Carotid stenosis is a serious medical condition that is one of the leading causes of stroke or cerebral vascular accident (CVA). This condition usually develops without symptoms, and patients may remain asymptomatic until they experience a transient ischemic attack (TIA) “mini-stroke” or a larger stroke. In this two part series we will talk about carotid anatomy, detection/ screening guidelines. risk factors, additional diagnostic testing and treatment of this condition.
The carotid arteries
The carotid arteries (along with the vertebral arteries) bring blood to the brain. Plaque embolization (or flecks of plaque breaking off diseased or blocked arteries) is one of the main causes of embolic (or non-bleeding) strokes. In people with blockages in this artery, treating or removing the plaque can prevent stroke.
Today we will talk about screening and diagnosis. Next time: treatment options.
Detecting Carotid Stenosis:
These blockages can be detected with the use of a carotid doppler (or ultrasound) to listen to the speed of the blood (velocities) in the carotid artery and to visualize blockages. Some blockages can also be heard on physical exam – as a bruit (bru-ee) but this is not always a reliable indicator, as the most severe stenoses (or narrowing from plaque) usually don’t have a bruit.
Results are reported as a range and these results determine the next step and treatment options. Generally, in people that have NOT had a stroke surgical treatment is not advised until the blockage is 70- 80% blocked. This is because the risk of stroke increases with the amount of blockage, as the speed of the blood increases to pass through the narrowed space. (Picture a garden hose, now put your thumb over the end, covering most of it and make the water shoot out – that’s what we mean by increased velocity.)
If you have had a stroke or mini stroke from a plaque breaking off and travelling to the small vessels of the brain, the doctors will usually operate with lesser blockages because you have already demonstrated a tendency to have pieces break off, and the risk of having another stroke is higher than the risk of surgery.
Now this is important: strokes usually happen because of high grade (70 or higher stenosis) not occlusions (or 100% blockages). That’s because there is more than one vessel bringing blood to the brain ‘” (remember the vertebrals we mentioned earlier..) Doctors do not undo occlusions because that actually increases the risk of stroke at the time of surgery.
If you have an occlusion, consider yourself fortunate that you didn’t have a stroke when it was 99% and worry about keeping the remaining vessels as clean as possible with medicines.
Screening for Carotid Stenosis:
Currently there are no screening guidelines for asymptomatic individuals. Since symptomatic means the person has had a stroke or TIA (mini-stroke) knowing when to screen is important.
Generally screening should be done in people at high risk for developing accelerated plaque formation and in people with vasculopathic disease history (people with a history of plaque or blockages other places.)
High risk for accelerated plaques:
1. Diabetes: diabetes accelerates plaque formation, which is why new guidelines suggest ALL people with Diabetes, regardless of blood cholesterol tests should be on a statin drug (simvastatin, rosuvastatin, lovastatin, atorvastatin, pravastatin)* to help reduce plaque formation, even if their cholesterol levels on blood tests are normal. Reminder – cholesterol tests only measure cholesterol particles in the blood – it does not measure/ and can not measure the amount of cholesterol that is already adhering to blood vessel walls. So people with tight blockages who have been started on cholesterol medications may have normal cholesterol levels (because the medications are working.) We will talk more about the medications in part two. Just remember there is no “Drano” drug that melts away or removes blockages – the drugs available are used to prevent the condition from worsening.
2. History of smoking – smoking causes similar effects inside blood vessels as diabetes. As I explain to patients in the office, it makes plaque form faster by irritating blood vessels and making plaque more likely to stick. This is also important when we talk about ‘medical management’ of plaque diseases.
Note: ‘Medical Management’ is a term that means exactly that ‘” managing conditions (not curing or fixing) by use of medications. The disease won’t go away but the thought is that medicines will slow the worsening of the conditioning.
People with history of vasculopathic disease: these people should be screened because they already have a history of artery blockages ‘” but people don’t always realize that carotid arteries and other arteries are essentially the same highway, so to speak.
1. People with a history of Coronary artery disease (CAD) such as people with previous heart stents or bypass surgery. In fact, one-third of people screened for carotid artery while awaiting bypass surgery (also called CABG) have significant carotid disease or stenosis.
2. People with blockages elsewhere: Renal artery stenosis (kidneys), peripheral artery disease (PAD) aka blockages in the legs, mesenteric artery disease (abdomen).
3. People with an abnormal eye exam or Amarosis fugax : this is basically a small stroke or mini-stroke to the eye. Sometimes people develop symptoms (amarosis fugax – which is described as a sudden loss of vision, like a shade coming down over your eye). Other times, the ophthalmologist sees a plaque in the artery to the eye on exam.
In the second of these articles we will talk more about additional diagnostic testing once an ultrasound shows significant blockage, as well as the treatment options once carotid stenosis has been diagnosed.