Ventricular Tachycardia

Ventricular tachycardia (VT) is three or more consecutive ventricular beats at a rate over 100 beats per minute. Sustained VT lasts over 30 seconds or causes haemodynamic compromise.

Monomorphic VT: scar related reentry (post infarct, dilated cardiomyopathy, ARVC, sarcoidosis, Chagas disease, repaired congenital heart disease) or idiopathic (right ventricular outflow tract, fascicular VT; structurally normal heart).

Polymorphic VT: acute ischaemia, long QT (torsades de pointes), catecholaminergic polymorphic VT, Brugada syndrome.

Other causes: electrolyte disturbance (hypokalaemia, hypomagnesaemia), drug toxicity (digoxin, class I antiarrhythmics, tricyclics), cocaine, myocarditis.

Complications: haemodynamic collapse, degeneration to ventricular fibrillation, heart failure, sudden cardiac death. Mortality depends on substrate.

• Palpitations, dyspnoea, chest pain, presyncope, syncope, cardiac arrest.
• Pulse regular and rapid; hypotension, cannon a waves, variable first heart sound.
• Idiopathic VT: palpitations, rarely syncope.

• 12 lead ECG: wide complex tachycardia (QRS over 120 ms), regular; features favouring VT: AV dissociation, fusion and capture beats, QRS over 160 ms, concordance across the chest, northwest axis, Brugada algorithm, R wave peak time in lead II 50 ms or more. Treat wide complex tachycardia as VT until proven otherwise.
• Baseline ECG for scar, long QT, Brugada pattern, epsilon wave.
• Electrolytes, magnesium, troponin, drug levels, toxicology, thyroid.
• Echocardiography and cardiac MRI for structure and scar; coronary angiography for ischaemia.
• Electrophysiology study for mapping and risk stratification; exercise testing for catecholaminergic VT.
• Genetic testing when channelopathy or cardiomyopathy is suspected.

Acute

• Pulseless VT: defibrillation (biphasic 120 to 200 J), CPR per ALS.
• Unstable with pulse: synchronised cardioversion 100 to 200 J biphasic after sedation.
• Stable monomorphic VT: amiodarone 150 mg IV over 10 minutes (repeat once), then 1 mg/min for 6 hours, 0.5 mg/min for 18 hours; procainamide 20 to 50 mg/min up to 17 mg/kg; lidocaine 1 to 1.5 mg/kg then 1 to 4 mg/min (ischaemia); sotalol IV. Avoid verapamil in wide complex tachycardia of uncertain origin (except verapamil sensitive fascicular VT).
• Correct potassium (above 4.0 mmol/L), magnesium (2 g IV), ischaemia, and drug causes. Beta blockade for electrical storm (esmolol, propranolol), sedation, stellate ganglion block.

Long term

• ICD for secondary prevention in structural heart disease, and primary prevention per ejection fraction criteria.
• Beta blocker (metoprolol, bisoprolol), amiodarone 200 mg daily, sotalol 80 to 160 mg twice daily, mexiletine 150 to 300 mg three times daily (adjunct).
• Catheter ablation: first line for idiopathic VT (success 80 to 95%), for recurrent scar related VT or ICD shocks; epicardial approach in non ischaemic cardiomyopathy.
• Revascularisation for ischaemic VT; heart failure therapy; cardiac sympathetic denervation or stereotactic radioablation for refractory storms.
• Idiopathic VT: beta blockers, verapamil (fascicular VT 120 to 240 mg), flecainide, ablation.