2nd Degree Heart Block

2nd Degree Heart Block

Shiken premium Upgrade Banner


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

Mobitz type 1: There is a noticeable delay in the AV conduction, which progressively increases until eventually an impulse is not conducted. On an ECG, this is reflected by an increase in the PR interval until a dropped beat is seen.

Mobitz type 2: This is characterised by intermittent failure of conduction in the atrial impulse to the ventricles, usually at a 2:1 ratio. Unlike Mobitz type 1, the PR interval will not lengthen.


Mobitz type 1 is often caused by an increase in vagal tone and typically occurs during the patient's sleep. Meanwhile, Mobitz type 2 is pathological in nature and has similar aetiology to first degree AV block.


The signs of Mobitz type 1 and 2 include bradycardia and hypotension.


Mobitz type 1 and 2 may be asymptomatic, but can also present with symptoms such as shortness of breath, chest pain, pre-syncope or syncope.


  • ECG: To assess the rhythm, a Holter monitor may be used.
  • Echo: If the LV function is impaired, the patient may benefit from cardiac resynchronisation therapy (CRT).


  • Stop any medications that may be causing the issue.
  • Depending on the severity of the condition, a temporary pacing wire may be required.
  • Mobitz type 2 will always require a permanent pacemaker.


Both Mobitz type 1 and 2 can progress to complete heart block. Prognosis after PPM implantation is typically good, although there can be complications such as death or injury from syncope.

Join Shiken For FREE

Gumbo Study Buddy

Explore More Subject Explanations

Try Shiken Premium
for Free

14-day free trial. Cancel anytime.
Get Started
Join 10,000+ learners worldwide.
The first 14 days are on us
96% of learners report x2 faster learning
Free hands-on onboarding & support
Cancel Anytime