Ventricular Tachycardia

OVERVIEW

• Ventricular Tachycardia = 3 or more VEB at a rate of > 130 beats/min
• If > 30 seconds = sustained
• can be monophoric or polymorphic

TYPES

Monomorphic

• most common
• associated with MI

Polymorphic

• QRS at 200 beats/min or more which change amplitude and axis so they appear to twist around the baseline
• -> treatment is the same for both

MECHANISMS

• enhanced automaticity (ectopic pacemaker activity)
• enhanced trigger activity
• re-entry

PREDISPOSTING CONDITIONS

Channelopathies (Na+ and K+)

• Lange-Neilsen syndrome (long QT + deafness)
• Romano-Ward syndrome (long QT and no deafness)
• Brugada syndrome

Other electrophysiology effects

• WPW
• catecholamine sensitive polymorphic VT

Drugs that cause QT Prolongation

• clarithromycin
• erythromycin
• metaclopramide
• haloperidol
• TCA
• methadone
• droperidol

Electrolytes

• hypokalaemia
• hyperkalaemia
• hypomagnesaemia
• hypocalcaemia

Hypothermia

Structural heart disease

• LV dysfunction
• coronary artery disease
• MI
• HOCM

DIFFERENTIATING VT FROM WIDE COMPLEX SVT

Criteria for diagnosis of VT using the 4-step Brugada algorithm:

(i) Is RS complex present in any lead? -> if NO the rhythm is VT
(ii) Is the RS duration >100ms in any lead? -> if YES then the rhythm is VT
(iii) Is there AV dissociation? (fusion or capture beats) -> if YES then the rhythm is VT
(iv) Is the rhythm morphologically consistent with SVT (looks like RBBB or LBBB)? -> if NO the rhythm is VT

-> fusion beats = complex looks half normal and half abnormal
-> capture beats = normal complex seen

MANAGEMENT

PULSELESS

• ACLS protocol
• Immediate unsynchronised defibrillation
• CPR with minimal interruption (30:2, with 2 minute cycles)
• Intubation
• O2
• IV access
• Adrenaline 1mg Q3min
• Amiodarone 300mg (following 3rd shock)
• Exclude reversible causes (4 H’s and T’s)

CLINICALLY COMPROMISED

• Haemodynamically unstable, chest pain, ischaemia, heart failure, VR > 150/min -> synchronised shock (x 3)
• O2
• IV access
• Rapid exclusion of reversible factors (wire, PA catheter in RV, hypoK+ or Mg2+)
• Amiodarone 5mg/kg -> infusion
• Synchronised DC Shock (50J Bi, 100 Mono)
• Consider:
  -> procainamide 50mg/min
  -> lignocaine 1mg/kg
  -> sotalol 1mg/kg
• Repeat DC Shock (150 Bi, 360 Mono)
• Overdrive pacing

CLINICALLY STABLE

• controversial
• debate between cardioversion and pharmacological treatment
• still a medical emergency as can degenerate into unstable VT and VF

• O2
• Amiodarone or sotolol
• Cardioversion if medical therapy fails (quickly) – will need sedation
• Consider pacing if cardioversion no effective
• Evaluation and treatment of cause (usually IHD)
• If associated with long QT -> consider Mg2+

References and Links

litfl.com

• ECG Library — Overview of VT
• ECG Library — Monomorphic VT
• ECG Library — Fascicular VT
• ECG Library — Right Ventricular Outflow Tract (RVOT) tachyardia
• ECG Library — VT versus SVT with aberrancy