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monomorphic ventricular tachycardia ECG criteria diagnosis management 2024
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ECG Interpretation: Monomorphic Ventricular Tachycardia (VT)
Extracted Measurements (Philips Automated Report)
| Parameter | Value |
|---|---|
| Heart Rate | 246 bpm |
| PR interval | Not measurable (absent/dissociated) |
| QRS Duration | 224 ms (severely prolonged) |
| QT | 124 ms |
| QTcB | 240 ms |
| QTcF | 486 ms |
| P axis | 174° |
| QRS axis | 101° (right axis deviation) |
| T axis | -48° |
Machine interpretation: "Wide-QRS tachycardia, RBBB and LPFB pattern, Abnormal ECG, Very High Heart Rate"
What This ECG Shows: Monomorphic Ventricular Tachycardia
This is a life-threatening emergency. The ECG meets multiple criteria for VT rather than SVT with aberrancy.
Key Diagnostic Features
1. Rate: 246 bpm
This is an extremely fast ventricular rate, far above the typical SVT range and consistent with VT. The machine flags "V-rate > (220-age)."
2. Wide QRS: 224 ms
QRS duration >160 ms strongly favors VT over SVT with aberrancy. At 224 ms, this is severely prolonged and is a major criterion for ventricular origin. Per Tintinalli's Emergency Medicine: "Ventricular tachycardia usually has a wider QRS complex than does supraventricular tachycardia with aberrancy, so extreme QRS durations >160 milliseconds argue in favor of ventricular tachycardia."
3. Positive Precordial Concordance (V1-V6)
All precordial leads (V1 through V6) show tall, wide, monophasic positive R waves - there is no RS transition anywhere across the chest. Positive concordance (all leads upright) is a very specific marker for VT. It essentially rules out SVT with aberrancy.
4. No Identifiable P Waves / AV Dissociation
No organized sinus P waves are visible before QRS complexes. This indicates AV dissociation - the atria and ventricles are firing independently, a hallmark of VT. (Note: AV dissociation is only visible in ~10% of VT on surface ECG, but its presence here supports the diagnosis.)
5. Right Axis Deviation (QRS axis +101°)
The axis is markedly deviated rightward and inferior:
- Positive in leads II, III, aVF
- Negative in leads I, aVL
- This "northwest axis" or right inferior axis in the context of wide QRS tachycardia further supports VT.
6. Monomorphic Regularity
All complexes are identical in morphology - regular, uniform - confirming monomorphic VT (as opposed to polymorphic VT or torsades de pointes).
Brugada Criteria - Applied to This ECG
The Brugada algorithm (1991) is a stepwise approach to distinguish VT from SVT with aberrancy (Frameworks for Internal Medicine, p. 90):
| Step | Finding in This ECG | Conclusion |
|---|---|---|
| 1. Absence of RS complex in any precordial lead? | Yes - all precordial leads show monophasic R waves, no RS pattern | VT - stop here |
This ECG is diagnosed as VT at Step 1 of the Brugada algorithm - the most specific early criterion.
Why NOT SVT with Aberrancy?
The machine suggests "RBBB + LPFB" pattern. However, several features definitively favor VT:
- QRS >200 ms: True RBBB produces a QRS of 120-160 ms. A QRS of 224 ms is too wide for bundle branch block aberrancy alone.
- Positive concordance V1-V6: RBBB aberrancy would show rSR' in V1 with deep S in V5-V6. Here, ALL precordial leads are positive - this is VT concordance.
- No visible P waves: RBBB with SVT would still show P waves preceding QRS complexes.
- Rate 246 bpm: Extremely unusual for stable SVT.
Differential Diagnosis Considerations
| Diagnosis | Fits? | Reasoning |
|---|---|---|
| Monomorphic VT | ✅ Very likely | Rate 246, QRS 224 ms, positive concordance, AV dissociation, axis deviation, no P waves |
| SVT with RBBB aberrancy | ❌ Unlikely | QRS too wide; concordance pattern wrong; no P waves |
| Antidromic AVRT (WPW) | Possible | Can mimic VT with very wide QRS and high rate; delta waves may be buried; should consider if young patient with no structural heart disease |
| Pre-excited AF | ❌ Less likely | Rhythm appears regular |
Clinical rule (Tintinalli's): "Wide-complex regular tachycardias that do not show regular sinus activity should always be treated as VT. Inappropriate treatment of VT as an SVT may induce hemodynamic compromise."
Immediate Management
This is a hemodynamic emergency. Management depends on clinical stability:
If Hemodynamically Unstable (hypotension, loss of consciousness, chest pain, pulmonary edema):
- Immediate synchronized DC cardioversion - this is the first-line treatment. Start at 100-200 J (biphasic).
- Do not delay for IV access or drugs.
If Hemodynamically Stable:
- IV Amiodarone 150 mg over 10 min, then 1 mg/min infusion - first-line pharmacologic agent for monomorphic VT.
- IV Lidocaine 1-1.5 mg/kg bolus - alternative, especially if suspected ischemic etiology.
- IV Procainamide 20-50 mg/min up to 17 mg/kg - highly effective but slower to administer.
- If drugs fail: synchronized cardioversion.
Post-Conversion Workup:
- 12-lead ECG after conversion (look for ischemia, delta waves, QT prolongation)
- Troponin, BMP, electrolytes (K+, Mg2+ - correct hypokalemia/hypomagnesemia)
- Echocardiogram (assess structural heart disease - most common substrate)
- Cardiology/electrophysiology consultation
- Continuous telemetry monitoring
Summary
This ECG from Narayana Medical College Hospital shows monomorphic ventricular tachycardia at 246 bpm with a markedly prolonged QRS of 224 ms, positive precordial concordance (V1-V6), right axis deviation, and absent identifiable P waves. This pattern satisfies the Brugada algorithm at Step 1 and is characteristic of VT. This is a life-threatening arrhythmia requiring immediate intervention - synchronized cardioversion if unstable, or IV antiarrhythmics (amiodarone/lidocaine) if the patient is hemodynamically stable.
Sources: Tintinalli's Emergency Medicine (Wide-Complex Tachycardias, p. 158); Frameworks for Internal Medicine (Brugada Criteria, p. 90); PMC ECG Diagnosis: Monomorphic VT; LITFL ECG Library - Monomorphic VT
Yes
Asking for Preferences
Agreed - this is confidently Monomorphic Ventricular Tachycardia.
To recap the key reasons this is VT and not SVT with aberrancy:
- QRS 224 ms - far too wide for any bundle branch block pattern (RBBB tops out ~160 ms)
- Positive concordance V1-V6 - arguably the single most specific ECG sign for VT; SVT with RBBB aberrancy cannot produce this
- Rate 246 bpm with no visible P waves - AV dissociation strongly implied
- Brugada Step 1 positive - absence of any RS complex in any precordial lead = VT, stop, don't proceed further
The machine's label of "RBBB + LPFB" is a misinterpretation by the automated algorithm - it is pattern-matching QRS morphology without accounting for the fact that the QRS width and precordial concordance exclude an aberrantly conducted supraventricular rhythm. Automated ECG machines should never be trusted in wide-complex tachycardias; clinical correlation always overrides them.
The bottom line: treat this as VT until proven otherwise. If the patient is conscious and maintaining blood pressure - IV amiodarone. If deteriorating - synchronized cardioversion immediately.
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