What Is DSA for Vertebral Artery Disease and Its Risks?

A catheter angiogram, often performed using a technique called digital subtraction angiography (DSA), is an invasive procedure that uses a series of X-ray images and contrast dye to create highly detailed videos of the blood flowing through your vertebral arteries. The term “digital subtraction” means a computer removes (subtracts) the bones and surrounding tissues from the image so the doctor can clearly see just the blood vessels ^[1].

Because it requires threading a catheter (a thin, flexible tube) through your blood vessels into the neck, it carries small but serious risks, such as stroke and bleeding ^[2]. For this reason, DSA is generally reserved for situations where safer, noninvasive scans cannot provide enough information, or when highly detailed measurements are needed to plan a surgical intervention ^{[3] [4]}. Being offered an invasive test can be frightening, but it is entirely reasonable to ask your doctor about the exact purpose of the test, the individualized risks, and to take time to consider your options.

What to Expect: Before, During, and After

While the exact protocols vary by hospital, a catheter angiogram generally follows this process:

• Before the procedure: Your team will check your kidney function and review your medications. Do not stop taking any medications (especially blood thinners like anticoagulants or antiplatelet drugs) without explicit instructions from your procedural team. You will likely be asked to fast for a few hours. Tell your team if you might be pregnant, as the procedure uses X-ray radiation ^[5].
• During the procedure: You will receive a local anesthetic at the puncture site (usually the wrist or groin) and you may be given conscious sedation to help you relax. Using fluoroscopy (a continuous series of X-ray images), the doctor will navigate the catheter to the arteries in your neck ^[1]. When the contrast dye is injected, it is normal to feel a temporary, intense warm sensation. Discuss beforehand whether this procedure is strictly diagnostic or if a treatment (like angioplasty or stenting) might be performed during the same session.
• After the procedure: The catheter is removed, and pressure or a closure device is applied to the access site to prevent bleeding. You will need to lie flat for a few hours (especially if the groin was used) and will need a ride home.

When to seek emergency help: After you go home, call emergency services immediately if you experience signs of a stroke (new weakness or numbness, facial droop, trouble speaking, severe new headache, confusion, or severe sudden imbalance). Contact your procedure team right away if you notice rapidly expanding swelling or bleeding at the puncture site, worsening pain, fever, or if the hand or foot on the side of the puncture feels cold, pale, or numb.

Why You Might Need DSA Instead of a CTA or MRA

Doctors usually start by evaluating your vertebral arteries with noninvasive tests like a CT angiogram (CTA) or an MR angiogram (MRA) ^{[3] [6]}. These are often sufficient for diagnosis. However, your care team might recommend a catheter angiogram if they need:

• Real-time, dynamic imaging: CTA and MRA usually capture a static “snapshot” of your blood vessels. If you have symptoms that only occur when you turn your head—a rare condition sometimes called Bow Hunter’s syndrome, where the vertebral artery is temporarily pinched by bone or muscle during movement—a specialized provocative catheter angiogram allows the doctor to safely watch the blood flow dynamically while you recreate the specific head movements under medical supervision ^{[7] [8] [9]}. (Note: Do not forcefully turn your neck or deliberately provoke severe symptoms on your own outside of a clinical setting.)
• Detailed surgical or stenting preparation: If you are a candidate for a stent or surgery, DSA may provide the most detailed information available about the inside of the artery (the lumen) ^[3]. It helps the surgeon evaluate blood flow dynamics and your collateral circulation—the backup blood vessels that help supply blood to your brain when a main artery is blocked ^{[10] [11]}.
• Clarity when other tests conflict: Sometimes CTA and MRA results are inconclusive or disagree with each other ^[4]. While DSA is not infallible (for example, an MRI is often better at showing the actual wall of the blood vessel ^[12]), DSA can provide complementary detail that helps piece together the full clinical picture ^[13].

Understanding the Risks of Catheter Angiography

While DSA provides a very clear picture of blood flow, it is an invasive procedure. Your doctor must believe that the information gained will change your medical management enough to justify these risks. Keep in mind that risk rates vary widely based on your personal health, the hospital, the doctor’s experience, and the complexity of your specific blood vessels.

• Stroke or transient ischemic attack (TIA): The most serious risk is that the catheter could scrape plaque off the artery wall or dislodge a small blood clot, sending it to the brain and causing a stroke ^[14]. General studies of diagnostic cerebral angiograms suggest the overall risk of neurological complications is roughly 0.36% to 0.62% ^{[14] [2]}. While most of these events are temporary, permanent stroke is a known risk (around 0.16% in one large study) ^[2]. Ask your doctor for an individualized risk estimate.
• Access-site complications: Bleeding, bruising, or a hematoma (a pooling of blood under the skin) at the puncture site can occur. Studies report the rate of a hematoma forming at the entry site is approximately 0.7% to 1.5% ^{[15] [2]}. Less common access risks include infection, an abnormal bulging of the artery (pseudoaneurysm), or arterial blockage.
• Kidney injury: The contrast dye must be filtered by your kidneys, which can lead to contrast-associated acute kidney injury ^{[2] [16]}. The risk depends heavily on your baseline kidney function (eGFR), hydration status, and other medical conditions. Your team will check your kidney function beforehand and can use hydration or other preventive measures if needed.
• Contrast reactions: Some people may experience an allergic reaction to the contrast dye ^[17]. Severe reactions are rare. Be sure to tell your care team if you have ever reacted poorly to medical contrast dye in the past (note: a shellfish or iodine allergy is not the same as a contrast dye allergy).
• Vessel injury: Navigating the catheter or forcefully injecting dye can scrape or tear (dissect) the artery being examined, particularly if the artery is unusually small or fragile ^{[18] [19]}.
• Radiation and Sedation: The procedure involves exposure to ionizing radiation from the X-rays, which carries long-term risks and rare risks of skin irritation during very long procedures ^[5]. Additionally, the sedatives or local anesthetics used carry their own small risks of breathing or blood-pressure issues.