Type of broad complex tachycardia characterised by a heart rate of more than 100 bpm and a QRS width of more than 120 ms

Aetiology

• Patients usually have structural heart disease e.g. CAD, previous MI, cardiomyopathy
• Other causes:
  • Electrolyte abnormalities such as hypokalaemia and hypomagnesaemia
  • Drugs that cause QT prolongation e.g. clarithromycin, erythromycin
  • Inherited channelopathies e.g. Romano-Ward syndrome, Brugada syndrome

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 features

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

Monomorphic VT

• Constant QRS morphology