What are the indications for a CT angiogram in a patient with suspected vascular disease?

Indications for CT Angiography in Suspected Vascular Disease

Coronary CT Angiography (CCTA)

CCTA is indicated as a first-line diagnostic test for patients with stable chest pain and intermediate pretest probability of coronary artery disease, and as an alternative to invasive angiography in low-risk patients presenting to the emergency department with acute chest pain. 1

Primary Indications for CCTA:

• Chronic coronary syndromes: CCTA is recommended (Class I-IIa) for diagnosis and risk stratification of obstructive disease in symptomatic patients based on pretest probability 1
• Acute chest pain in emergency department: CCTA should be considered (Class IIa, Level A) as an alternative to invasive angiography in patients without prior CAD history who have inconclusive initial assessment 1
• Pre-operative CAD assessment: CCTA is reasonable (Class IIa, Level B-C) in low-risk patients scheduled for valve surgery to exclude significant CAD 1
• Suspected coronary artery disease: CCTA assists in diagnostic evaluation of patients with suspected CAD, particularly when functional testing is equivocal 2

Specific Clinical Scenarios:

• Stable chest pain with intermediate pretest probability: Use CCTA or functional imaging based on local expertise and anticipated image quality 1
• Low-to-intermediate risk chest pain: CCTA demonstrates safety with low rates of major adverse cardiovascular events and significantly lower cost compared to standard care 3
• Coronary stent or bypass graft patency: CCTA may be considered (Class IIb, Level B) for stents ≥3 mm diameter in patients with new/worsening symptoms 1

Extracranial Carotid and Vertebral Artery Disease

CTA or MRA is indicated (Class I, Level C) when duplex ultrasonography yields equivocal or nondiagnostic results in patients with acute focal ischemic neurological symptoms. 1

Indications for Carotid/Vertebral CTA:

• Equivocal ultrasound findings: When duplex ultrasonography cannot be obtained or yields nondiagnostic results in patients with focal neurological symptoms 1
• Pre-intervention planning: CTA is reasonable (Class IIa, Level C) when intervention for significant stenosis is planned, to evaluate severity and identify intrathoracic or intracranial lesions not assessed by ultrasound 1
• Suspected complete occlusion: CTA may be considered (Class IIb, Level C) when complete occlusion is suggested by ultrasound to determine if the lumen is patent enough for revascularization 1
• Intracranial vascular disease: CTA is useful (Class IIa, Level C) when extracranial sources are not identified in patients with transient symptoms 1

Pulmonary Embolism

CT pulmonary angiography is the primary diagnostic test for suspected pulmonary embolism in patients with low or intermediate pretest probability and positive D-dimer, or when highly sensitive D-dimer is unavailable. 1

Indications for CT Pulmonary Angiography:

• Low pretest probability with positive D-dimer: A negative multidetector CT pulmonary angiogram alone can exclude PE (Level B recommendation) 1
• Intermediate pretest probability: Negative CT angiogram may require additional testing (D-dimer, lower extremity imaging) if clinical concern persists 1
• High pretest probability: Negative CT angiogram mandates additional diagnostic testing before excluding VTE 1

CT Venography Adjunct:

• Suspected iliocaval DVT: CT venography should be considered when ultrasound shows whole-leg swelling with normal compression or abnormal spectral Doppler in common femoral vein 4
• Combined PE/DVT evaluation: CT venography identifies DVT in additional 0-7.9% of patients when added to CT angiography, though not recommended routinely 4

Aortic Disease

CT angiography is indicated pre-operatively in acute aortic regurgitation to look for aortic dissection, and is reasonable (Class IIa, Level C) for patients undergoing aortic valve repair to evaluate leaflets and aortic root. 1

Specific Aortic Indications:

• Acute aortic regurgitation: CT imaging to evaluate for aortic dissection pre-operatively 1
• Bicuspid aortic valve: Aortic CT angiography is indicated (Class I, Level B) when morphology of aortic sinuses, sinotubular junction, or ascending aorta cannot be assessed by echocardiography 1

Giant Cell Arteritis

CTA is a useful but not first-line imaging modality for GCA diagnosis (sensitivity 67-73%, specificity 85-98%), reserved for when ultrasound is unavailable or to detect alternative causes of illness. 5

CTA Role in GCA:

• Alternative to ultrasound: CTA can be used for detection of luminal changes in extracranial arteries when ultrasound is unavailable 5
• Long-term monitoring: CTA may be used for monitoring structural damage at sites of preceding vascular inflammation 5
• Unspecific symptoms: CTA may be valuable to detect alternative causes of illness in patients with atypical presentations 5

Important Caveats

• Radiation exposure: Use lowest dose necessary; modern protocols can achieve <1 mSv for coronary CTA 6
• Contrast contraindications: Avoid in patients with severe renal dysfunction unless benefits outweigh risks 2
• Timing considerations: For GCA, imaging should be performed within 72 hours of starting glucocorticoids to maintain diagnostic accuracy 5
• Not for intrathecal use: Inadvertent intrathecal administration of contrast may cause death, seizures, or paralysis 2