Ventricular Tachycardia and Ventricular Fibrillation

Risk factors

• Coronary artery disease and prior MI (scar-related reentry — most common substrate)
• Heart failure with reduced EF (LVEF ≤35%)
• Hypertrophic, dilated, or arrhythmogenic RV cardiomyopathy
• Inherited channelopathies: long QT, Brugada, catecholaminergic polymorphic VT, short QT
• Electrolyte abnormalities: hypokalemia, hypomagnesemia, hypocalcemia
• QT-prolonging drugs: methadone, ondansetron, fluoroquinolones, macrolides, antipsychotics, antiarrhythmics
• Acute ischemia, myocarditis, cardiac sarcoidosis
• Stimulant use (cocaine, methamphetamine)

Pathophysiology

Most sustained VT in adults is scar-related macroreentry around fibrotic post-infarct tissue. Triggered activity (early or delayed afterdepolarizations) and abnormal automaticity also produce VT, especially in long QT syndromes (torsades de pointes) and in catecholamine-driven states. VF is multiple wandering wavefronts producing chaotic activation and no coordinated contraction.

Clinical presentation

Differential diagnosis

• Supraventricular tachycardia with aberrancy — Wide QRS from rate-related or pre-existing bundle branch block; Brugada and Vereckei algorithms favor SVT; respond to adenosine
• Antidromic AVRT (WPW) — Wide-complex tachycardia in pre-excited patient; treat with procainamide; AVOID AV nodal blockers
• Pre-excited atrial fibrillation — Irregularly irregular wide complex tachycardia in WPW; can degenerate to VF; treat with procainamide or DC cardioversion
• Hyperkalemia — Sine wave on ECG, peaked T waves, history of CKD, treat with calcium gluconate, insulin/D50, kayexalate
• Pacemaker-mediated tachycardia — Paced device patient with rapid wide complex; magnet application terminates
• Artifact — Patient awake and well-appearing, baseline ECG between artifact, regular underlying rhythm visible

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[Wide-complex tachycardia] --> B{Pulse?}
  B -->|No| C[Pulseless VT / VF<br/>Defibrillate 200 J<br/>CPR + epi + amiodarone]
  B -->|Yes| D{Hemodynamically<br/>stable?}
  D -->|No| E[Synchronized cardioversion<br/>100 J biphasic]
  D -->|Yes| F[12-lead ECG<br/>IV antiarrhythmic:<br/>amiodarone or procainamide]
  F --> G{Conversion?}
  G -->|No| E
  G -->|Yes| H[Identify cause<br/>Echo, electrolytes, ischemia]
  H --> I{Structural disease?<br/>EF ≤35%?}
  I -->|Yes| J[ICD ± ablation]
  I -->|No| K[Channelopathy workup<br/>or idiopathic VT ablation]

Treatment

Complications

• Sudden cardiac death
• Anoxic brain injury after prolonged arrest
• Recurrent appropriate ICD shocks (electrical storm)
• Cardiomyopathy from incessant VT (tachycardia-mediated)
• ICD complications: lead displacement, infection, inappropriate shocks

PANCE pearls

• When in doubt about a wide-complex tachycardia, treat as VT until proven otherwise.
• AV dissociation, capture beats, and fusion beats are highly specific for VT.
• Torsades de pointes = polymorphic VT with twisting QRS axis in setting of long QT — give magnesium first.
• Brugada syndrome: pseudo-RBBB with coved ST elevation in V1-V2, autosomal dominant, risk of SCD especially at night; ICD if symptomatic.
• WPW with atrial fibrillation: AVOID AV nodal blockers (adenosine, beta-blocker, CCB, digoxin) — they accelerate the accessory pathway and can precipitate VF.

Images

References

• AHA 2020 ACLS — 2020 AHA Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care (Panchal et al., Circulation 2020)
• AHA/ACC/HRS 2017 VA/SCD — 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death (Al-Khatib et al., Circulation 2018)
• MADIT-II — Prophylactic Implantation of a Defibrillator in Patients with MI and Reduced EF (Moss et al., NEJM 2002)
• SCD-HeFT — Amiodarone or an ICD for Congestive Heart Failure (Bardy et al., NEJM 2005)