This video features a one-day-old, 3kg neonate with a prenatal diagnosis of a cardiac mass. The postnatal transthoracic echocardiogram shows a large left ventricular mass occupying the majority of the left ventricular cavity and extending into the left ventricular outflow tract (LVOT). Other small masses also appear to be in the interventricular septum and on its right side. This suggests cardiac rhabdomyoma. A cardiac magnetic resonance imaging (MRI) confirms the findings. A brain MRI then shows features suggestive of tuberous sclerosis. Because of the large size of the mass and the presence of a gradient across the LVOT, the decision is made to proceed with resection.