Narrow complex Tachyarrhythmias and differentiating clinical features
| Arrhythmia | Rate (bpm) | P-waves | QRS | Variability | Response to Adenosine/Vagal | Typical Demographic | Comments |
|---|---|---|---|---|---|---|---|
| Sinus Tachycardia | <220 (infants) <200 (adults) | Present, normal axis | Narrow | Variable | May transiently slow | All ages (triggered by fever, dehydration, pain) | Physiological response; not a primary arrhythmia |
| Atrioventricular Reentrant Tachycardia (AVRT) including WPW | >220 (infants) 150–250 (adults) | Retrograde (after QRS) or absent | Narrow | Fixed | Typically terminates | Neonates, children, adults with WPW | Most common SVT in infants; short RP interval |
| Atrioventricular Nodal Reentrant Tachycardia (AVNRT) | 140–280 | P-waves usually not visible (may be pseudo R’ in V1) | Narrow | Fixed | Typically terminates | Adolescents and adults | Most common SVT in adults; re-entry in AV node |
| Supraventricular Tachycardia (generic SVT) | >220 in infants >150 in adults | Absent or after QRS | Narrow | Fixed | Terminates with adenosine | All ages | Umbrella term; often AVRT or AVNRT |
| Atrial Flutter | Up to 500 (infants) 240–350 (adults) | Sawtooth flutter waves (best in II, III, aVF) | Narrow (unless with aberrancy) | Fixed, but may vary with AV block | May unmask flutter waves | Neonates, adults (rare in children outside neonatal period) | Often 2:1 AV conduction; adenosine unmasks diagnosis |
| Atrial Ectopic Tachycardia (AET) | Variable, often <250 | Visible; abnormal axis; precedes QRS | Narrow | Variable | Does not terminate | Children >6 months, adults | Focal atrial source; can cause tachycardia-induced cardiomyopathy |
| Multifocal Atrial Tachycardia (MAT) | 100–250 | ≥3 different P-wave morphologies | Narrow | Irregular | No effect | Elderly, COPD patients | Associated with severe lung disease; often confused with AF |
| Junctional Tachycardia (Ectopic or Automatic) | 70–180 | Absent or retrograde | Narrow | Variable | No effect | Children (post-surgery), adults (digitalis toxicity) | Automatic focus in AV junction; not re-entrant |