Definition of a Run of Ventricular Tachycardia
A "run" of ventricular tachycardia (VT) is defined as 3 or more consecutive ventricular complexes originating from the ventricles at a rate greater than 100 beats per minute (cycle length <600 ms). 1
Core Diagnostic Criteria
The term "run of VT" is clinically synonymous with nonsustained ventricular tachycardia (NSVT) when the episode terminates spontaneously in less than 30 seconds. 1 The minimum threshold is precisely:
- ≥3 consecutive ventricular beats 1
- Rate >100 bpm (cycle length <600 ms) 1
- Self-terminating in <30 seconds (distinguishes it from sustained VT) 1
Duration-Based Classification
The guidelines provide clear temporal distinctions that determine clinical significance and management:
- Nonsustained VT (NSVT): ≥3 beats, self-terminating in <30 seconds 1
- Sustained VT: >30 seconds duration OR requiring termination due to hemodynamic compromise in <30 seconds 1
The 30-second cutoff is the critical dividing line between nonsustained and sustained VT, regardless of the number of beats. 1, 2 Even a brief run causing hemodynamic instability requiring intervention is classified as sustained VT. 2, 3
Morphologic Subtypes
Runs of VT are further characterized by QRS morphology:
- Monomorphic: Stable single QRS morphology beat-to-beat 1
- Polymorphic: Changing or multiform QRS morphology beat-to-beat 1
Clinical Significance Based on Run Length
Short bursts of fewer than 5 beats are frequently observed and generally not associated with increased risk of sustained VT or ventricular fibrillation. 3 However, longer runs warrant increased concern:
- Runs ≥10 beats or ≥200 bpm are considered more concerning, particularly in hypertrophic cardiomyopathy 4
- Twenty beats of VT would be considered a "longer" run requiring serious risk assessment 4
- Frequent, longer, or faster runs carry greater prognostic weight 4
Critical Context: Structural Heart Disease
The clinical significance of any run of VT depends heavily on the presence of structural heart disease:
- In structurally normal hearts: Even brief runs are usually benign 3, 5
- In structural heart disease with reduced LVEF: Even brief episodes (≥3 beats) indicate significantly increased risk for sudden cardiac death 2, 3
- Post-MI patients with NSVT and LVEF ≤40%: Runs carry adverse prognostic significance and may warrant ICD evaluation if inducible at EP study 4, 3
Common Pitfall to Avoid
Do not confuse "number of beats" with clinical significance. The ACC/AHA guidelines emphasize that hemodynamic stability, underlying cardiac disease, and symptoms during the episode are equally important as duration. 3 A 10-beat run in a structurally normal heart may be benign, while a 5-beat run in a post-MI patient with LVEF 25% warrants aggressive evaluation. 4, 3