Ventricular Arrhythmias Overview

Watch ▶Ventricular arrhythmias: Pathology review

Watch ▶Ventricular tachycardia: Clinical sciences

VA Overview

1️⃣ **Monomorphic** VT ⇒ single QRS **morphology**
2️⃣ **Polymorphic** VT ⇒ multiple QRS **morphologies** [Torsades de pointes] |

| Torsade de Pointes Tachycardia | 🔷 Associated with 1️⃣ Long QT syndrome 2️⃣ Proarrhythmic drugs 3️⃣ Electrolyte abnormalities (hypokalemia) | 🔷 Polymorphic ventricular tachycardia 🔷 QRS complexes that appear to twist around the isoelectric line | | Ventricular Fibrillation | 🔷 Myocardial infarction 🔷 Structural heart diseases | 🔷 Arrhythmic, fibrillatory baseline, usually > 300 bpm 🔷 Indiscernible QRS complexes |

Ventricular Tachycardia

General

• Rapid firing of more than 3 premature ventricular contractions (PVCs)
• Originating below the bundle of His, with a heart rate typically between 120-250 bpm.

Subtypes

• Classification by duration
  • Nonsustained ventricular tachycardia ⇒ VT lasting < 30 seconds
  • Sustained ventricular tachycardia ⇒ VT lasting ≥ 30 seconds
• Classification by morphology [monomorphic or polymorphic]
  • Monomorphic VT ECG (uniform QRS complexes)
  • polymorphic VT (varying QRS complexes)
    • See in Torsades de Pointes

• Other ECGs

Causes

• Associated with ischemic heart disease, non-ischemic cardiomyopathy, and structural heart abnormalities.
• Precipitating factors
  • Serum electrolyte abnormalities (eg, K, Mg)
  • Hypoxemia or acute myocardial ischemia
  • Elevated sympathetic tone (sepsis)

Management

• Non-sustained VT
  • Search for and address underlying causes.
• Sustained VT
  • No pulse (Pulseless VT)
    • ACLS Protocol ⇒ Immediate defibrillation.
  • Pulse present
    • Stable
      • Medication ⇒ IV Amiodarone (alternative options include Lidocaine or Procainamide).
    • Unstable
      • Synchronized cardioversion ⇒ Used if the patient is hemodynamically unstable.
• Long-term management
  • ICD (Implantable Cardioverter-Defibrillator) ⇒ Considered for patients at risk of recurrent VT or sudden cardiac death.
  • Medications ⇒ Beta-blockers or Amiodarone may be prescribed to suppress VT.
• UWT - Monomorphic nonsustained ventricular tachycardia

Torsades de Pointes

General

• Polymorphic ventricular tachycardia
• Characterized by cyclic, sinusoidal changes in the QRS complexes on ECG.

Risk

• Associated with prolonged QT interval, which can be ⇒
  • Congenital (Romano-ward, Jervell-and-Langnielsen syndromes)
  • Acquired due to ⇒
    • Electrolyte imbalances (hypocalcemia, hypokalemia, hypomagnesemia).
    • Drug-Induced Long QT Syndrome [toggle for more]

• Other ECGs

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Keep in mind

• When possible, patients receiving intravenous haloperidol or other QT-prolonging medications → should undergo ECG testing prior to administration.
• The medication must be withheld if the baseline-corrected QT interval is prolonged (eg, >450 msec). </aside>

Management

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Congenital LQTS is controlled with prophylactic Propranolol.

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