Native Aortic Root Thrombus in 3-Year-Old Fontan Patient with Hypoplastic Left Heart Syndrome: Presentation and Echocardiographic Findings of This Life-Threatening Complication

• Native aortic root thrombus is a life-threatening complication in patients with HLHS. • Echo evaluation of the native aortic root is an important consideration. • Echo monitoring is a useful tool for assessment of thrombus response to therapy.