Arrhythmias

Question 1

What is an Arrhythmia?

Answer 1

Disturbances of heart rate, or rhythm - may be caused by changes in impulse formation or impulse conduction

Question 2

What is bradycardia?

Answer 2

A heart rate of less than 60bpm during the day and less than 50bpm at night

Question 3

What is tachycardia?

Answer 3

A heart rate of more than 100bpm

Question 4

Where are supra ventricular arrhythmias found?

Answer 4

In the atria and the AV node

Question 5

What do altercations in impulse formation involved?

Answer 5

Changes in automaticity

Triggered activity

Question 6

What do abnormalities in impulse conduction arise from?

Answer 6

Re-entry
Conduction block
Accessory tracts

Question 7

What is overdrive suppression?

Answer 7

When the SA node pacemaker is highest and is dominant over other latent pacemakers such as the AV node and Purkinje fibres

Question 8

What two ways can altered automaticity be classed?

Answer 8

1. Physiological (e.g. normal autonomic function)

2. Pathophysiological - when a latent pacemaker takes over as the result of a loss of overdrive suppression

Question 9

What causes a loss of overdrives suppression?

Answer 9

1. If SA node firing frequency is pathologically low
2. If conduction of the impulse from the SA node is impaired
3. If a latent pacemaker fires at an intrinsic rate faster than the SA node rate
4. In response to tissue damage i.e MI

Question 10

What are the two types of after depolarisation?

Answer 10

1. Early afterdepolarizations (EAD’s)

2. Delayed afterdepolarizations (DADs)

Question 11

At what stage of the action potential do EAD’s occur at?

Answer 11

Phase 2 and Phase 3

Question 12

Where do EAD’s most commonly occur?

Answer 12

In the Purkinje fibres when heart rate is slow

Question 13

What can sustained EAD’s lead to?

Answer 13

Torsades de pointes