Second-degree AV Block, Mobitz Type II
Let’s talk about Second-degree AV block, Mobitz type II
Second-degree AV block, Mobitz type II is characterized by intermittent non-conducted P waves without progressive prolongation of the PR interval.
Criteria
- PR interval constant.
- QRS usually wide in the majority of cases.
- Atrial rate regular or constant.
- PR interval before and after the blocked P wave is constant.
- The RR interval containing the blocked P wave is an exact multiple (2x, 3x, etc) of the preceding RR interval.
Possible causes: Infiltrative myocardial disease (Amyloidosis, Haemochromatosis, Sarcoidosis), Lenegre’s disease, MI, Hyperkalemia, Drugs (beta-blockers, calcium channel blockers, digoxin, amiodarone, lidocaine, etc.), others.
Graphic explanation of a second-degree AV block, Mobitz type II.
John Hay (1873 – 1959) was the first to record this form of second degree atrioventricular (AV) block. Image credit from Br Heart J. 1959 Oct; 21(4): 573–577.
Screenshot of the diagram. Click in the image to open the paper.
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 anatamist 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)".
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