A 10-day-old baby girl presents to the emergency department with a history of poor feeding and lethargy.
Describe and interpret her initial 12-lead electrocardiogram:
- Narrow complex (QRS duration 46 ms) tachycardia (ventricular rate 313 bpm)
- No obvious P-waves
- Rightward QRS axis (130°)
- ST-segment depression throughout the precordial leads
- T-wave inversion in the inferior leads (II, III, aVF)
- Initial application of ice packs to the face failed to terminate the SVT.
- Restitution of normal sinus rhythm following the second dose of intravenous adenosine.