3rd Degree AV Block

Question 1

What is another name for 3rd degree AV block?

Answer 1

Complete heart block.

Question 2

What happens to the atrial and ventricular activity in 3rd degree AV block?

Answer 2

P waves and QRS complexes are independent (AV dissociation).

Question 3

How do P waves appear in 3rd degree AV block?

Answer 3

Regular, but not related to QRS complexes.

Question 4

How do QRS complexes appear in 3rd degree AV block?

Answer 4

Regular but independent of P waves; can be narrow or wide depending on escape focus.

Question 5

What is the typical ventricular rate in complete heart block?

Answer 5

Slow, often <40 bpm (junctional or ventricular escape rhythm).

Question 6

Why does 3rd degree AV block occur?

Answer 6

The electrical signal from the atria does not conduct to the ventricles.

Question 7

What are the main ECG characteristics of 3rd degree AV block?

Answer 7

Regular P waves, regular QRS, no relation between them (AV dissociation).

Question 8

What is the clinical significance of 3rd degree AV block?

Answer 8

It is the most severe AV block and can cause syncope, low cardiac output, or sudden death.

Question 9

What are 3 congenital or structural causes of complete heart block?

Answer 9

Congenital AV block, severe heart disease, myocardial infarction.

Question 10

What medication is classically associated with worsening AV block?

Answer 10

Digoxin (as well as beta-blockers and calcium channel blockers).

Question 11

What symptoms suggest low cardiac output in complete heart block?

Answer 11

Weak pulse, mental status changes, pale/clammy skin, syncope.

Question 12

First step if a patient is unstable with 3rd degree AV block?

Answer 12

Activate the emergency response system (resuscitation).

Question 13

What drug can be trialed to increase heart rate in symptomatic complete heart block?

Answer 13

Atropine (though often ineffective in complete block).

Question 14

What is the definitive long-term treatment for 3rd degree AV block?

Answer 14

Permanent pacemaker.

Question 15

What temporary measures can be used while awaiting pacing in unstable patients?

Answer 15

Temporary pacing (transcutaneous or transvenous) and supportive care.