Second degree AV block historical perspective

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

Second-degree AV block was first described as a progressive delay between the atrial and ventricular contraction by Dr. Wenckebach in 1899. Dr. Mobitz then divided the second-degree AV block into two subtypes. In 1905, Dr. Hay figured out the pause following a wave was due to the failure of ventricular muscles to respond to a stimulus.

• In 1899, Dr. Wenckebach described progressive delay between atrial and ventricular contraction and the eventual failure of a P wave to reach the ventricles.
• Dr. Mobitz then divided the second-degree AV block into two subtypes.
• In 1905, Dr. John Hay discovered the second degree of AV block.^[1]
• Dr. Hay was examining a patient who complains of slow pulse and dyspnea on exertion for more than 2 years. Dr. Hay noticed the heart rate dropping from 80 beats to 40 beats per minute.
• Dr. Hay noted the a waves and the arterial pulse to remain stable in the beginning. However, recording pulsation several times resulted in “a” waves that were not followed by c wave. The a-c jugular wave interval was used as a measurement of AV conduction.
• Dr. Hay figured out that the pause following a wave was due to the failure of ventricular muscles to respond to a stimulus.

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