Arrhythmias Flashcards
What is atrial flutter?
A form of SVT where a short circuit in the heart causes the atria to pump rapidly
What heart rate is seen in atrial flutter?
Atrial rate of 300 bpm
Ventricular rate of 150 bpm (but can be variable dependent on AV block)
What appearance does atrial flutter given on an ECG?
Sawtooth appearance
Why can the ventricular rate be variable in atrial flutter?
Dependant on how many impulses from the atria conduct through to the ventricles (a 2:1 ratio would result in 150bpm, a 3:1 ratio would result in 100bpm…)
What are the causes of atrial flutter?
COPD
Obstructive sleep apnoea
Pulmonary emboli
Pulmonary hypertension
What are the symptoms of atrial flutter?
Palpitations
Lightheadedness
Syncope
Chest pain
What is the treatment of atrial flutter in some haemodynamically unstable?
Direct current synchronised cardioversion + amiodarone
What is the first line management of atrial flutter in a haemodynamically stable patient?
Beta blocker (bisoprolol) or calcium channel blocker (verapamil or diltiazem)
What is the second line management of atrial flutter in a haemodynamically stable patient?
Cardioversion
What is the first line management of atrial flutter in a haemodynamically unstable patient?
DC cardioversion +/- amiodarone
What is supraventricular tachycardia?
Where abnormal signals from above the ventricles cause tachycardia
What is the pathophysiology of supraventricular tachycardia?
The electrical signals in the heart re-enter the atria from the ventricles - the electrical signal then travels down again through the AV node into the ventricles, causing a further ventricular contraction
What type of tachycardia is SVT?
Narrow complex tachycardia (QRS complex has a duration of less than 0.12 seconds)
What is paroxysmal SVT?
Where SVT reccurs and remits
What are the four types of narrow complex tachycardia?
Sinus tachycardia
SVT
AF
Atrial flutter
How does SVT appear on ECG?
Appears as a QRS complex, followed by a T wave, followed by another QRS complex
There are P waves present, but are buried in the T waves, and therefore cannot be properly seen.
What are the three types of SVT?
AV node re-entrant tachycardia
AV re-entrant tachycardia
Atrial tachycardia
What is AV node re-entrant tachycardia?
Most common type of SVT - where electrical signals re-enter atria through AV node
What is AV re-entrant tachycardia?
Where the electrical signal re-enters the atria through an accessory pathway (Wolff-Parkinson-White syndrome)
What is atrial tachycardia?
Not caused by the signal re-entering the atria, but by an abnormal atrial electrical activity
What is the accessory pathway called in Wolff-Parkinson-White syndrome?
Bundle of Kent
What are the ECG changes in Wolff-Parkinson-White syndrome?
Short PR interval
Wide QRS complex
Delta wave (slurred upwards stroke in the QRS complex)
What are the stages of acute SVT management?
Stage 1 - vagal manoeuvres
Stage 2 - adenosine
Stage 3 - verapamil or beta blocker
Stage 4 - Synchronised DC cardioversion
What are vagal manoeuvres?
Manoeuvres that stimulate the vagus nerve, increasing activity in the parasympathetic nervous system
What are examples of vagal manoeuvres?
Blowing hard against resistance
Carotid massage (on one side only) - contraindicated in carotid artery stenosis
How is adenosine given to patients with SVT?
Given as an IV rapid bolus into a central or lalrge vein - as it only acts for approx. 10 seconds
Which patients is adenosine avoided in?
Asthma
COPD
Heart failure
Heart block
Hypotension
What dose of adenosine is given in SVT?
Initially 6mg
then 12mg
then 18mg
What is the definitive treatment of Wolff-Parkinson-White syndrome?
Radiofrequency ablation of the accessory pathway
What is the most important complication of Wolff-Parkinson-White syndrome?
In combination with AF or atrial flutter, the chaotic atrial electrical activity can pass into the ventricles , causing a polymorphic wide complex tachycardia - leading to VF and cardiac arrest
What is the management of paroxysmal SVT?
Long term medication - beta blockers, calcium channel blockers, amiodarone
Radiofrequency ablation
What are the shockable rhythms?
Ventricular tachycardia
Ventricular fibrillation
What are the non-shockable rhythms?
Pulseless electrical activity
Asystole
What is narrow complex tachycardia?
A fast heart rate with a QRS complex of less than 0.12 seconds (3 small squares)
What is broad complex tachycardia?
A fast heart rate with a QRS duration of more than 0.12 seconds or 3 small squares
What are the types of broad complex tachycardia?
Ventricular tachycardia
Polymorphic ventricular tachycardia (such as torsades de pointes)
AF with bundle branch block
SVT with bundle branch block
What is the pathophysiology of torsades de pointes?
When QT interval is too long, repolarisation of the heart muscles is prolonged
Waiting a long time for repolarisation can cause abnormal spontaneous depolarisation
When there are recurrent contractions without normal repolarisation, this is called torsades de pointes
What does torsade de pointes look like on ECG?
Ventricular tachycardia, but the QRS complexes get progressively smaller, then larger, then smaller
What are the causes of prolonged QT?
Long QT syndrome - inherited
Medications
Electrolyte imbalances
What medications can cause prolonged QT syndrome?
Antipsychotics
Citalopram
Flecainide
Sotalol
Amiodarone
Macrolides
What electrolyte imbalances can cause prolonged QT?
Hypokalaemia
Hypomagnesaemia
Hypocalcaemia
What is the acute management of torsades de pointes?
IV magnesium (even if normal serum magnesium)
Debrillation if VT occurs
What is the management of prolonged QT?
Stop and avoid medications that cause prolonged QT
Correct electrolyte disturbances
Beta blockers
Pacemaker or implantable cardioverter defibrillator
What are ventricular ectopics?
Premature ventricular beats caused by random electrical discharges outside the atria
What is the appearance of a ventricular ecoptic on ECG?
An isolated, random, abnormal broad QRS complex on an otherwise normal ECG
What is bigeminy?
When every other beat is a ventricular ectopic
What is first degree heart block?
Delayed conduction through the AV node
- Causes a consistently long PR interval
What are the types of second degree heart block?
Mobitz type 1
Mobitz type 2
What is mobitz type 1 heart block?
Conduction through the AV node takes progressively longer until it fails
- Progressively longer PR intervals until one QRS complex is dropped
What is mobitz type 2 heart block?
There is usually a set ratio of P waves to QRS complexes
What is third degree heart block?
Complete heart block
- There is no association between the P waves and QRS complexes
What is the management of a broad complex tachycardia in a stable patient?
First line - IV amiodarone
What is the management of broad complex tachycardia in a haemodynamically unstable patients?
DC cardioversion
