Supraventricular tachycardia may be caused by abnormal conduction pathways such as the Wolf-Parkinson-White syndrome, characterised on the ECG by a short P- R interval and an abnormal delta wave on the upstroke of the QRS complex. The child may develop sudden episodes of tachycardia associated with heart rates of 240beats/min, up to 300beats/min. These appear on ECG as narrow complex rhythms. The child may feel faint and uncomfortable during an arrhythmia. The arrhythmia may terminate spontaneously or be terminated by vagal manoeuvres such as brief immersion of the face in ice cold water, carotid sinus massage (massage to the carotid.
