12-lead electrocardiogram following the second dose of intravenous adenosine:
- Sinus rhythm with a ventricular rate of 158 bpm
- Tall/peaked P waves (P pulmonale) indicating right atrial enlargement
- Short PR interval (96 ms)
- Rightward QRS axis (130°)
- Resolution of ST-segment and T-wave changes
- Normal QTc 424 ms
Normal neonatal electrocardiogram.