What is considered sustained ventricular tachycardia (VT)?

Definition of Sustained Ventricular Tachycardia

Sustained ventricular tachycardia (VT) is defined as VT that lasts greater than 30 seconds in duration and/or requires termination due to hemodynamic compromise in less than 30 seconds. 1

Key Characteristics of Ventricular Tachycardia

Ventricular tachycardia itself is characterized by:

• A cardiac arrhythmia of 3 or more consecutive complexes
• Originating in the ventricles
• Rate greater than 100 beats per minute (cycle length less than 600 ms)
• QRS duration typically >120 ms without regularly occurring P:QRS association

Distinguishing Sustained vs. Nonsustained VT

The distinction between sustained and nonsustained VT is important for clinical management and prognostic implications:

Sustained VT:

• Duration greater than 30 seconds
• OR requires termination (typically via cardioversion or medications) due to hemodynamic compromise in less than 30 seconds
• May be further classified as:
  • Monomorphic: Stable single QRS morphology
  • Polymorphic: Changing or multiform QRS morphology at cycle length between 600 and 180 ms

Nonsustained VT:

• Three or more consecutive beats
• Terminates spontaneously in less than 30 seconds
• May also be monomorphic or polymorphic

Clinical Significance

The distinction between sustained and nonsustained VT is clinically important for several reasons:

• Mortality risk: Sustained VT is associated with higher mortality rates, even when hemodynamically stable. Data from the AVID registry showed that patients with "stable" sustained VT had mortality rates that tended to be higher than those with unstable VT (33.6% versus 27.6% at 3 years) 2

• Treatment approach: Sustained VT typically requires immediate intervention:

  • Hemodynamically unstable patients require immediate synchronized cardioversion 3
  • Hemodynamically stable patients may be treated with antiarrhythmic medications, though cardioversion is still often necessary 4

• Long-term management: Patients with sustained VT often require consideration for implantable cardioverter-defibrillator (ICD) therapy, particularly those with structural heart disease 1, 3

Pitfalls in Diagnosis

1. Misclassification: Failing to recognize that a VT requiring termination due to hemodynamic compromise is considered sustained even if it lasts less than 30 seconds

2. Underestimating "stable" VT: Assuming hemodynamically stable sustained VT is benign. Evidence shows that even "stable" VT carries significant mortality risk 2

3. Delayed recognition: Failure to rapidly diagnose sustained VT can lead to delayed treatment and worse outcomes

4. Misdiagnosis: Mistaking supraventricular tachycardia with aberrancy for VT, or vice versa, can lead to inappropriate management

Management Considerations

While not the focus of the definition question, it's worth noting that sustained VT requires prompt intervention:

• Hemodynamically unstable patients: Immediate synchronized cardioversion
• Hemodynamically stable patients: Consider antiarrhythmic medications (procainamide 10 mg/kg IV is recommended as first-line for monomorphic VT without severe heart failure or acute MI) 3, 5
• Long-term management may include ICD implantation, catheter ablation, and/or antiarrhythmic medications

Remember that the definition of sustained VT focuses on duration (>30 seconds) and/or the need for intervention due to hemodynamic compromise, regardless of the specific morphology or underlying etiology.