Mobitz, Wenckebach, and Hay AV Blocks
Other Known Aliases – Second degree AV blocks
Definition – Second 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.
In Type II (Hay), there is no progressive elongation, but there are dropped beats.
Clinical Significance – Mobitz 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.
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.
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- 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.
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