Arrhythmias Flashcards
What is an arrhythmia?
An abnormal heart rhythm (caused by abnormal conduction of electrical activity)
What are the four cardiac arrest rhythms? How can these be categorised?
Shockable rhythms:
- VT
- VF
Non-shockable rhythms:
- PEA
- Asystole
Describe the appearance of atrial flutter on an ECG
“Sawtooth” appearance
Describe the acute and long term management of a stable patient with atrial flutter
Acute:
- Rate control with a beta blocker
Long term:
- Radiofrequency ablation of re-entrant loop
- Anticoagulation
Describe the pathophysiology of supraventricular tachycardia (SVT)
Caused by electrical signal re-entering the atria from the ventricles:
- AV nodal re-entrant tachycardia = signal travels back through the AVN
- AV re-entrant tachycardia = signal travels back through an accessory pathway (e.g. WPW syndrome)
Describe the acute management of a stable patient with SVT
- Vagal manoeuvres including Valsalva manoeuvre and carotid sinus massage
- Give adenosine (initially 6mg, followed by 12mg, followed by a further 12mg if required)
What is the name of the accessory pathway present in WPW syndrome?
Bundle of Kent
What is the definitive management for Wolff-Parkinson-White syndrome?
Radiofrequency ablation of the accessory pathway
What are the features of WPW syndrome on an ECG?
- Short PR interval (< 0.12 seconds)
- Wide QRS complexes (> 0.12 seconds)
- “Delta wave” (a slurred upstroke on the QRS complex)
How does adenosine work?
Slows conduction through the AV node, causing a brief period of bradycardia or asystole in order to “reset” back to normal sinus rhythm
What is Torsades de pointes?
Polymorphic VT
Torsades de pointes occurs in patients with…
What are the causes of this?
Torsades de pointes occurs in patients with prolonged QT
Causes of prolonged QT:
- Long QT syndrome (inherited)
- Meds, e.g. antipsychotics, citalopram
- Electrolyte disturbances (hypokalaemia, hypomagnesaemia, hypocalcaemia)
Describe the management of Torsades de pointes
- Correct the cause, e.g. meds, electrolyte disturbance
- Magnesium infusion (even if normal serum magnesium)
- Defibrillation if VT occurs
What is ventricular bigeminy?
Ventricular ectopic occuring after every sinus beat
What is first degree heart block? What ECG change does this cause?
Delayed conduction through the AV node, leading to a prolonged PR interval (> 0.2 seconds)
What are the types of second degree heart block?
- Mobitz type I (Wenkeback)
- Mobitz type II
Describe the ECG findings in Mobitz type I (Wenkeback) 2nd degree heart block
PR interval getting longer and longer until a QRS complex is dropped
Describe the ECG findings in Mobitz type II 2nd degree heart block
PR interval consistently prolonged, then beat is dropped (usually a set ratio of P waves to QRS complexes, e.g. 3:1)
What is third degree heart block? This is also known as…
Where there is no association between the P waves (atria) and QRS complexes (ventricles). This is also known as complete heart block.
Describe the acute treatment of a stable patient with bradycardia/AV node block
Start by observing
Describe the acute treatment of unstable patient with bradycardia/AV node block
- Atropine 500mcg IV (this can be repeated up to 6 times, max dose 3mg)
- Other inotropes e.g. noradrenalin
- Transcutaneous cardiac pacing (using a defibrillator)
What is the definitive long term management of patients with either:
- Symptomatic bradycardia
- High risk of asystole, e.g. Mobitz type II AV block, complete heart block
Permanent pacemaker (PPM)
How does atropine work?
Atropine is an antimuscarinic and works by inhibiting the parasympathetic nervous system (thereby increasing heart rate)
How can you determine which type of pacemaker a patient has based on their ECG?
- A sharp vertical line before EITHER the P wave OR the QRS complex = single-chamber pacemaker
- A sharp vertical line before BOTH the P wave AND the QRS complex = dual-chamber pacemaker
