Ventricular Tachycardia Overview
Definition
- Ventricular Tachycardia (VT): Presence of 3 or more Ventricular Ectopic Beats (VEB) at a rate of >130 beats/min.
- Sustained VT: Duration >30 seconds.
- Can be classified as monomorphic or polymorphic VT.
Types of VT
Monomorphic VT
- Most common type.
- Often associated with Myocardial Infarction (MI).
Polymorphic VT
- Characterized by QRS complexes at 200 beats/min or more with changing amplitude and axis, giving a twisting appearance.
- Treatment approach is similar for both monomorphic and polymorphic VT.
Mechanisms of VT
- Enhanced automaticity: Ectopic pacemaker activity.
- Enhanced triggered activity.
- Re-entry mechanisms.
Predisposing Conditions
Channelopathies
- Lange-Neilsen syndrome: Long QT syndrome with deafness.
- Romano-Ward syndrome: Long QT syndrome without deafness.
- Brugada syndrome.
Other Electrophysiology Effects
- WPW Syndrome.
- Catecholamine sensitive polymorphic VT.
Drugs Causing QT Prolongation
- Clarithromycin, Erythromycin, Metoclopramide, Haloperidol, TCA, Methadone, Droperidol.
Electrolyte Imbalances
- Hypokalaemia, Hyperkalaemia, Hypomagnesaemia, Hypocalcaemia.
Other Conditions
- Hypothermia.
- Structural heart disease: LV dysfunction, coronary artery disease, MI, Hypertrophic Cardiomyopathy (HOCM).
Differentiating VT from Wide Complex SVT
Use the Brugada Algorithm:
- Is RS complex present in any lead? If NO, the rhythm is VT.
- Is the RS duration >100ms in any lead? If YES, the rhythm is VT.
- Is there AV dissociation (fusion or capture beats)? If YES, the rhythm is VT.
- Is rhythm not morphologically consistent with SVT (not looking like RBBB or LBBB)? If NO, the rhythm is VT.
- Fusion beats: Complex appears half-normal, half-abnormal.
- Capture beats: Normal-looking complex.
Management of VT
Pulseless VT
- Follow ACLS protocol.
- Immediate unsynchronized defibrillation.
- CPR with minimal interruption (30:2, 2 min cycles).
- Intubation, Oxygen, IV access.
- Administer Adrenaline (1mg every 3 mins).
- Amiodarone (300mg after the 3rd shock).
- Exclude reversible causes (4 Hs and Ts).
Clinically Compromised VT
- Hemodynamically unstable: synchronized shock x3.
- Oxygen, IV access.
- Rapid exclusion of reversible factors.
- Amiodarone (5mg/kg) > Infusion.
- Synchronized DC Shock (50J Bi, 100 Mono).
- Consider procainamide, lignocaine, sotalol.
- Repeat DC Shock (150 Bi, 360 Mono).
- Overdrive pacing.
Clinically Stable VT
- Controversial: debate between cardioversion and pharmacological treatment.
- Medical emergency as it can degenerate into unstable VT and VF.
- Oxygen, Amiodarone or sotalol.
- Cardioversion if medical therapy fails (requires sedation).
- Consider pacing if cardioversion is ineffective.
- Evaluate and treat the underlying cause (often Ischemic Heart Disease).
- If associated with long QT, consider Magnesium.
References and Additional Links