Heart block

Question 1

ECG in different heart blocks

Answer 1

1st deg - Prolonged PR interval

2nd deg -
●Mobitz type 1: gradually increasing PR interval until a drop beat
●Mobitz type 2: PR interval no change, drop beat+

3rd deg-
No relation to P and QRS waves
Regular QRS

Question 2

Mx of 1st deg and mobitz type 1 heart block

Answer 2

1. Stop offending drug
2. Asymptomatic - no rx
3. Symptomatic - ATROPINE

Question 3

Mx of mobitz type 2 heart block

Answer 3

1. Stop offending drug
2. PACEMAKER even if asymptomatic

ATROPINE WILL PPT 3rd deg heart block

Question 4

Mx of 3rd deg heart block

Answer 4

Dobutamine
Atropine
PACEMAKER

Question 5

Where is the block in different heart blocks

Answer 5

AV node, bundle of HIS

Question 6

Causes of heart block

Answer 6

1. MI, mainly-
   Rt coronary artery gives branch to AV node, shown as inferior wall MI on ECG (2,3,aVF leads)
2. Hyperkalemia
3. Drugs - BB, CCB, adenosine, amiodarone, digoxin
4. Lyme disease - 3rd deg AV block
5. Neonatal lupus - congenital AV block (d/t maternal anti ro/la antibodies)
6. Normal in athletes

Question 7

ECG in RBBB and LBBB

Answer 7

RBBB-
V1-V3: M pattern on QRS (dominant S wave)
V5-V6, 1, aVL: W pattern

LBBB-
V1-V3: W pattern on QRS
V5-V6, 1, aVL: M pattern

Question 8

*Causes of LBBB

Answer 8

1. Anterior MI
2. Aortic stenosis
3. Ischemic Heart disease
4. Dilated cardiomyopathy
5. Digoxin toxicity
6. HTN
7. Hyperkalemia