Cardiology: Arrhythmias Flashcards
What are the 4 possible rhythms in a pulseless patient?
1) ventricular tachycardia
2) ventricular fibrillation
3) pulseless electrical activity
4) asystole
Cardiac arrest rhythms can be shockable or non-shockable.
Which rhythms are shockable? Which are unshockable?
Shockable:
- ventricular tachycardia
- ventricular fibrillation
Non-shockable:
- pulseless electrical activity
- asystole
What is pulseless electrical activity?
All electrical activity except VF/VT, including sinus rhythm without a pulse.
What is asystole?
When there is no significant electrical activity.
What is a narrow complex tachycardia?
A fast heart rate with a QRS <0.12 seconds.
What are the four main differentials of a narrow complex tachycardia?
What does the treatment for each focus on?
1) Sinus tachycardia: treatment focuses on the underlying cause
2) Supraventricular tachycardia: treated with vagal manoeuvres and adenosine
3) Atrial fibrillation: treated with rate control or rhythm control
4) Atrial flutter: treated with rate control or rhythm control, similar to atrial fibrillation
What is a broad complex tachycardia?
A fast heart rate with a QRS complex >0.12 seconds.
What are the 4 groups of broad complex tachycardia?
1) Ventricular tachycardia of unclear cause
2) Polymorphic ventricular tachycardia, such as torsades de pointes
3) Atrial fibrillation with bundle branch block
4) Supraventricular tachycardia with bundle branch block
VT can be divided in monomorphic VT and polymorphic VT.
What is the difference?
Monomorphic: characterised by a single, stable QRS morphology with no beat-to-beat variation.
Polymorphic: has beat-to-beat variation in QRS shape and multiple QRS morphologies.
What is monomorphic VT most commonly caused by?
Myocardial infarction.
How is ventricular tachycardia of unclear cause treated?
IV amiodarone
How is atrial fibrillation with bundle branch block treated?
Treated as AF
How is supraventricular tachycardia with bundle branch block treated?
Treated as SVT
How is polymorphic ventricular tachycardia, such as torsades de pointes treated?
Treated with IV magnesium.
What is the QT interval?
From the start of the QRS complex to the end of the T wave.
What is the corrected QT interval (QTc)?
This estimates the QT interval if the heart rate were 60 beats per minute.
What is a prolonged QTc?
Men: >440 milliseconds
Women: >460 milliseconds
What does a prolonged QT interval represent?
Prolonged repolarisation of the myocytes after a contraction.