| Causes of tachyarrhythmias and differentiating clinical features |
| | Rate | P-waves | Variability | Most common demographic |
| Sinus Tachycardia | <220 | Present, normal morphology | Variable | Typically unwell children or systemic illness |
| Supra Ventricular Tachycardia | >220 (commonly 250-300 in infants) | Absent or after QRS | Fixed | |
| AVRT including WPW | | After QRS | | Neonates and children |
| AVNRT | | Not usually visible | | Adolescent |
Atrial Flutter
| Up to 500 beats/min in neonates (300 beats/min in children) with variable AV conduction being common | Saw tooth flutter waves (often only appreciated with AV block from adenosine) | Fixed but may appear irregular depending on AV conduction | Neonates (then not again until adulthood) |
| Atrial Ectopic Tachycardia | | Precede QRS with abnormal axis | Variable | May not respond to DC cardioversion or adenosine. Can cause cardiomyopathy. |
| Junctional Ectopic Tachycardia | 170-300 | Inverted | Variable | Post cardiac surgery |