Arrythmias Flashcards
What is arrythmia?
- Abnormal heart rhythms due to interrupted electircal signals that coordinate heart contraction
What causes arrythmia?
- Cardiac
- IHD
- LA diltation due to MR
- Cardiomyopathy
- Pericarditis
- Myocarditis
- abberant conduction pathways
- Non cardiac
- caffeine, smoking, alcohol
- medications
- metabolic disturbances
- phaechormocytoma
What medications can cause arrythmias?
- B2 agonist
- digoxin
- L-DOPA
- tricyclics
- doxorubicin (chemotherapy)
What metabolic disorders can cause arrythmia?
- K, Ca, Mg
- hypoxia
- hypercapnia
- metabolic acidosis
- thyroid disease
What is the presentation of arrythmia?
- palpitations
- chest pain
- presyncope/syncope
- hypotension
- pulmonary oedema
What are the 4 cardiac arrest rhythms?
- Shockable rhythm
- ventricular tachycardia
- ventricular fibrillation
- Non schokable rhythm
- pulseless electrical activity
- asystole
What are the examples of NCT?
- Sinus tachycardia
- AF
- Atrial Flutter
- Supraventricular Tachycardia
What are the examples of SVT?
- AVNRT - reentrant point back through AV node
- AVRT - reentrant point is accessory pathway
- Atrial tachycardia - electrical signal originates in atria other than SA node
What is the Px of Atrial Flutter?
- Normal: If SA node signal fail to reach AV node, automaticity foci in atrium will be triggered
In Atrial Flutter
- Irritable automaticity foci - reentrant rythm produced
- atria contracts at 300bpm
- ventricles contract 150bpm - long refractory period at AV node
What conditions is Atrial Flutter associated with?
- Hypertension
- Ischaemic heart disease
- Cardiomyopathy
- Thyrotoxicosis
How would you tx Atrial flutter?
- Same as AF
- Beta blocker / cardioversion
- Radiofrequency ablation
- Anticoagulation
What is the acute mx of patients c SVT?
- Vasalva manoeuvre
- Carotid sinus massage
- Adenosine
- Direct current cardioversion
How does adenosine work in SVT?
- Interrupts AV node/Accessory pathway during SVT
- Resets back to sinus rhythm
What dose of adenosine would you give for SVT?
Why must adenosine be given in a bolus dose?
- 6mg then 12mg then 12mg
- Ensures enough dose reaches the heart to interrupt the pathway
What will patients experience with adenosine?
- brief period of asystole/bradycardia - feeling of dying
Which patients would you avoid adenosine in?
- asthma
- COPD
- HF
- HB
- Severe hypotension
What is the long term mx for SVT?
- bb
- CCB
- amiodarone
- radiofrequency ablation
What ECG changes will you find in WPWS?
- Short PR interval
- narrow QRS in orthodromic
- borad QRS in antidromic
- d waves
What medications are contraindicated in WPWS and why?
- BB
- CCB
- Adenosine
- These medications reduce conduction through AV node > promote conduction through accessory pathway
What are the examples of BCT?
- SVT c BBB/aberrancy
- Antidromic WPWS
- VT
- AF c BBB/aberrancy
- VF
- Torsades
- Polymorphic VT
- Hyperkalaemia
What is the Px of Torsades de Pointes?
- Prolonged QT = prolonged repolarisation of myocytes
- Delay repolarisation > spontaneous depolarisations known as afterdepolarisations
- These depolarisations spread throughout ventricles
- Recurrent ventricular contractions occur
What is the prognosis of Torsades?
- Normally self limiting
- Can progress to VT > cardiac arrest
What causes prolonged QT?
- Long QT syndrome
- Medications
- antipsychotics
- citalopram (SSRI)
- flecanide
- sotalol
- amiodarone
- macrolide
- Metabolic
- Hypokalaemia
- Hypocalcaemia
- Hypomagnesaemia
How would you acutely Mx Torsades?
- Correct cause
- Mg infusion - if low Mg
- Defibrillation
