AV Blocks

Question 1

Big picture, how do we define an AV block?

Answer 1

A block that causes a disruption of Atrial to Ventricular conduction.

Question 2

What exactly is a first degree AV block and what is the time?

Answer 2

Prolonged AV node conduction . Greater than 0.2 seconds.

Question 3

What is key to defining a first degree AV block?

Answer 3

The PR interval is consistently prolonged. It is prolonged, but the same amount in each cycle.

Question 4

4 common causes of first degree AV block?

Answer 4

Atherosclerosis, HTN, Diabetes and fibrosis.

Question 5

Explain second degree type 1 block?

Answer 5

Each progressive AV conduction is longer and longer until one doesn’t get through. So, PR interval is longer and longer until you lose a QRS.

Question 6

7 causes of Mobile type 1?

Answer 6

Atherosclerosis, HTN, Diabetes, Fibrosis, AMI-inferior, Digitalis toxicity, and myocarditis.

Question 7

Where is the block in the heart with type 1 and what does the QRS look like?

Answer 7

The block is at the AV node. Super narrow QRS.

Question 8

Explain what is going on with a mobitz type 2?

Answer 8

No prior PR lengthening, you just randomly drop a QRS. One of the impulses does not get through and you have a high Atrial to Ventricular ratio. Could be 2:1, 3:1, or higher.

Question 9

What where is the block happening for type 2. What kind of MI is it associated with? What is a common cause of Type 2.

Answer 9

Distal to the AV node, so bundle of His or bundle branches. Anterior MI. IHD.

Question 10

What is an important distinction of the P wave in type 2?

Answer 10

The P wave is on time and never premature.

Question 11

Explain the dynamic of the location of a complete heart block and how that affects rhythm?

Answer 11

If it is above the AV node then the AV junction can take over pacing for the ventricles which would be about 40-55. If the block is below the AV node then the ventricles will need to pace themselves and it will be about 20-40.

Question 12

What are we looking for in the EKG for a complete heart block?

Answer 12

AV dissociation. The atria are pacing themselves but that impulse is never getting through so the ventricles need to pace themselves. Two independent pacings are going on.

Question 13

2 common causes of Complete heart block?

Answer 13

IHD and cardiac surgery

Question 14

What do we see on EKG that indicates the ventricles are pacing themselves?

Answer 14

Large, wide PVC like complexes.

Question 15

How do we treat a third degree AV block?

Answer 15

Pacemaker