Misdiagnosis of Pulmonary embolism in a Fontan's patient: When standard protocol CT Pulmonary angiogram is inadequate

Patients who have undergone a Fontan's procedure have an abnormal circulation that presents a unique challenge when performing computed tomography pulmonary angiograms. In a standard imaging protocol, contrast is injected into the upper limb veins that feed into the superior vena cava. In Fontan's patients the Computed tomography pulmonary angiograms bypasses the heart and preferentially fills the right lung, with only a small amount of mixture of contrast and noncontrast blood in the pulmonary arteries. In this article, we present the case of a 35-year-old female complaining of chest and abdominal pain with oxygen saturations of 85% on room air. Computed tomography pulmonary angiograms showed suboptimal imaging of the left lung and apparent filling defects in the right lung suggesting a radiological diagnosis of a pulmonary embolism. The abnormal flow and distribution of contrast in the pulmonary arteries can result in a false positive diagnosis of pulmonary embolism. To overcome this, experts advise using a dual-injection of contrast via upper and lower limb central veins to achieve optimal imaging.

Keywords: CTPA; Dual injection; Fontan's circulation; Fontan's procedure; Pulmonary embolism; Tricuspid atresia; Univentricle.