NEUROIMAGING / DSA
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 and elective therapeutic endovascular procedures
- acute ischemic 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 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
Contraindications
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
- eGFR should be > 30 mL/min in patients receiving the iodinated contrast agent
- 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%
- renal insufficiency (results of laboratory tests must be obtained prior to the examination)
- pregnancy (relative contraindication for acute therapeutic procedures)
- blood clotting disorders and use of anticoagulants (relative)
- unstable cardiopulmonary/neurological status
Procedure
Preprocedural evaluation
- 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
Principles of contrast media administration and allergy premedication
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 required
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
- 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.)
→ local and systemic complications of endovascular procedures