ECG rhythms Ventricular and arrest rhythms
Monomorphic ventricular tachycardia ECG
Monomorphic ventricular tachycardia. Regular, fast, wide QRS complexes of one shape. Small P waves, where visible between the complexes, run independently of them.
A 30-second recording of the heart model, played in real time. Run live starts the engine itself with this rhythm.
Computed by the TracingsMD heart model (Junkers engine): simulated for education, not a patient recording and not for diagnosis.
Measured on this recording
| Ventricular rate | 170/min |
|---|---|
| PR | — |
| QRS | 173 ms |
| QT | Not assessable in this rhythm |
| QTc (Bazett) | Not assessable in this rhythm |
| QTc (Fridericia) | Not assessable in this rhythm |
What it is
A regular wide-complex tachycardia arising in the ventricles: three or more ventricular beats in a row above 100/min (sustained if it lasts more than 30 seconds or needs termination because of instability). In monomorphic VT the QRS complexes have one shape. AV dissociation, fusion beats and capture beats confirm it, but their absence does not exclude VT.
How to read this strip
| Rate | Ventricular rate above 130/min. |
|---|---|
| Rhythm | Regular. |
| P waves | Hard to see; where a small notch appears between complexes it does not keep a fixed relation to the QRS (AV dissociation). |
| PR | No fixed PR. |
| QRS | Wide (≥120 ms), one shape. |
| QT | Not assessable in VT. |
Causes
- Scar from a previous myocardial infarction and coronary artery disease (most common).
- Cardiomyopathies: dilated, hypertrophic, arrhythmogenic right ventricular.
- Heart failure.
- Electrolyte disturbance (potassium, magnesium) and drug toxicity.
- Idiopathic VT in a structurally normal heart (for example from the outflow tracts).
What to consider
- Check for a pulse first: pulseless VT is cardiac arrest and is treated with CPR and defibrillation.
- VT with a pulse and signs of instability needs synchronized cardioversion.
- If stable, record a 12-lead ECG and seek expert advice; procainamide, amiodarone or sotalol, or elective synchronized cardioversion, are options (adenosine only if the rhythm is regular and monomorphic).
- Treat a regular wide-complex tachycardia as VT until proven otherwise, especially with known heart disease.
- After conversion, look for ischemia and electrolyte causes, and consider evaluation by a cardiologist for an implantable defibrillator (not needed for every VT, for example a fully reversible cause or idiopathic VT).
Key point
A regular wide-complex tachycardia in a patient with prior infarction is VT until proven otherwise; AV dissociation, when you can find it, is highly specific for VT.
Not to be confused with
- SVT with aberrant conduction — Where they can be seen between the complexes, P waves march through independently of the QRS (AV dissociation), which points to VT. Even when they cannot be found, treat a regular wide tachycardia in an unstable patient as VT.
- Torsades de pointes — Torsades is polymorphic: the QRS height twists around the baseline. Here every complex looks the same.
- Sinus tachycardia with bundle branch block — There is no P wave in a fixed relationship before each QRS.