ECG rhythms Atrial and supraventricular
Paroxysmal supraventricular tachycardia ECG
Paroxysmal supraventricular tachycardia (re-entry using the AV node). Regular, narrow, very fast, with no visible P waves before the QRS complexes, and an abrupt onset. The surface ECG alone does not show whether the circuit is inside the AV node (AVNRT, the most common) or uses an accessory pathway (AVRT); both depend on the AV node.
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 | 180/min |
|---|---|
| PR | Not assessable in this rhythm |
| QRS | 84 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 narrow-complex tachycardia from a re-entry circuit that uses the AV node: inside the node (AV nodal re-entry, the most common type) or through an accessory pathway (AV re-entry). It starts and stops abruptly. In typical AV nodal re-entry the P wave is hidden in the QRS (sometimes a small extra notch at the end of the QRS in V1, a pseudo-r′); in AV re-entry it is seen just after the QRS, in the ST segment.
How to read this strip
| Rate | Above 150/min. |
|---|---|
| Rhythm | Regular. |
| P waves | Not visible before the QRS. |
| PR | Not measurable. |
| QRS | Narrow. |
| QT | Hard to judge at this rate. |
Causes
- Usually a structurally normal heart with a re-entry substrate present from birth: dual AV nodal pathways or an accessory pathway (including Wolff–Parkinson–White).
- Triggers: premature beats, caffeine, alcohol, stimulants, fatigue, stress.
What to consider
- Unstable patients need synchronized cardioversion; stable patients start with vagal maneuvers, then adenosine, per the adult tachycardia algorithm and local protocols; if these fail, an IV beta-blocker or non-dihydropyridine calcium channel blocker, or synchronized cardioversion.
- Avoid diltiazem and verapamil with hypotension or a reduced ejection fraction; adenosine can trigger atrial fibrillation, so have a defibrillator ready if pre-excitation is possible.
- Record a 12-lead ECG during the tachycardia and after it ends: look for pre-excitation (a delta wave) in sinus rhythm.
- Recurrent episodes: refer for electrophysiology; catheter ablation cures most patients.
- A regular rhythm near 150/min may be flutter with 2:1 conduction; adenosine can unmask it.
Key point
Regular, narrow, very fast and sudden in onset suggests a re-entry circuit that depends on the AV node, which is why vagal maneuvers and adenosine can stop it.
Not to be confused with
- Sinus tachycardia — Sinus tachycardia has a clear P wave before each QRS and usually speeds up gradually.
- Atrial tachycardia (simulator) — Atrial tachycardia shows a distinct P wave before each QRS. Here no P wave is seen.
- Ventricular tachycardia — The QRS is narrow (under 120 ms), so the ventricles are activated through the normal pathway.