#MondayAnswer (but on Tuesday – happy July 4th!)

Great job to all who answered our Friday image challenge.

You were correct: the EKG presented was Second degree atrioventricular block: Mobitz type I (Wenckebach block) and no intervention necessary.

Definition: progressive prolongation of PR interval leading to a non-conducted P wave with the longest PR interval before the dropped beat and the shortest directly after the dropped beat.


Mechanism: reversible conduction block at the AV node level, AV node cells fatigue in a progressive manner.

Typically asymptomatic, rarely require intervention. WILL respond to atropine (as opposed to below the node mobitz 2 which might get worse with atropine)

Hints: consider when you appreciated “grouped beats” or several conducted beats in a row followed by a missed beat. Often p:QRS ratio of 3:2, 4:3, 5:4.

Tips: Carotid sinus massage (increases vagal tone) worsen Mobitz type I second degree AV block by slowing AV nodal conduction.  Improvement with carotid massage suggests that the conduction abnormality is below the level of the AV node, consistent with Mobitz type II second degree AV block

Final thoughts: at increased risk for further conduction system disease in future

Credit: Spencer Carter.

Email interesting imaging (CXR, CTs, EKGs, etc) w/ short explanation to utswecg@gmail.com


60 year old presents to ED with 6/10 chest pain and initial EKG shown below.