When is digital subtraction angiography (DSA) planned in patients with subarachnoid hemorrhage (SAH)?

Digital Subtraction Angiography (DSA) in Subarachnoid Hemorrhage (SAH)

Digital subtraction angiography (DSA) should be performed in patients with SAH when initial CTA is negative, when there is a diffuse aneurysmal pattern of SAH, or when definitive characterization of aneurysm anatomy is needed for treatment planning. 1

Initial Diagnostic Approach

• Non-contrast CT scan is the first-line diagnostic test for suspected SAH, with sensitivity approaching 100% within the first 3 days after onset 1
• If SAH is confirmed, vascular imaging should be performed to identify the cause of hemorrhage 1
• High-quality CTA is initially preferable to catheter angiography for detecting aneurysms with sensitivity >90% for most aneurysms 1
• However, CTA has limitations in detecting aneurysms <3mm in size, those adjacent to bone structures, and in providing complete characterization of aneurysm neck and relationship to parent vessels 1

Indications for DSA in SAH

Primary Indications:

• Negative CTA findings in patients with confirmed SAH 1
• Diffuse aneurysmal pattern of SAH on initial CT 1
• When detailed aneurysm characterization is needed for treatment planning 1
• When determining if an aneurysm is amenable to endovascular therapy 1

Secondary Indications:

• SAH with loss of consciousness (higher risk of missed small aneurysms on CTA) 1
• Blood located in the sulci (to evaluate for possible vasculitis) 1
• When planning endovascular treatment 1

Timing of DSA

• DSA should be performed urgently after SAH diagnosis when CTA is negative or inconclusive 1
• If initial DSA is negative in non-perimesencephalic SAH, repeat DSA should be considered, typically within 1-2 weeks 2
• For patients with aneurysmal SAH requiring treatment, DSA is often performed immediately before endovascular therapy 1

Special Considerations

• DSA with 3-dimensional rotational angiography is considered the gold standard for aneurysm detection and characterization 1
• 3D rotational angiography has been shown to identify aneurysms in 25% of patients with previously negative 2D angiograms 1
• In perimesencephalic SAH with negative CTA, the need for DSA remains controversial 1, 2
• False-negative rate of initial DSA is approximately 7%, particularly in non-perimesencephalic SAH patterns 2

Clinical Pitfalls to Avoid

• Relying solely on CTA for small aneurysms (<3mm) can lead to missed diagnoses 1
• Assuming perimesencephalic hemorrhage pattern is always benign without DSA confirmation 1, 2
• Failing to consider repeat DSA when initial angiography is negative in non-perimesencephalic SAH 2
• Overlooking secondary vascular lesions (like arteriovenous fistulas) that may coexist with aneurysms 3
• Proceeding with treatment based on CTA alone when aneurysm anatomy is complex or poorly visualized 4, 3

Treatment Planning

• After aneurysm identification, patients should be transferred to a tertiary center with neurosurgical expertise 1
• The aneurysm should be secured urgently (ideally within 24-48 hours) by endovascular coiling or microsurgical clipping 1
• For most patients eligible for both treatment approaches, endovascular coiling is preferred based on better long-term outcomes 1
• DSA provides the most detailed information for determining the optimal treatment approach 1