2nd Degree Heart Block

2nd Degree Heart Block


Intermittent failure of atrial impulses to be conducted through AV node and His bundle, subdivided into Mobitz type 1 (Wenckebach) or Mobitz type 2

Mobitz type 1: delay in AV conduction progressively increases until an impulse is not conducted, on the ECG the PR interval gets longer and longer until there is a dropped beat

Mobitz type 2: intermittent failure of conduction of the atrial impulse to the ventricles usually in a 2:1 ratio, the PR interval does not lengthen


Mobitz type 1 can be due to increased vagal tone and often occurs during sleep

Mobitz type 2 is pathological and has a similar aetiology to 1st degree AV block  


Bradycardia, hypotension


Can be asymptomatic, SOB, chest pain, pre-syncope/syncope


ECG: To assess rhythm; may require a Holter monitor

Echo: if LV function impaired the patient may benefit from CRT


Stop offending medications

A temporary pacing wire may be required

Mobitz type 2 always requires a permanent pacemaker

Complications: Death, injuries from syncope


Both Mobitz type 1 and 2 can progress to complete heart block                        

Prognosis is good following PPM implantation

Death, injuries from syncope

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