Bradycardia

Question 1

Major AV Blocks:

Complete or 3rd degree is the most clinically significant block because it is most likely to cause cardiovascular collapse & require immediate pacing.

Question 2

Major AV Blocks:

2nd Degree AV Block blocks some but not all atrial impulses before they reach the ventricles. The 2nd Degree AV Block can be further classified as Mobitz Type1 or Mobitz Type 2

Answer 2

Mobitz Type 1 AV Block:
-Also known as Wenckebach, typically occurs at the AV node.
-Mobitz Type 1 is characterized by successive prolongation of the PRI until an atrial impulse is not conducted to the ventricles.

Mobitz Type 2 AV Block
-Occurs below the level of the AV node.
-Mobitz Type 2 is characterized by intermittent, non conduction of P waves (atrial impulses to the ventricle” w/ a constant PRI or conducted beats.
-There can be a consistent ration of atrial to ventricular depolarizations.

Question 3

Major AV Blocks:

3rd Degree AV or Complete Heart Block

Answer 3

3rd Degree or Complete Heart Block
-Atrial impulses are not conducted through to the Ventricles
-Atria and ventricles beat independently of each other

Question 4

What 3 criteria are present when Unstable Bradycardia exists clinically?

Answer 4

1. The HR is slow
2. The pt has symptoms
3. The symptoms are due to the slow HR:
   *Hypotension
   *Acute AMS
   *S/O Shock
   *Ischemic chest discomfort
   *Acute heart failure

Question 5

**Bradycardia can be a s/o life-threatening Hypoxia

**Bradycardia associated w/ Hypertension can be a s/o a life-threatening increase in ICP especially in the setting of stroke or Brain injury.

Question 6

Treatment for Symptomatic Bradycardia:

Answer 6

-Unless you find other immediately reversible underlying causes, Atropine remains the 1st line drug for Acute Unstable Bradycardia. Given Atropine 1 mg Q3-5 minutes to a max of 3 mg.
-Atropine works by reversing cholinergic-mediated decreases in HR and AV node conduction.
-Dopamine & Epinephrine my be successful as an alternative to TCP.

Question 7

Atropine

Answer 7

-Use Atropine cautiously in the presence of acute coronary ischemia or MI. An Atropine mediated increase in HR may worsen ischemia or increase infarct size.
-DO NOT RELY ON ATROPINE TO TREAT
-2ND DEGREE MOBITZ TYPE 2
-3RD DEGREE COMPLETE HEART BLOCK OR PTS W/ 3RD DEGREE HEART BLOCK W/ A NEW WIDE QRS COMPLEX.
-HEART TRANSPLANT PTS
These bradycardias will likely not respond to reversal of cholinergic effects of Atropine.

Question 8

Critical Concept for Bradycardia:

The key clinical question is whether the bradycardia is causing the pt’s Sox or some other illness is causing the bradycardia?

Answer 8

Ex: Hypotension associated w/ bradycardia may be due to myocardial dysfunction rather than the bradycardia.