In recent years, there has been a marked reduction in surgical mortality for many complex forms of congenital heart disease. Treatment or palliative strategies vary but may include systemic-pulmonary central or Blalock-Taussig shunt. These shunts can be complicated by overcirculation, infection, thrombosis, and thromboembolism. Many diagnostic modalities are available to aide in diagnosis of postoperative shunt complications including echocardiography and cardiac catheterization but these may be invasive, inconclusive, or difficult to obtain adequate images. Computed tomography angiography (CTA) has many attributes that make it potentially useful in the evaluation of congenital heart disease and postoperative shunt complications. We report one patient where CTA guided the post-operative algorithm and appropriately identified a shunt narrowing despite repeated echocardiograms showing a patent shunt. These findings along with clinical suspicion appropriately guided us toward cardiac catheterization. To our knowledge, this is the first paper where CTA appropriately suspected a shunt narrowing in the absence of echocardiographic confirmation.