Summary of Heart Blocks

1st Degree Heart Block:

 • Prolonged PR >200ms (5 small squares).

 • Narrow & regular rhythm.

 • No Treatment

2nd Degree, Mobitz I Heart Block (aka Wenckebach): 

 • Prolonged PR then Dropped P

 • Progressive prolongation of PR culminating in non-conducted P wave. PR longest before dropped beat. PR shorted after dropped beat. Narrow & irregular rhythm.

 • No Sx? No Treatment. Sx? Brady Management.

2nd Degree, Mobitz II HeartBlock:

 • Dropped P without PR prolongation

 • Non-conducted P waves without "warning" of PR prolongation.

 • PR intervals in conducted beats constant. QRS often wide.

 • May be no pattern or fixed relationship (2:1 or 3:1 block)

 • Treatment: Pacemaker

3rd Degree, Complete Heart Block: 

 • No association between P and QRS

 • Atrial rate > Ventricular Rate. Regular ventricular rate.

 • Block in AV node: Junctional escape (40-60), narrow QRS

 • Block infranodal level: Ventricular escape (20-40), wide QRS

 • Treatment: Pacemaker - Will not respond to atropine if wide QRS (block beyond AV node)



- Dr. Sarah Foohey @SarahFoohey



#HeartBlocks #Types #Classification #degrees #summary #Diagnosis #EKG #electrocardiogram #ecg #cardiology