Digital subtraction angiography (DSA)

Created 03/05/2021, last revision 14/04/2023

Digital subtraction angiography (DSA) is a fluoroscopic technique used to visualize the vascular system. Structures such as bone are digitally subtracted from the image, allowing for a better visualization of the blood vessels
the Seldinger method is used to access the vessels

the vessel is punctured with a hollow needle
a curved, soft-tip guidewire is inserted through the needle and positioned in the vessel lumen
a guidewire is held while the needle is carefully removed
the large catheter is threaded into the vessel lumen over the guidewire
the guidewire is removed
sheath now serves as a route for diagnostic catheters and other medical devices

Indications

acute ischemic stroke endovascular treatment (EVT)
- mechanical thrombectomy (MT)
- intra-arterial thrombolysis (IAT)
local intra-sinus thrombolysis in patients with cerebral sinus thrombosis → more
angioplasty and stenting of extra- or intracranial stenoses → carotid angioplasty with stenting
endovascular treatment of malformations (AVM, DAVF) and aneurysms

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balloon test occlusion (BTO) – assesses whether an artery can be temporarily/permanently occluded without significantly affecting brain perfusion
Wada test – short-term blockade of the function of a specific part of the brain after a selective intra-arterial administration of a short-acting barbiturate. It helps to determine which hemisphere controls language function and how important each hemisphere is for memory functions

Most contraindications are relative ⇒ assess risk-benefit

contrast-related contraindications
- renal insufficiency (results of laboratory tests must be obtained prior to the examination)
  - eGFR should be > 30 mL/min in patients receiving the iodinated contrast agent
  - use with caution in patients with eGFR < 45 mL/min
- hypersensitivity to iodinated contrast media (contrast agents)
  - reaction to contrast media is not a true allergy but a pseudoallergy in nature (there are no allergic antibodies present)
  - the contrast media cause mast cells to release histamine and other chemicals directly
  - the concentration of the contrast media affects the severity of an adverse reaction (higher concentration = higher risk of an adverse reaction)
  - the risk of serious, life-threatening reactions, including anaphylaxis, is approx. 0.1%
pregnancy (relative contraindication for acute therapeutic procedures)
blood clotting disorders and use of anticoagulants (relative)
unstable cardiopulmonary/neurological status

check:
- personal medical history (presence of atherosclerotic disease, diabetes, renal dysfunction, etc.)
- adverse reactions and previous exposure to iodinated contrast media
- prior vascular procedures
- review relevant vascular imaging studies (CTA, MRA, neurosonology)
the patient should be fasting (> 4h, except for acute interventions)
ensure adequate hydration (nephropathy prevention)
in diabetic patients, do not administer oral antidiabetic agents (e.g. metformin) in the morning
insert an intravenous cannula and urinary catheter
the patient must sign a consent form after being fully informed about the procedure and its risks

→ administration of an iodinated contrast agent

the angio suite should be equipped with a monitor and crash cart
standard monitoring during diagnostic DSA
- heart rate
- blood oxygenation (pulse oximetry)
- blood pressure (intermittently via a self-inflating cuff)
an anesthesiologist should be available if sedation or general anesthesia (GA) is required

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bed rest for at least 4-6 h in the supine position
careful compression and monitoring of the puncture site and peripheral blood supply
blood pressure monitoring
adequate hydration

the risk of permanent neurological deficit associated with diagnostic DSA is low (0.09-0.14%)
increased risk is associated with endovascular procedures (thrombectomy, coiling, stenting, etc.)