NEUROIMAGING / DSA
Digital subtraction angiography (DSA)
Created 03/05/2021, last revision 12/10/2022
- Digital subtraction angiography (DSA) is a fluoroscopic technique used for visualizing the vascular system. Structures such as bones are digitally subtracted from the image, which allows a better depiction of the blood vessels
- Seldinger method is used for access to the vessels
- the vessel is punctured with a hollow needle
- a soft curved tip guidewire is inserted through the needle and positioned into the vessel lumen
- a guidewire is held while the needle is carefully removed
- the large catheter is threaded over the guidewire into the vessel lumen
- the guidewire is removed
- sheath now serves as a route for diagnostic catheters and other medical devices
Indications
IndicationsAcute and elective therapeutic endovascular procedures
- acute stroke endovascular treatment (EVT)
- 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
Diagnosis of cerebral vascular diseases
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Functional tests
- balloon test occlusion (BTO) – assesses whether an artery can be temporarily/permanently closed 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 establish which hemisphere controls language function and how important each hemisphere is regarding memory functions
Detection of circulatory arrest in brain death diagnosis
→ see Brain death diagnosis chapter
Contraindications
Most contraindications are relative ⇒ assess risk-benefit
- contrast agent-related contraindications
- renal insufficiency (the results of the laboratory tests must be obtained prior to the examination)
- eGFR should be > 30 mL/min in patients receiving iodinated contrast
- discretion should be used in patients with eGFR < 45 mL/min
- hypersensitivity to iodinated contrast agents (contrast dye)
- reactions to contrast media are 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 contrast agent concentration affects the severity of an adverse reaction ⇒ higher concentration = greater risk of an adverse reaction
- severe, life-threatening reactions, including anaphylaxis, occur in approx. 0.1% of people receiving contrast agent
- renal insufficiency (the results of the laboratory tests must be obtained prior to the examination)
- pregnancy (relative contraindication with acute therapeutic procedures)
- blood clotting disorders and use of anticoagulant drugs
- unstable cardiopulmonary/neurological status
Procedure
Preprocedural evaluation
- check:
- personal medical history (presence of atherosclerotic disease, diabetes, renal dysfunction, etc.)
- allergies 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)
- secure adequate hydration (nephropathy prevention)
- in diabetic patients, do not administer peroral antidiabetics (metformin) in the morning
- insert an intravenous cannula and urinary catheter
- patient must sign an informed consent form after being fully informed about the procedure and its risks
Principles of contrast agent administration and allergy premedication
→ administration of an iodinated contrast agent
Monitoring during examination
- 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 demanded
Procedural technique
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Postprocedural care
- 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
Complications
- risk of a permanent neurological deficit following diagnostic DSA is low (0.09-0.14%)
- increased risk is associated with endovascular procedures (thrombectomy, coiling, stenting, etc.)
→ local and systemic complications of endovascular procedures
