A 2-day old neonate [gender: male; weight: 3.2 kg; height: 53cm] presented to the authors institution with an arterial oxygen saturation of 74%. The child was receiving 6 cm H2O continuous positive airway pressure therapy [FIO2: 0.5] and was treated with a prostaglandin E1 infusion [10ng/kg/min]. Transthoracic echocardiography revealed situs solitus, levocardia, normal systemic and pulmonary venous drainage and a 6 mm non-restrictive atrial septal defect with a left to right shunt. The atrioventricular connections were concordant. The aorta was arising from the right ventricle with no right ventricular outflow obstruction [Figure 1]. The pulmonary artery was arising from the left ventricle with confluent good size branch pulmonary arteries with posterior deviation of the conal septum [Figure 2]. A large perimembranous (conoventricular type)1 ventricular septal defect with an inlet [6 mm] and outlet [6 mm] extension and an additional tiny apical defect were demonstrated [Figure 3]. A patent ductus arteriosus [2.7 mm] shunting left to right was also present (not shown). A 2-dimensional echocardiography image in the parasternal long axis view displayed an obstruction to the left ventricular outflow tract [white arrow] and a color Doppler blood flow map demonstrated turbulence in the outflow tract [Figure 4A,B]. In the subcostal view with the probe tilted anteriorly, color flow Doppler mapping showed the ventricular septal defect and also the blood flow acceleration across the left ventricular outflow tract [Figure 5, videolip-1]. At the area of turbulence, the jet width was 0.234 cm[Figure 6A]. A continuous wave Doppler interrogation of the area demonstrated a gradient of ≈ 25 mmHg [Figure 6B]. 2-dimensional transthoracic echocardiography interrogation in the subcostal view identified the etiology of the left ventricular outflow tract obstruction [Figure 7, Videoclip-2]. What is the diagnosis? Figure 2Transthoracic echocardiography image showing the relationship between the pulmonary artery and the left ventricle. View Large Image Figure Viewer Download Hi-res image Figure 3Subcostal 4-chamber transthoracic echocardiography image showing the perimembranous ventricular septal defect. View Large Image Figure Viewer Download Hi-res image Figure 4A&B. Parasternal long axis transthoracic echocardiography 2-dimensional image showing the obstruction in the left ventricular outflow tract ‘white arrow’ [A], and turbulence in the outflow tract by a color Doppler blood flow map ‘white arrow’[B]. View Large Image Figure Viewer Download Hi-res image Figure 5Subcostal transthoracic echocardiography image showing color Doppler flow acceleration over the left ventricular outflow tract and a ventricular septal defect. View Large Image Figure Viewer Download Hi-res image Figure 6A&B. Subcostal transthoracic echocardiography image showing the width of the obstruction [A] and the pressure gradient across the obstruction [B]. View Large Image Figure Viewer Download Hi-res image Figure 7A subcostal transthoracic echocardiography view showing the etiology of the left ventricular outflow tract obstruction in systole. View Large Image Figure Viewer Download Hi-res image