Atrial fibrillation in a 12 year old male child

A 12 year old male child came to  JIPMER Hospital, Pondicherry, India with chief complaints of palpitation since 2 hours of duration. There was no history of giddiness, vomiting, chest pain, or breathless. There was NO past history of HTN/DM/RHD/CAD. Patient BP-110/70 mmhg, Pulse was 160 beats/min. ECG of the patient done in the emergency department is shown below.

ECG 1(Tachycardia ECG)(Click on the ecg to enlarge it)

ECG is showing narrow complex tachycardia at rate around 152 beats per minute,  irregular in nature, Left axis deviation, no visible P wave seen,ST segment with T wave inversion present in lead II,III,avF, V3-V6 so the diagnosis is atrial fibrillation with Left ventricular strain pattern

Rhythm strip of the patient

Rhythm strip of the patient show narrow complex irregular tachycardia with rate around 150 beats per minute.

ECHO heart of the patient was suggestive of severe concentric LVH with septal thickness around 18 mm and posterior wall thickness around 18 mm. There was no evidence of HOCM in the form of LVOT gradient.
 Patient BUN/Serum creatinine were within normal range. No evidence of Hypertension during his stay in the hospital.

Patient was given  intravenous amiodarone and he was converted to normal sinus rhythm. Later patient was started on tablet diltiazem.Patient was also started on aspirin in view of his CHADS2 score being 0. Presently patient is under workup to look for the etiology of concentric LVH, Atrial fibrillation.

Thank you.