Arrythmias Flashcards
What can be some of the underlying causes of Sinus Tachycardia (increase in HR, normal rhythm) ?
Infection
Low blood pressure, compensatory mechanism
Anaemia
Thyrotoxicosis
Hypovolemia
Shock
Pulmonary embolism
Which drugs can cause Sinus Tachycardia?
Nicotine
B2-agonists
Levothyroxine
Salbutamol
Aminophylline
How is Atrial flutter treated?
Same as atrial fibrillation
What is the underlying cause of atrial flutter?
Re-entry circuit within the right atrium causing the ventricles to only beat once for every 2-4 atrial flutter waves
What happens in Wolff Parkinson White syndrome?
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
What are some of the causes of ventricular tachycardias?
AMI
Ischaemic heart disease
Myocarditis
Valvular disease
How does Torsades de pointes present on a ECG?
QT prolongation, which increases the risk of ventricular arrhythmias occurring
Which drugs cause QT prolongation and hence increase risk of Torsades de pointes?
Antiarhythmics (Class IA or III)
Erythromycin & clarithromycin
Tricyclic antidepressants
Cisapride
Terfenadine & astemizole
Haloperidol
Lithium
Phenothiazines
What happens in Ventricular fibrillation?
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.
What are some of the underlying diseases that can cause general arrythmias?
Thyroid disease- both hypothyroidism and hyperthyroidism
Electrolyte imbalances - magnesium, potassium and calcium
Hypertrophic cardiomyopathy
What are the three types of bradycardia arrythmias?
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
What are some of the causes of AV node disease?
AMI
Congenital defects
Infection
Surgery
Thyroid disease
Any drugs that have a negative chronotropic effect such as Beta blockers, Digoxin and Verapamil
What is the main management for bradycardia arrhythmias?
Acute management: Atropine STAT dose
Treat underlying cause
Permanent pacemaker
How does the ECG alter for first degree heart block?
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
How does the ECG appear for second degree heart block?
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
What happens in third degree heart block?
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.
What pre-medication and medication may be administered during the insertion of a pacemaker?
Pre-medication:
Antibiotics and pain relief
Procedure:
Wash of Gentamicin
After a pacemaker has been fitted, what happens for bradycardia?
Restart anticoagulants and eye drops
Consider restarting the rate control depending on indication (do they need this for their indication)/consider alternative
What is the loading dose of Amiodarone?
200mg tds 1 week → 200mg bd 1 week →
200mg od maintenance
Alternative unlicensed regime: 400mg tds
3 days → 200mg od maintenance)
What is the loading dose of Digoxin?
500mcg x 2 stat doses 6 hours apart →
125mcg od maintenance
What are some of the side effects of Amiodarone?
Bradycardia
Phototoxicity
Slate-grey skin
Taste disturbances
Corneal microdeposits
Liver dysfunction
Thyroid dysfunction
Pulmonary toxicity
What are the key counselling points for patients on Amiodarone?
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
Key side effects of Digoxin?
N&V
Blurred vision
Anorexia
Bradycardia
What is a key interaction between Amiodarone and Digoxin?
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.
How do you manage the interaction between Digoxin and Amiodarone?
If continued long term (1-4 weeks) reduce Digoxin dose by 50%, however this is normally stopped once ventricular rate is reduced
