AV Heart Blocks

Question 1

Different Types of AV Heart Blocks

Answer 1

• First-degree AV Block
• Second-degree AV block, Type 1- Mobitz 1
• Second-degree AV block, Type II- Mobitz 2
• Third-degree AV block

Question 2

Identifying Heart Blocks

Answer 2

• PR interval is key to identify the type
• the width of the QRS and the ventricular rate are key to identify location of the block
• the wider and slower the QRS, the lower the block

Question 3

First-degree AV Block

Answer 3

• Regular: (R-R interval)
• Rate: 60-100 bpm, can be slower/faster
• P waves: normal in size, shape, direction; 1 P wave for every QRS complex
• PR interval: >0.20 seconds and constant
• QRS complex: 0.10 seconds or >0.10 seconds (wide)
• QT interval:: 0.36-0.44 seconds

> constant, prolonged PR interval (> 0.20. seconds)

Question 4

Interventions for First-Degree AV block

Answer 4

• assess patient

- check medications for possible cause

Question 5

Second-degree AV block Type 1, Mobitz 1 (Wenckebach)

Answer 5

“wenckebach”

• progressive increase in the length of the PR interval until there is a P wave w/ no QRS (dropped beat)
• “long, longer, drop”
• Ventricular rate: irregular (R-R), b/c QRS is dropped
• Atrial rate: regular (P-P)
• P waves: normal in size, shape, and direction, but more P’s than QRS’s
• PR interval: NOT constant
• QRS complex: 0.10 seconds (wide)
• QT interval: 0.36-0.44 seconds

Question 6

Interventions for Second-degree AV Heart Block Type I, Mobitz 1

Answer 6

> Stable:

• notify MD if new for pt
• assess pt
• check medication for possible cause

> Unstable:

• call a RR or get provider to bedside
• identify and treat possible causes
• Atropine 1mg. Repeat every 3-5 min. Max: 3 mg
• TCP (transcutaneous pacemaker)
• PPM (permanent pacemaker)
• Dopamine 2-20 mcg/kg/min
• Epinephrine 2-10 mcg/kg/min

Question 7

Second-degree AV block, Mobitz Type II

Answer 7

• Ventricular rate: irregular
• Atrial rate: regular (the P’s plot out)
• Atrial rate is greater than ventricular rate
• P waves: normal in size, shape, and direction, but more P’s than QRS’s; not every P is followed by a QRS
• PR interval: can be normal or prolonged, but it is constant
• QRS complex: 0.10 seconds if block occurs below bundle of HIS
• QT interval: 0.36-0.44

-the QRS drops but the PR interval is the same

Question 8

Interventions for Second-degree Heart Block Type II, Mobitz 2

Answer 8

• Assess patient
• Symptomatic; call RR, get MD to bedside
• prepare for pacemaker
• review medications for possible cause

Question 9

Third-degree AV Heart Block

Answer 9

ventricular and atrial rate are regular, but there is no relationship between upper and lower part of the heart

• Atrial rate greater than ventricular rate
• P waves: normal in size, shape, and direction, but more P’s than QRS’s
• PR interval: none, no true PR interval
• QRS complex: 0.10 seconds
• QT interval: 0.36-0.44 seconds

Question 10

Second-degree Type 1 VS Second-degree Type 2

Answer 10

Type 1: the PR interval gets progressively longer and then a QRS drops
Type 2: the PR interval stays constant and then a QRS drops

Question 11

Interventions for Third-degree AV Heart Block

Answer 11

• call a RR if new onset
• emergent transcutaneous pacing and prepare for permanent pacemaker
• dopamine or epinephrine IV to treat symptoms