Heart Block

Question 1

What is first degree heart block (A-V Block)?

Answer 1

• When the PR interval is >0.2 seconds.

Management = none.

Question 2

What is second degree heart block?

Answer 2

When there is an intermittent block at the AV node which eventually results in a dropped beat

Question 3

Second degree heart block mobitz 1?

Answer 3

Progressive lengthening of the PR interval,eventually resulting in a dropped beat.

Usually vagal in origin.

Management = none. Unless assoc. with collapse or haemodynamic instability.

Question 4

2nd degree mobitz type 2:

Answer 4

Pathological, may progress to complete heart block (3rd degree)
- there is a fixed number of non-conducted P waves for the number of QRS complexes.

• PR interval is CONSTANT but there will be P waves without QRS complexes.

Usually 2:1 or 3:1

Permanent pacemaker indicated.

Treatment = ventricular pacing.

Question 5

Third degree heart block, what does the ECG show?

Answer 5

• There is no conduction from the atria to the ventricles which means there will be dual electrical output from the atria and ventricles.
• ECG: regular P waves, broad complex QRS with regular R-R interval.

Management = ventricular pacing

Question 6

Where is the QT segment?

Answer 6

Beginning of Q wave to the end of the T wave.

Question 7

Duration of QT prolongation?

Answer 7

Males = >450ms
Females = >470ms

Torsades de pointes is the life threatening complication of QT prolongation.

Question 8

Management of QT prolongation?

Answer 8

Monitoring and removal of cause If possible.

If genetic:

Low risk - lifestyle modification and beta blockers.

High risk - lifestyle mods + ICD +/- beta blockers.

Question 9

Genetic prolonged Qt syndrome

Answer 9

Inherited prolonged QT syndrome is associated with prolongation upon different situations such as stress, sudden auditors stimuli or swimming.