Differential Diagnosis of Narrow Complex Tachycardia
| Arrhythmia | QRS rate(per min) | Atrial rate(per min) | Regular QRS? | Atrial activity | Effect of vagotonic manoeuvres or adenosine |
|---|---|---|---|---|---|
| Sinus tachycardia | 100–200 | 100–200 | Y | P wave precedes QRS | * |
| SVT | 150–250 | 150–250 | Y | Usually not seen or inverted P after QRS | † |
| Atrial tachycardia | 100–200 | 120–250 | Y | Abnormal shaped P wave, may outnumber QRS | ‡ |
| Atrial flutter | 75–175 | 250–350 | Y | ‘Saw-tooth’ in the inferior leads/V1 | ‡ |
| Atrial fibrillation | <200 | 350–600 | N | Chaotic (f waves) | ‡ |
| MAT | 100–130 | 100–130 | N | P waves of three or more morphologies | * |
SVT, supraventricular tachycardia (re-entrant tachycardia involving the AV node or an accessory pathway); MAT, multifocal atrial tachycardia.
* No effect or slight slowing.
‡ Slowing of ventricular rate.