Arrythmias

Question 1

What can be some of the underlying causes of Sinus Tachycardia (increase in HR, normal rhythm) ?

Answer 1

Infection
Low blood pressure, compensatory mechanism
Anaemia
Thyrotoxicosis
Hypovolemia
Shock
Pulmonary embolism

Question 2

Which drugs can cause Sinus Tachycardia?

Answer 2

Nicotine
B2-agonists
Levothyroxine
Salbutamol
Aminophylline

Question 3

How is Atrial flutter treated?

Answer 3

Same as atrial fibrillation

Question 4

What is the underlying cause of atrial flutter?

Answer 4

Re-entry circuit within the right atrium causing the ventricles to only beat once for every 2-4 atrial flutter waves

Question 5

What happens in Wolff Parkinson White syndrome?

Answer 5

Additional electrical circuits which bypass the AV node (normal causes the delay) and instead conduct directly from the atria to the ventricles.
Ventricular rate can be up to 600 bpm

Question 6

What are some of the causes of ventricular tachycardias?

Answer 6

AMI
Ischaemic heart disease
Myocarditis
Valvular disease

Question 7

How does Torsades de pointes present on a ECG?

Answer 7

QT prolongation, which increases the risk of ventricular arrhythmias occurring

Question 8

Which drugs cause QT prolongation and hence increase risk of Torsades de pointes?

Answer 8

Antiarhythmics (Class IA or III)
Erythromycin & clarithromycin
Tricyclic antidepressants
Cisapride
Terfenadine & astemizole
Haloperidol
Lithium
Phenothiazines

Question 9

What happens in Ventricular fibrillation?

Answer 9

Rapid, uncoordinated contraction of the ventricular tissue, causing a decrease in cardiac output. Within 10-20 seconds of going into VF arrest, cardiac arrest will occur. Defibrillation is required.

Question 10

What are some of the underlying diseases that can cause general arrythmias?

Answer 10

Thyroid disease- both hypothyroidism and hyperthyroidism
Electrolyte imbalances - magnesium, potassium and calcium
Hypertrophic cardiomyopathy

Question 11

What are the three types of bradycardia arrythmias?

Answer 11

Sinus bradycardia - slow firing of the SA node

Sinus node disease - SA node fails to generate electrical impulses, due to fibrosis of conduction tissue

AV node disease - ‘Heart block’
Failure of the AV node to conduct electrical signals to the ventricles

Question 12

What are some of the causes of AV node disease?

Answer 12

AMI
Congenital defects
Infection
Surgery
Thyroid disease
Any drugs that have a negative chronotropic effect such as Beta blockers, Digoxin and Verapamil

Question 13

What is the main management for bradycardia arrhythmias?

Answer 13

Acute management: Atropine STAT dose
Treat underlying cause
Permanent pacemaker

Question 14

How does the ECG alter for first degree heart block?

Answer 14

There is a 1:1 ratio of P waves for each QRS complex however there is an abnormally prolonged PR interval, difficulty for the AV node to transmit to the ventricles

Question 15

How does the ECG appear for second degree heart block?

Answer 15

Not all P waves result in a QRS complex

Normally appears in a pattern 2:1 ratio - 2 P waves for every 1 QRS complex

Intervention is required

Question 16

What happens in third degree heart block?

Answer 16

There is no conduction at all through the AV node. Atrium continues to contract normally due to SA node conduction.
Ventricles will only contract due to automatic rhythm of AV node (escape rhythm) however this is much slower.

This is a medical emergency.

Question 17

What pre-medication and medication may be administered during the insertion of a pacemaker?

Answer 17

Pre-medication:
Antibiotics and pain relief

Procedure:
Wash of Gentamicin

Question 18

After a pacemaker has been fitted, what happens for bradycardia?

Answer 18

Restart anticoagulants and eye drops
Consider restarting the rate control depending on indication (do they need this for their indication)/consider alternative

Question 19

What is the loading dose of Amiodarone?

Answer 19

200mg tds 1 week → 200mg bd 1 week →
200mg od maintenance

Alternative unlicensed regime: 400mg tds
3 days → 200mg od maintenance)

Question 20

What is the loading dose of Digoxin?

Answer 20

500mcg x 2 stat doses 6 hours apart →
125mcg od maintenance

Question 21

What are some of the side effects of Amiodarone?

Answer 21

Bradycardia
Phototoxicity
Slate-grey skin
Taste disturbances
Corneal microdeposits
Liver dysfunction
Thyroid dysfunction
Pulmonary toxicity

Question 22

What are the key counselling points for patients on Amiodarone?

Answer 22

Wearing high factor UV sun protection
Warning patient about any changes in their vision ‘bright halo appearance’
Baseline thyroid and liver function needs to be checked at baseline and 3 months and thereafter
Report problems with breathing and SOB

Question 23

Key side effects of Digoxin?

Answer 23

N&V
Blurred vision
Anorexia
Bradycardia

Question 24

What is a key interaction between Amiodarone and Digoxin?

Answer 24

Amiodarone inhibits the key p-glycoprotein transport of Digoxin and therefore increases exposure by up to 50%, this is a major risk as Digoxin has a narrow therapeutic index. Amiodarone induced thyroid complications also increase Digoxin toxicity.

Question 25

How do you manage the interaction between Digoxin and Amiodarone?

Answer 25

If continued long term (1-4 weeks) reduce Digoxin dose by 50%, however this is normally stopped once ventricular rate is reduced