Can a computed tomography (CT) coronary angiogram detect a pulmonary arteriovenous malformation (AVM)?

Can a CT Coronary Angiogram Detect a Pulmonary AVM?

Yes, a CT coronary angiogram (CTA chest) can incidentally detect a pulmonary AVM if the lesion is within the field of view, but it is not the optimal imaging modality for this purpose and should not be relied upon for screening or definitive diagnosis.

Why CT Coronary Angiogram Is Suboptimal for PAVM Detection

Contrast Timing Issues

• CT coronary angiograms are timed specifically for the aorta and systemic arterial circulation, not the pulmonary vasculature 1
• The contrast bolus timing is optimized to capture coronary arteries during peak aortic enhancement, which does not coincide with optimal pulmonary artery opacification 1
• This timing mismatch may result in suboptimal visualization of the pulmonary arterial anatomy and PAVM architecture 1

Field of View Limitations

• Coronary CTA protocols typically focus on the heart and proximal great vessels, potentially missing PAVMs located in the peripheral lung fields 2
• The majority (65-83%) of PAVMs occur in the lower lobes, which may be incompletely imaged or excluded from a cardiac-focused protocol 3

Unnecessary Contrast Risk

• Administering IV contrast in patients with undiagnosed PAVMs carries a small but real risk of paradoxical air embolism 2, 1
• The American College of Radiology specifically notes that the high natural contrast inherent to pulmonary anatomy makes IV contrast unnecessary for PAVM diagnosis 2

The Correct Imaging Algorithm for PAVM

Initial Screening (If PAVM Is Suspected)

• Transthoracic contrast echocardiography (TTCE) with agitated saline is the recommended initial screening test, with 97-99% sensitivity and 99% negative predictive value 3
• TTCE uses a semiquantitative grading system (Grades 0-3) based on microbubble appearance in the left atrium after 3-8 cardiac cycles 2, 3
• Grades 2 and 3 indicate clinically significant shunts requiring further evaluation, with Grade 3 having an 87% positive predictive value for requiring treatment 2, 3

Confirmatory Imaging (After Positive TTCE)

• CT chest WITHOUT IV contrast is the preferred confirmatory test after a positive TTCE screening 2, 3
• Noncontrast CT provides high spatial resolution and accurately detects the number, size, location, and distribution of PAVMs 3
• The pulmonary vasculature has inherently high natural contrast on CT, making contrast administration unnecessary and avoiding air embolism risk 2, 3
• 3D reconstruction from noncontrast CT can predict PAVM angioarchitecture in 95% of cases 3

Alternative Confirmatory Imaging

• Contrast-enhanced MRA of the pulmonary arteries can be used in children and young adults to avoid radiation, with 92% sensitivity for PAVMs with feeding arteries ≥2 mm 2, 3

Common Pitfalls to Avoid

• Do not rely on chest radiography alone - it has only 60-70% sensitivity despite 98% specificity when classic findings are present 2, 3
• Do not use CTPA (CT pulmonary angiography) interchangeably with CTA chest - while CTPA is optimized for pulmonary vasculature evaluation, it still involves unnecessary contrast administration when noncontrast CT is adequate 2, 1
• Do not skip screening in high-risk populations - 70-90% of PAVM patients have hereditary hemorrhagic telangiectasia (HHT), and all HHT patients or their first-degree relatives should be screened 3

Clinical Bottom Line

If a pulmonary AVM is incidentally discovered on a CT coronary angiogram, it represents a fortunate finding rather than appropriate diagnostic imaging. The lesion should be further characterized with dedicated noncontrast chest CT to assess size, number, location, and treatment planning 2, 3. For any patient with suspected PAVM, begin with TTCE screening followed by noncontrast chest CT if positive 3.