Degrees of Carotid Stenosis: What Your Percentage Means
The degree of carotid stenosis is how much a carotid artery in your neck has narrowed, shown as a percentage. Doctors usually group it into three main ranges: under 50% (mild), 50% to 69% (moderate), and 70% to 99% (severe). A nearly closed artery is called near occlusion, and a fully blocked one is called occlusion.
Your percentage is an important number, but it is not the only one that matters. Whether you have had carotid stenosis symptoms, such as a mini-stroke, can change your treatment plan just as much.
Let’s see the detailed discussion now-
Key Takeaways
- Under 50% is mild, 50% to 69% is moderate, and 70% to 99% is severe.Each range comes with a different level of concern.
- Symptoms matter as much as the number.A recent mini-stroke or stroke can change what your doctor recommends.
- The method affects the percentage.The same blockage can read higher or lower depending on how it is measured.
- Ultrasound gives an estimate.A CT or MR angiogram is often used to confirm the degree before a procedure.
- At 70% or more, treatment is personal.It depends on your symptoms, overall health, and the latest evidence.
What Do the Degrees of Carotid Stenosis Mean?
Each degree describes how much of the artery’s opening is blocked by plaque. The higher the percentage, the less room blood has to flow through.
| Degree | Category | What it means | Typical next step |
| Under 50% | Mild | Some plaque, but blood still flows well. | Medical therapy and follow-up checks. |
| 50% to 69% | Moderate | A noticeable narrowing. | Medical therapy; a procedure is often recommended if you have had symptoms. |
| 70% to 99% | Severe | Most of the opening is blocked. | A procedure is often discussed, especially if you have had symptoms. |
| Near occlusion | Severe | The artery is almost completely closed. | Discussed case by case with your specialist. |
| Occlusion (100%) | Complete blockage | No blood flows through that artery. | Discussed case by case with your specialist. |
Please keep in mind that the “typical next step” is a general guide, not a plan. Your vascular surgeon will look at your whole health picture before recommending anything.
How Is the Percentage Measured?
The percentage compares the narrowest part of the artery with a normal section. Two main methods exist, and they use different reference points.
- NASCET method:compares the narrowest point with the normal artery further up the neck, past the widened area called the carotid bulb. This is the most widely used method today and is considered the current standard (Vascular Medicine, 2021).
- ECST method:compares the narrowest point with the estimated original width of the carotid bulb itself. Because the bulb is wider, this method gives a higher percentage for the same blockage.
The difference is not small. A 70% narrowing by the NASCET method equals about 80% by the ECST method (published review, PMC). If you are comparing reports from different places, check which method was used.
The first test is usually a vascular ultrasound evaluation, which estimates the degree of narrowing based on how fast blood moves through the narrowed area.
How Do You Read Your Carotid Ultrasound Report?
A carotid ultrasound report often lists a few numbers along with the percentage. Here is what they mean in plain language:
- PSV (peak systolic velocity):the fastest speed of blood through the narrowed spot. Blood speeds up as the artery narrows, like water through a pinched hose.
- EDV (end-diastolic velocity):the blood speed between heartbeats.
- ICA/CCA ratio:compares blood speed in the internal carotid artery with the common carotid artery lower in the neck.
Many vascular labs base their grading on criteria set by a 2003 expert consensus of the Society of Radiologists in Ultrasound (Radiology, 2003):
| Degree | Peak systolic velocity (PSV) |
| Under 50% | Under 125 cm/s |
| 50% to 69% | 125 to 230 cm/s |
| 70% or more | Over 230 cm/s |
Labs may also use the EDV and the ICA/CCA ratio to support the grading. One multicenter study found these criteria tended to overestimate both moderate and severe narrowing compared with angiography, and it recommended a higher PSV cutoff for 50% narrowing (Vascular Medicine, 2021).
So your report may follow slightly different numbers, and ultrasound remains an estimate. That is why a CT or MR angiogram is often used to confirm the degree before a procedure.
Why Do Symptoms Change the Treatment Plan?
Doctors sort carotid stenosis into two groups:
- Symptomatic:you have had a stroke, mini-stroke (TIA), or brief vision loss in one eye caused by the narrowed artery, usually within the past six months.
- Asymptomatic:the narrowing was found on a scan, but you have had no such symptoms.
A recent symptom usually means plaque in the artery may have sent a clot or debris toward the brain or eye. That raises the short-term risk of another event, so the same percentage may be treated more urgently when it comes with symptoms. When the narrowing is under 50% and you have had symptoms, procedures are generally not recommended, and medical therapy is the main approach.
