who needs to practice for the ABIM cardiology board or you are someone who wants to practice with complex 12-lead EKGs, our Volume II is what you need.

Do you want to improve your EKG skills?

With our unique, revolutionary and innovative educational platform, you will learn EKG easier than ever. Download the App here and get started. I hope you enjoy our interactive way of learning EKG. 

References

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Dr. Roig

Second-degree AV Block Mobitz Type I (Wenckebach)