Ventricular Tachycardia

Regular, fast heart rate, usually caused by underlying cardiac disease

Aetiology

• Patients usually have other heart conditions (CAD, previous MI, cardiomyopathy)

• Can also be idiopathic or iatrogenic (e.g. from medication)

Pathophysiology

Monomorphic VT

• Can be caused by increased automaticity, or due to a reentry circuit within the ventricle

• Most common cause of is scarring of the heart muscle from previous MI

Polymorphic VT

• Caused by abnormal ventricular repolarization e.g. long QT syndrome, drug toxicity, electrolyte imbalances

Clinical presentation

Symptoms

• Often results in pre-syncope (dizziness), syncope, hypotension and cardiac arrest

• May be remarkably well tolerated in some patients

Signs

• Pulse rate typically between 120 and 220 bmp

Investigations

ECG

• Constant QRS morphology

• Board complex rhythm

• Rapid rate

• QRS complex varies in amplitude

• Specific polymorphic VT associated with a long QT interval

• QRS complexes appear to twist around the isoelectric line

Management

• Unstable with pulse - DCCV

• Pulseless - defibrillation (see cardiac arrest)

• Stable - anti-arrhythmic drugs first line (amiodarone or lignocaine), DCCV if medical therapy fails