Arrythmias Flashcards
What are the 4 types of cardiac arrest rhythms?
Shockable rhythms
- Ventricular Tachycardia
- Ventricular Fibrillation
Non-shockable rhythms
- Other electrical rhythms excluding VT and VF
- Asystole (no significant electrical activity).
How do you treat a patient with tachycardia?
Treatment of tachycardia depends on whether the patient is stable or unstable.
Unstable
> 3 Synchronised Shocks
> Amiodarone infusion
Stable
In stable patients, management depends on whether the patient has a narrow (<0.12s) or wide QRS complex (>0.12s).
> Narrow QRS complex
- -> Atrial fibrillation –> rate control with beta blockers or calcium channel blocker (E.g. diltiazem). Rhythm control with cardioversion. Anticoagulant therapy based on CHA2DSVSc score.
- -> Atrial flutter –> rate control with beta blocker; rhythm control with cardioversion. Antiocagulant therapy based on CHA2DSVSc score.
- -> SVT –> valsalva maneuveur, carotid sinus massage, adenosine/verapamil or DC cardioversion.
> Wide QRS complex
Ventricular tachycardia or unknown –> give amiodarone
If the patient has SVT with bundle branch block = treat it as an SVT and treat them with Valsalva maneuverer, carotid massage, adenosine/verapramil and DC cardioversion if all else fails.
If QRS complex is irregular, it may be a variation of AF, so seek expert help.
What is atrial flutter?
Underlying pathophysiology of atrial flutter?
Characteristic ECG findings for atrial flutter?
Conditions associated with atrial flutter?
Treatment of atrial flutter?
Atrial flutter is due to an re-entrant rhythm in either atrium. This causes the electrical signal to perpetuate in a circulate loop. This leads to atrial tachycardia (300bpm). For every 2 atrial depolarisation, one manages to make it through to the ventricles due to the AV node, leading to ventricular tachycardia (150bpm).
Characteristic ECG finding:
- Sawtooth appearance on ECG, with p wave after p wave.
Conditions associated with atrial flutter includes:
- Hypertension
- Thyrotoxicosis
- Ischaemic heart disease
- Cardiomyopathy
Management of atrial flutter
- Similar to the management of atrial fibrillation
- Rate control with beta blockers or diltiazem. Rhythm control with cardioversion (pharmacological and electrical).
- Anticoagulant therapy based on the CHA2DS2VASc score.
- Treating the underlying cause of atrial flutter e.g. hypertension, thyrotoxicosis
- Radiofrequency ablation of the re-entrant rhythm
What is supraventricular tachycardia?
What are the different types of supra ventricular tachycardia?
What is the characteristic ECG finding for SVT?
What is the acute management of with stable SVT?
What is the management of unstable patients with SVT?
What is paroxysmal SVT?
What is the chronic management of paroxysmal SVT?
Supraventricular tachycardia is caused by electrical signals re-entering the atria from the ventricles. The electrical signal then goes through the AV node and causes another ventricular contraction. This is an example of a self-perpetuating electrical loop.
Different types of SVTs include:
- AV nodal re-entrant tachycardia –> this is where the re-entry point is back through the AV node.
- AV re-entrant tachycardia –> this is where the re-entrant point is an accessory pathway between the atria and the ventricles. For example, its the bundle of Kent in Wolf-Parkinson’s White syndrome.
- Atrial fibrillation –> this is not due to a re-entrant rhythm from the ventricles, but rather another site in the atrial produces electrical signals which passes through the AV node to cause the additional ventricular contraction.
Acute management of stable patients with SVT.
- Valsalva maneuverer –> ask the patient to blow hard against resistance e..g through a syringe.
- Carotid massage –> gently massage the carotid on one side with two finger.s
- Adenosine –> rapid infuse adenosine using a large proximal cannula (e.g. grey cannula in the antecubital fossa). Adenosine helps to stop the electrical conduction via the AV node and via the accessory pathway.
- Alternatively, you can use a calcium channel blocker called verapamil.
- If all else fails, then electrical cardioversion may be required.
Management of unstable SVT?
- 3 synchronised shocks
- Consider amiodarone infusion.
Paroxysmal SVT
- This is where the SVT reoccurs and remits in the same person over time.
Management of paroxysmal SVT
- Medicals (beta blockers, calcium channel blockers or amiodarone).
- Radiofrequency ablation to get rid of the accessory pathways.
When giving patients adenosine for SVT, which patients do you avoid?
What does do you give?
Patients to avoid giving adenosine to are:
- Asthma
- COPD
- Heart failure
- Heart blocks
- Severe hypotension
Dosage
- Initially 6mg, then 12mg, then 12mg if no improvement between doses.
What is Wolff-Parkinsons White Syndrome?
Underlying pathophysiology?
Characteristic ECG findings?
What is the definitive treatment for this condition?
What medications are contraindicated in patients with WPW and atrial flutter/atrial fibrillation? Why is this the case?
