Cardiology - Arrhythmias Flashcards
In a pulseless patient what rhythms are shockable or non-shockable?
Shockable
Ventricular tachycardia
Ventricular fibrillation
Non-shockable
Pulseless electrical activity
Asystole
What are narrow and broad complex tachycardias?
Narrow
Fast heart rate with QRS less than 0.12 seconds
Broad
Fast heart rate with QRS longer than 0.12 seconds
What are the 4 main differentials of narrow complex tachycardia?
Sinus tachycardia
Supraventricular tachycardia (treat with vagal manoeuvres and adenosine)
Atrial fibrillation (rate control or rhythm control)
Atrial flutter (rate control or rhythm control)
How should patients with narrow complex tachycardia with life-threatening features be treated?
Synchronised DC cardioversion under sedation or general anaesthesia
IV amiodarone added if DC shocks unsuccessful
What are the different types of broad complex tachycardia?
Ventricular tachycardia (IV amiodarone)
Polymorphic ventricular tachycardia e.g. torsades de pointes (IV magnesium)
Atrial fibrillation with bundle branch block (treated as AF)
Supraventricular tachycardia with bundle branch block (treated as SVT)
How should patients with life-threatening broad complex tachycardia be treated?
Synchronised DC cardioversion under sedation or general anaesthesia
IV amiodarone if shocks don’t work
What causes atrial flutter?
Re-entrant rhythm
Electrical signal re-circulates in self-perpetuating loop
What is a 2:1 conduction in atrial flutter?
Signal does not enter ventricles every time due to long refractory period of AVN
So two atrial contractions for every one ventricular contraction (2:1)
300 beats per minute so 150 beats per minute in the ventricles
How does atrial flutter appear on ECG?
Sawtooth appearance
Repeated P wave at 300 bpm
Narrow complex tachycardia
How is atrial flutter treated?
Anticoagulation based of CHADSVASc score
Radiofrequency ablation of re-entrant rhythm
When is a QT interval prolonged?
Men > 440ms
Women > 460ms
What does a prolonged QT interval actually mean?
Prolonged repolarisation of myocytes after contraction
Long repolarisation can cause spontaneous depolarisation in some muscle cells- afterdepolarisations
Afterdepolarisations spread throughout ventricles causing contraction before proper repolarisation
When this leads to recurrent contractions without normal repolarisation - torsades de pointes
How do you identify Torsades de pointes vs ventricular tachycardia?
QRS complexes get progressively smaller then bigger whereas ventricular tachycardia QRS stays about the same
What causes prolonged QT?
Long QT syndrome
Medications- antipsychotics, citalopram, flecainide, sotalol, amiodarone, macrolides
Hypokalaemia
Hypocalcaemia
Hypomagnesaemia
How do you manage a prolonged QT interval?
Stop and avoid medications which prolong QT interval
Correct electrolytes
Beta blockers (not sotalol)
Pacemakers or ICDs
What is the acute management of torsades de pointes?
Correct underlying cause
Magnesium infusion
Defibrillation if VT occurs
What are ventricular ectopics?
Premature ventricular beats caused by ventricular foci
How do patients present with ventricular ectopics?
Random extra or missed beats
Any age and in healthy patients
More common in patients with pre-existing heart conditions
How do ventricular ectopics appear on ECG?
Random
Broad QRS complexes
Otherwise normal
What is bigeminy?
Every other beat is a ventricular ectopic
How are ventricular ectopics treated?
Reassurance
Beta blockers if symptomatic
Outline heart block
First-degree
- Prolonged PR interval (over 5 squares)
- P wave always followed by QRS
Second degree Mobitz 1 (Wenckebach phenomenon)
- PR interval progressively gets longer until QRS not fired then it resets
Second degree Mobitz 2
- Intermittent failure through AVN
- Random absence of QRS complexes after P waves
- Risk of progression to complete heart block
- Usually set ratio e.g. 3:1 block
Third-degree heart block
- No relationship between P waves and QRS complexes
- High risk of progression to asystole
What can cause bradycardia?
Medications e.g. beta blockers
Heart block
Sick sinus syndrome
What is sick sinus syndrome?
Idiopathic degenerative fibrosis of the SAN causing dysfunction
What can sick sinus syndrome lead to?
Sinus bradycardia
Sinus arrhythmias
Prolonged pauses
When is there a risk of asystole?
Mobitz type 2
Third degree heart block
Previous asystole
Ventricular pauses over 3 seconds
How are unstable patients and those at risk of asystole managed?
IV atropine
Inotropes (isoprenaline or adrenaline)
Temporary cardiac pacing
Permanent implantable pacemaker
What options for temporary cardiac pacing are there?
Transcutaneous pacing (pads on patient’s chest)
Transvenous pacing
(catheter fed through venous system to directly stimulate heart)
