Unusual Pulmonary Arterial Filling Defect caused by Systemic to Pulmonary Shunt in the Setting of Chronic Lung Disease Demonstrated by Dynamic 4D CTA

Differentiating systemic artery-to-pulmonary artery fistula from pulmonary arteriovenous malformation: A case report

This report describes a rare case of a systemic artery-to-pulmonary artery fistula initially misdiagnosed as a pulmonary arteriovenous malformation in a 64-year-old male with severe emphysema. While a suspected pulmonary arteriovenous malformation was identified in the left lung on plain computed tomography, contrast-enhanced imaging revealed an aneurysmal nodule connected to the left inferior phrenic and internal mammary arteries, suggesting a systemic artery-to-pulmonary artery fistula. Selective angiography confirmed the diagnosis. The absence of pulmonary vein dilation on computed tomography is the key to differentiating a systemic artery-to-pulmonary artery fistula from a pulmonary arteriovenous malformation. Additionally, using contrast-enhanced computed tomography with both pulmonary artery and late phases helps prevent misdiagnosis of pulmonary embolism and may raise the suspicion of a systemic artery-to-pulmonary artery fistula.

Delayed systemic arterial-pulmonary arterial shunt simulating pulmonary embolism: An unusual case

This case report describes the imaging findings of an older-aged male presenting with infectious respiratory symptoms. Evaluation with routine contrast-enhanced CT of the chest demonstrated pulmonary artery filling defects initially treated as a pulmonary embolism. However, short-term repeat imaging during pulmonary angiographic and delayed phases demonstrated retrograde filling through a systemic arterial-pulmonary arterial shunt. Given the high prevalence of pulmonary embolism which is also the leading cause of pulmonary angiographic filling defects, this case highlights the importance for clinicians to maintain a differential diagnosis and consider alternative etiologies.

Serial assessment of computed tomography angiography for pulmonary and systemic arteries using a reduced contrast agent dose for the diagnosis of systemic artery-to-pulmonary artery shunts

PURPOSE

To evaluate the diagnostic performance and feasibility of a modified computed tomography (CT) scan protocol, we performed a serial assessment of the computed tomography angiography for pulmonary artery (CTA-P) and systemic artery (CTA-S) (CTA-PS) using a reduced contrast agent dose to diagnose systemic artery-to-pulmonary artery shunts (SPSs).

MATERIALS AND METHODS

Twenty-five patients who underwent multiphase contrast-enhanced chest CT and conventional chest angiography were included. Three image sets (CTA-P, CTA-S, and CTA-PS) were evaluated by two board-certified radiologists. The visualization of the CT image findings associated with SPSs, such as filling defects and enhancement in the pulmonary arteries, was evaluated using a 5-point scale.

RESULTS

The diagnostic performance (sensitivity, specificity, and accuracy) of CT imaging findings associated with SPSs in CTA-P and CTA-PS were as follows: CTA-P, 57.1%, 87.5%, and 62.0%; CTA-PS, 81.0%, 100.0%, and 84.0%. CT findings associated with SPSs in CTA-P were significantly sensitive to the CTA-PS protocol. There were no significant differences between the CTA-S and CTA-PS protocols. The area under the curve (AUC) of the CT imaging findings associated with SPSs in the CTA-P and CTA-PS groups was 0.835 and 0.911, respectively (P = 0.191). The AUC of the CT imaging findings associated with SPSs in CTA-S and CTA-PS were 0.891 and 0.926, respectively (P = 0.373).

CONCLUSION

CTA-PS using a reduced contrast agent dose protocol could improve the overall diagnostic confidence of SPSs, owing to better visualization of CT imaging findings associated with SPSs compared to individual assessments of CTA-P or CTA-S. Therefore, CTA-PS can be used as an alternative preembolization evaluation modality to conventional angiography in patients with hemoptysis suspected of having SPSs.

Systemic Artery to Pulmonary Artery Shunt Mimicking Acute Pulmonary Embolism, Unmasked by a Multimodality Imaging Approach

In this report, we describe the functional imaging findings of systemic artery to pulmonary artery shunt in V/Q SPECT CT imaging. A 63-year-old man with small-cell lung cancer underwent CT pulmonary angiography (CTPA) for suspected acute pulmonary embolism (PE). The CTPA showed an isolated segmental filling defect in the right lower lobe, which was initially interpreted as positive for PE but was actually the consequence of a systemic artery to pulmonary artery shunt due to the recruitment of the bronchial arterial network by the adjacent tumor. A V/Q SPECT/CT scan was also performed, demonstrating a matched perfusion/ventilation defect in the right lower lobe.

Systemic Artery-to-Pulmonary Artery Fistula Mimics Pulmonary Embolus

Systemic artery-to-pulmonary artery fistula (SA-PAF) is a rare phenomenon that can resemble a filling defect on computed tomography angiography (CTA). SA-PAF can be due to congenital or acquired etiologies and can alter the hemodynamics of the pulmonary circulation, with the most serious reported complication being hemoptysis, requiring embolization. We describe a case of an unusual SA-PAF between the right inferior phrenic artery and the right lower lobe pulmonary artery that mimicked an unprovoked pulmonary embolus (PE) on standard CTA in a patient with cardiomyopathy. This SA-PAF was interpreted on CTA as PE due to the presence of a filling defect, revealing that not all filling defects are PE. SA-PAF should always be considered when the clinical context or the imaging findings are atypical, specifically with an isolated filling defect visualized in the inferior lower lobe pulmonary artery. The false-positive PE was the result of mixing of systemic non-opacified blood with opacified pulmonary arterial blood.