What Medical Therapy Helps at Every Degree?
No matter your percentage, medical therapy is the foundation of care. It aims to slow atherosclerosis, the plaque buildup behind carotid stenosis, and to lower the chance of a clot forming. These are common steps recommended by the Society for Vascular Surgery:
- Aspirin or another medicine that makes blood less sticky.
- Medicines to lower cholesterol and blood pressure.
- Quitting smoking.
- A healthy diet and regular, gentle exercise such as walking.
Medical therapy continues even if you later have a procedure.
What Is the Treatment for 70 Percent Carotid Blockage?
A 70% or greater blockage is considered severe. Treatment depends mostly on whether you have had symptoms, along with your age, overall health, and surgical risk.
If You Have Had Symptoms
If a severe blockage has already caused a stroke, mini-stroke, or vision loss, a procedure to open or clear the artery is usually recommended for people who are healthy enough for it. The Society for Vascular Surgery recommends carotid endarterectomy as the first-line treatment for low-risk patients with symptoms and 50% to 99% narrowing (Journal of Vascular Surgery, 2021).
The main options are carotid endarterectomy, which removes the plaque through an incision in the neck, and TCAR, a less invasive way to place a stent. Before either one, your care team will review your medicines, and questions about taking Plavix before a carotid procedure are common.
If You Have No Symptoms
This is where recommendations are changing. The 2021 Society for Vascular Surgery guidelines recommend carotid endarterectomy as first-line treatment for low-risk patients with 70% to 99% narrowing and no symptoms.
In 2025, the large CREST-2 trial studied people with 70% or greater narrowing and no recent symptoms. It found that adding carotid stenting to intensive medical therapy lowered stroke risk compared with medical therapy alone, while adding endarterectomy did not show a significant extra benefit (New England Journal of Medicine, 2025). Ask your surgeon how these findings apply to the specific procedure recommended for you.
What this means for you: there is no single answer for a severe blockage without symptoms. Your vascular surgeon will weigh your stroke risk, procedure risk, and how well your risk factors are controlled before recommending medical therapy alone or a procedure.
Can Carotid Stenosis Get Worse Over Time?
It can. Plaque may keep building up, especially if risk factors like smoking, high cholesterol, or high blood pressure are not well controlled. That is why carotid stenosis is treated as a long-term condition that needs regular ultrasound checks. Your doctor will decide how often you need them based on your degree and health.
Tell your doctor right away if you notice any new symptoms between checks, even ones that go away quickly.
When Should You See a Vascular Surgeon in Houston?
See a vascular surgeon if an ultrasound showed 50% or more narrowing, if your degree has increased between scans, or if you have had any stroke-like symptoms. Call 911 for sudden weakness, numbness, speech trouble, face drooping, or vision loss.
Dr. Rema Malik is a triple board-certified vascular surgeon who treats carotid artery disease for patients across Sugar Land, Houston, and Tomball. You can learn more about vascular treatment in Houston or book an in-office consultation to review your results.
Frequently Asked Questions
Is 50% Carotid Blockage Bad?
A 50% blockage is moderate. It means plaque has built up enough to need attention, usually with medical therapy and regular checks. If it has caused symptoms like a mini-stroke, your doctor may recommend a procedure.
What Percentage Of Carotid Blockage Requires Surgery?
There is no single cutoff. Surgery is most often recommended for 50% to 99% narrowing that has caused symptoms. For 70% to 99% narrowing without symptoms, the choice depends on your health, your risk factors, and the latest evidence.
What Is The Difference Between Near Occlusion And Occlusion?
Near occlusion means the artery is almost completely closed, with only a thin stream of blood getting through. Occlusion means the artery is fully blocked and no blood flows through it. Both are evaluated case by case.
Do You Need A Ct Or Mri If Your Ultrasound Shows A Blockage?
Often, yes, if a procedure is being considered. Ultrasound can overestimate the degree of narrowing, so a CT angiogram or MR angiogram helps confirm the exact degree and shows the artery’s shape in more detail.
Sources
- Society for Vascular Surgery: Carotid Artery Disease
- Journal of Vascular Surgery: SVS clinical practice guidelines for extracranial cerebrovascular disease (2021)
- NEJM Journal Watch: Revascularization for asymptomatic carotid stenosis, the CREST-2 study (2025)
- Radiology: Carotid artery stenosis, gray-scale and Doppler US diagnosis, SRU consensus (2003)
- PMC: Review of NASCET and ECST methods for quantifying carotid stenosis
- PMC: Optimization of duplex velocity criteria for ICA stenosis, IAC report
