A seven-year-old boy came to the paediatric primary care clinic 30 minutes before and while walking, presenting with a sensation of palpitations of sudden onset, without accompanying chest pain or dyspnoea. He had not exercised previously. No personal history of heart disease, nor family history of heart disease or sudden death.
On arrival at the health centre, the patient was conscious and oriented, with no signs of respiratory distress. Cardiac auscultation shows rhythmic tones at 170-180 beats per minute (bpm), with no murmurs. Peripheral pulses are rhythmic and symmetrical. Good capillary refill. Blood pressure (BP) systolic: 90 mmHg, 31st percentile (P31), diastolic: 65 mmHg (P76).
An electrocardiogram (ECG) is performed. Fig. 2 shows the measurement of the width of the QRS complex.

Given the electrocardiographic findings of wide QRS tachycardia without haemodynamic repercussions, the paediatrician started an amiodarone infusion (5 mg/kg, intravenous [IV]), and referred the patient to hospital by medical transport.
On arrival at the paediatric emergency department, the patient was asymptomatic except for the sensation of palpitations. Physical examination was as follows: weight 22.5 kg (P21), height 119.5 cm (P14), systolic BP 88 mmHg (P25) and diastolic 63 (P71). Conscious and oriented. Good perfusion. Cardiac auscultation with tachycardia without murmurs. Normal peripheral pulses. Rest normal.
After analysis of the ECG, the possibility of supraventricular tachycardia (SVT) conducted with aberrancy was considered, so it was decided to try to reverse the tachycardia with vagal manoeuvres (gag reflex, cold in the face), without success, so a bolus of adenosine was administered at 0.1 mg/kg IV leaving in sinus rhythm. A baseline ECG was performed, which showed no abnormalities. Blood tests showed ions and myocardial enzymes within the normal range.

The patient was admitted for 24 hours for observation, with no new episodes, an echocardiogram was performed, which was normal, and he was discharged with subsequent follow-up in Cardiology consultations, with a diagnosis of paroxysmal SVT with aberrant conduction.