Arrhythmias Flashcards
Cardiac arrest rhythms
Shockable:
- Ventricular tachycardia
- Ventricular fibrillation
Non-shockable rhythms:
- Pulseless electrical activity
- Asystole
Cardiac arrest protocol
Assess rhythm - shockable vs non-shockable
CPR 30:2
Adrenaline 1mg
- Give ASAP for non-shockable rhythms
- After third shock in VF/VT
- Repeat every 3-5m
Amiodarone 300mg
- Give after third shock in VF/VT
(- Further dose of 150mg after 5 shocks)
Reversible causes of cardiac arrest
Four Hs, Four Ts
Hypoxia
Hypovolaemia
Hypo/hyperkalaemia
Hypothermia
Thrombosis
Tension pneumothorax
Tamponade
Toxins
Tachycardia treatment summary
Unstable:
- Consider up to 3 synchronised shocks
- Consider amiodarone infusion
Stable with narrow complex (<0.12s QRS)
- AF - rate control with beta blocker or CCB (or rhythm control if in 48h)
- Atrial flutter - rate control with beta blocker
- SVT - vagal manoeuvres and IV adenosine
Stable with broad complex (>0.12s QRS):
- VT or unclear - amiodarone infusion
- If previously confirmed SVT with BBB - give adenosine as for normal SVT
What is the pathophysiology of atrial flutter?
Atrial flutter is caused by a “re-entrant rhythm” in either atrium.
This is where the electrical signal re-circulates in a self-perpetuating loop due to an extra electrical pathway.
This stimulates atrial contraction at 300bpm
What is atrial flutter associated with?
HTN
IHD
Cardiomyopathy
Thyrotoxicosis
Treatment of atrial flutter
Rate/rhythm control with beta blockers or cardioversion
Treat the reversible underlying condition (e.g. hypertension or thyrotoxicosis)
Radiofrequency ablation of the re-entrant rhythm
Anticoagulation based on CHA2DS2VASc score
What causes SVT?
Electrical signal re-entering the atria from the ventricles.
Normally the electrical signal in the heart can only go from the atria to the ventricles.
In SVT the electrical signal finds a way from the ventricles back into the atria.
Once the signal is back in the atria it travels back through the AV node and causes another ventricular contraction.
This causes a self-perpetuating electrical loop
What is paroxysmal SVT?
Situation where SVT comes and goes
Acute management of SVT
Valsalva manoeuvre
Carotid sinus massage
Adenosine
- Slows conduction through the AV node
- May cause brief period of asystole - however it is quickly metabolised and sinus rhythm should return
Alternative to adenosine is verapamil
DC cardioversion may be needed if medical treatment fails
Adenosine key things to remember
Avoid in asthma, COPD, heart block and severe hypotension
Warn patient about the scary feeling of dying / impending doom when injected
Give ASAP into large cannula
- Initially 6mg, then 12mg and further 12mg if there is no improvement between doses
Recurrent episodes of SVT
Measures can be taken to prevent these episodes
Medication - beta blockers, CCBs or amiodarone
Radiofrequency ablation
What is Wolff-Parkinson White syndrome?
Caused by extra electrical pathway connecting the atria and ventricles
ECG changes in WPW
Short PR interval (<0.12s) Wide QRS (>0.12s)
Delta wave - slurred upstroke to QRS
Definitive management of WPW, other treatment
Radiofrequency ablation of the accessory pathway is the definitive management
Medical therapy:
- Sotalol
- Amiodarone
- Flecainide
What is radiofrequency ablation? What conditions can it be used for?
Identifying the site of the arrhythmia and burning the abnormal area of electrical activity
These leaves scar tissue which will not conduct impulses
Can be curative and used in:
- AF
- Atrial flutter
- SVT
- WPW
What is torsades de pointes?
A type of polymorphic VT
It looks like normal ventricular tachycardia on an ECG however there is an appearance that the QRS complex is twisting around the baseline.
The height of the QRS complexes progressively get smaller, then larger then smaller and so on.
Who can torsades de pointes occur in?
It occurs in patients with a prolonged QT interval
What causes prolonged QT?
Long QT syndrome - inherited
Medications - antipsychotics, citalopram, flecainide, amiodarone, macrolide antibiotics e.g. erythromycin
Electrolyte disturbances e.g. low K, Mg, Ca
Acute management of Torsades de Pointes
Correct the cause - stop causative medications, correct electrolyte disturbances
Magnesium sulphate infusion
May need defibrillation if VT occurs
What is the risk of Torsades de Pointes?
It can progress into VT and cardiac arrest
Long term management of prolonged QT syndrome?
Avoid medications that prolong the QT interval Correct electrolyte disturbances Beta blockers (not sotalol) Pacemaker or implantable defibrillator
What are ventricular ectopics? Presentation?
Premature ventricular beats causes by random electrical discharges from outside the atria.
Presentation:
- Random brief palpitations
ECG - will show individual random, abnormal, broad QRS complexes on a background of a normal ECG.
Management of ventricular ectopics
Bloods -
- FBC (check for anaemia)
- U&Es (check for electrolyte disturbance)
- TFTs
Reassurance and no treatment in otherwise healthy people
Seek expert advice in patients with background heart conditions or other concerning features or findings (e.g. chest pain, syncope, murmur, family history of sudden death)
Types of heart block
First degree - Prolonged PR interval (>0.2s or 5 small squares)
- All P waves followed by QRS
Second degree:
- Type 1 - PR interval gradually increases until non-conducted P wave
- Type 2 - PR interval doesn’t lengthen but there is a set ratio of P waves to QRS
Third degree
- Complete dissociation between atria and ventricles
2:1 heart blocks
2 P waves for every QRS
Can be caused by Mobitz type 1 or type 2 - difficult to tell which
What is the risk with Mobitz type 2 and third degree heart block?
Risk of asystole
Treatment of AV node blocks/bradyarrhythmias
If unstable or risk of asystole (Mobitz Type 2, complete heart block or previous asystole):
- Atropine 500mcg IV
If no improvement:
- Further atropine doses up to 3mg
- Other inotropes e.g. isoprenaline
- Transcutaneous cardiac pacing
Common causes of AV node block
IHD - most common
Also - medications (BB, CCBs, digoxin), electrolyte imbalances, post-cardiac surgery,
What is the definitive treatment of Mobitz type 2 and complete heart block?
Pacemaker + ICD (implantable cardioverter defibrillator)
