Ventricular Fibrillation Flashcards
What is VF?
In ventricular fibrillation, the ventricles merely quiver and do not contract in a coordinated way. No blood is pumped from the heart, so ventricular fibrillation is a form of cardiac arrest. It is fatal unless treated immediately.
rapid and irregular ventricular activation with no mechanical effects with no shapeless complexes
Give 3 presentations of VF:
1) pulselessness
2) rapidly unconscious
3) cardiac arrest
What usually causes ventricular fibrillation?
an ectopic ventricular beat
What are other causes of VF?
Heart failure
Cardiomyopathies
Shock (very low blood pressure), which can result from coronary artery disease and other disorders
Electrical shock
Drowning
Long QT syndrome (which may cause torsades de pointes ventricular tachycardia) including that due to very low levels of potassium in the blood (hypokalemia)
Drugs that affect electrical currents in the heart (such as sodium channel blockers or potassium channel blockers—see table Some Drugs Used to Treat Arrhythmias)
Brugada syndrome and other cardiac channelopathies
What treatment is used for VF?
electrical defibrillation
What is Brugada syndrome?
a genetic condition that accounts for part of a group of patients with idiopathic ventricular fibrillation who have no evidence of causative structural cardiac disease
Name two genes associated with Brugada syndrome:
1) SCN1B
2) SCN5A
What is long QT syndrome?
where ventricular repolarisation (QT interval) is greatly prolonged
Give two congenital syndromes associated with long QT syndrome:
1) Jervell-Lange-Nielsen syndrome (associated with congenital deafness)
2) Romano-Ward syndrome (not associated with congenital deafness)
- both mutations affect cardiac potassium and sodium channel gates
Give two causes of acquired long QT syndromes:
1) electrolyte disturbances (hypokalaemia, hypomagnesaemia, hypocalcaemia)
2) certain drugs (anti-psychotics, anti-depressants, macrolides and quinalones)
Give two presentations associated with long QT syndrome:
1) syncope
2) palpitations
Give 3 forms of management for long QT syndrome:
1) atrial or ventricular pacing
2) magnesium sulphate for acquired long QT syndrome
3) stop causative agents such as electrolyte disturbances
What are ventricular premature beats?
extra/ missed beats with broad QRS
What is torsades de pointes?
ventricular tachycardia characterized by sinusoidal waveforms on ECG
*Looks like VF but actually VT with varying/inverting axis.
*Due to prolonged QT interval (time for ventricular depolarisation and repolarisation
What is the treatment for torsades de pointes?
Treatment: remove offending medication. Shorten the QT interval with magnesium. May need pacing or DC Cardioversion