Supraventricular tachycardia (AV reentrant tachycardia) due to the presence of bundle of Kent. This re-entrant pathway leads to the over activation of the ventricles, leading to ventricular tachycardia.
Characteristic ECG changes
- Short PR interval (<0.12s)
- Wide QRS complex (>0.12s)
- Delta wave –> slurred upstroke of the QRS complex.
Definitive treatment for WPW
- Radio-frequency ablation of the bundle of Kent.
Most anti-arrhythmic medications (e.g. beta blockers, calcium channel blockers and adenosine) are contraindicated because they stop conduction through the AV node. This increases the likelihood of conduction through the accessory pathway. This increases the patient’s risk of developing polymorphic wide complex tachycardia.
What is Torsades de pointes?
Underlying pathophysiology?
Characteristic ECG findings?
Who are at risk of developing Torsades de pointes?
What is the acute and long term management of Torsades de pointes?
Torsades de pointes is a polymorphic (multiple shape) ventricular tachycardia.
Arises due to prolonging of the QT interval –> a prolonged QT interval means the heart is a waiting a long time to re-polarise after depolarising. This increases the likelihood of abnormal electrical activity arising before the repolarisation, called after-depolarisation, which causes abnormal ventricular contraction. Torsades de pointes increases the likelihood of the patient developing ventricular tachycardia.
Characteristic ECG findings
- Height of the QRS complexes gets progressively smaller, then larger, then smaller and so on.
- Prolonged QT interval.
People at risk of Torsades de points –> people that have a large QT interval.
> Hereditary
> Electrolyte disturbances e.g. hypocalcaemia, hypokalaemia, hypomagnesemia
> Medications e.g. anti-psychotics, citalopram, macrolide antibiotics, sotalol (beta blocker) and flecanide.
Acute management
- Remove any underlying cause e.g. correct any electrolyte disturbance, remove any medications associated with prolonged QT interval.
- Magnesium infusion, even in patients that have normal magnesium levels.
- Defibrillation if ventricular tachycardia occurs.
Long term management
- Avoid medications that prolong QT interval
- Sort out any electrolyte disturbance
- Beta blockers (avoid sotalol as this can prolong QT interval).
- Pacemakers or implantable defibrillators.
What is a ventricular ectopic?
Who is more common in?
ECG changes?
What is Bigeminy?
ECG changes?
How do you manage ventricular ectopics?
Random electrical discharges from the ventricles.
Found in all ages, but more common in people with pre-existing heart problems.
ECG changes –> random QRS complex in an otherwise normal ECG.
Bigeminy —> this is where ventricular ectopics occur so often, that it happens after every sinus beat.
ECG –> Normal sinus beat, followed by an ectopic beat, and then normal beat etc.
Management
- Check for any underlying cause e.g. anaemia, electrolyte disturbances and thyroid problems.
- If asymptomatic, no treatment required.
- If patient has background heart problem or other symptoms e.g. dyspnea, chest pain, palpitations, murmur –> seek expert help.
What is first degree heart block?
Second degree heart block - type 1?
Second degree heart block - type 2? Why is it dangerous?
Third degree heart block - type 3? Why is it dangerous?
Management of heart blocks?
Management of patients who have a high risk of asystole?
First degree heart block –> there is delayed conduction via the AV node, therefore PR interval is prolonged (>0.2s). But its regular, and every p wave is followed by a QRS complex.
Mobitz type 1 (Wenckebach’s phenomenon)
- This is where the atrial impulses becomes gradually weaker, until itd does not pass through the AV node. This leads to an increasingly prolonged PR interval, followed by no QRS complex. After failing to stimulate a ventricular contraction, the atrial impulse returns to being strong again. This cycle repeats.
Mobitz type 2
- This is where some p waves are not followed by QRS complexes, as there is a failure of atrial depolarisation passing through the AV node and initiating ventricular depolarisation. Usually, 3 p waves are followed by 1 QRS complex –> this is called a 3:1 block.
- Mobitz type 2 is particularly dangerous as there is a risk of asystole.
Third degree heart block
- This is where there is no relationship between the atrial depolarisation (p waves) and ventricular depolarisation (QRS complexes).
- Dangerous because there is a high risk of asystole.
Treatment of heart blocks, depends on whether the patient is stable or not.
> Stable –> just observe them.
> Unstable
First line
—> atropine (anti-cholinergic) (500mcg IV) to increase the patient’s heart rate.
No improvement,
- -> increase atropine by 500mcg up until 3mg.
- -> Other ionotropes e.g. noradrenaline.
- -> Transcutaneous cardiac pacing which is where you stimulate heart beating with an electrode that has been passed through the venous system and into the ventricles.
If patient have a very high risk of asystole (patients with Mobitz type 2 or third degree heart block)
- Temporary transcutaneous cardiac pacing
- Permnant implantable pacemaker if available.
