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This ECG of a six year old child showing sinus tachycardia at a rate of around 140 per minute and T wave inversion in anterior leads suggesting juvenile pattern. This juvenile pattern may persist in adult life to a variable extend, more often in females. T wave in V1 gets inverted by about 72 hours after birth. If it remains upright it is a feature of right ventricular hypertrophy in the new born. This can occur in conditions like Tetralogy of Fallot. R/S ratio in V1 is more than 1 in the new born and the R wave height gradually decreases as the right ventricle which is dominant in the pre natal circulation regresses after the reduction of pulmonary vascular resistance. In this ECG R/S ratio is less than 1 and is normal for the age of six years.