Carotid stenting sounds like a wonderful solution to the layperson. But the truth is always more complicated. I’ll talk about it more here to give a better understanding of the disease, diagnosis, and treatment options.
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 this decides 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.
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 – count yourself as lucky 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)*
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.
So your doctor (or nurse practitioner / physician assistant) ordered a carotid ultrasound, now what?
The ultrasound – carotid duplex
This is a great screening tool – to screen if you have blockages or not. It doesn’t hurt, there is very little risk, it’s fairly quick and can be done almost everywhere. (Really – sometimes you can get carotid ultrasounds at the mall during health screenings..)
If the results show carotid stenosis or elevated velocities suggesting stenosis of 70% or better – it’s decision time. Now some test interpretations are a bit complicated – a lot of tests rate stenosis using ranges, and my least favorite range is 60-79% because it’s such a wide range at a point where 70-79% means possible surgical treatment yet 60-69% doesn’t.
** Some of my more proactive patients ask about surgery for lesser stenosis – such as 60% or even 40% – this really isn’t practical for a couple of reasons:
1. a 60% may stay at that level of disease (particularly with medications) for a very long time
2. The risk of stroke with this level of stenosis is much, much less than once a person crosses the 70-80% barrier, so the risk from surgery/ stenting may outweigh the risk of ‘watchful waiting’. While surgical risk is low (we will talk about this later – it’s not zero – so taking additional risks when the stenosis is not severe is unwise.)
Additional Diagnostic Tests:
At this point it’s time to make a few preliminary decisions; if you absolutely do not want surgery – don’t bother with the additional tests. We can prescribe medications using the information from the Ultrasound..
But – if you haven’t ruled out surgery – The CTA or MRA are essential! These tests are more accurate – which is important for those people with ‘shoulder’ results (the 60-79% category).
These tests also give surgeons a road map to work from.
1. CTA 0r computerized tomography (CT scan) with angiography:
Most surgeons that I have worked with prefer the CTA over the MRA for surgical planning. It’s less expensive, and the imaging is excellent for vascular structures. Now a CTA includes contrast dye – usually in amounts that equal or exceed a cardiac cath (about 100ml) so people with kidney disease or risk for kidney complications either receive prophylaxis or an MRA.
At a previous position, I developed CTA protocols to prevent contrast-induced kidney damage using criteria set forth by the international radiology community.
Special Procedure Orders
This helped protect people at higher risk for complications – after all you shouldn’t develop problems from a test used to detect other problems.. But it made the test an all day procedure, so the patients could receive IV fluids and other medications.
According to the international radiology guidelines, the following individuals are at higher risk of developing complications:
– age greater than 75 – elevated BUN/Creatinine (kidney labs)*
-hx of chemotherapy/ radiation – diabetes
-solitary kidney -known kidney disease/ previous failure
– organ transplant hx -several other conditions (see protocol)
*usually creatinine greater than 1.2
I have attached the form for interested readers.
2. MRA – magnetic resonance angiography
this test is based on a MRI which gives much greater detail of soft tissue structures (not particularly needed for vascular surgery but good for other diagnoses). This test uses a different dye which is less toxic to people with bad kidneys. (However, if there is severe kidney disease or on dialysis – this dye has it’s own risks of complications. For patients on dialysis, CTA is generally preferred – and the test is done the day before the regularly scheduled dialysis day.)
After the tests confirm that both: 1.) the stenosis is as severe as previously estimated on ultrasound and 2.) the blockage is somewhere we can reach either surgically or in the lab –
It’s time to talk about treatment options.
Treatment options include: (and risk of stroke with each)
1. Do nothing (it’s always an option) – but for a blockage of 70-80% the risk of stroke is about 15% or 1 in 6. This climbs to 25% for people with a history of stroke or TIAs. Since I don’t have a crystal ball – I can’t tell people who will be that 1 in six.
2. Medical Management (aka medications) – medications are actually reasonable effective for many people. Clopidogrel, ASA 81mg, and a statin drug are the usual drugs prescribed. People with heart history should already be on most, if not all of these. This has been reported in the literature to bring risk of stroke down to 8%.
(Of course, this is assuming that people actually take them regularly – and surprisingly, most people don’t/ won’t.) The cost of the clopidogrel (plavix) is sometimes an issue for people, it is quite pricey. There are statins available on the $4 formulary. It’s also not a great choice for people with bleeding problems – previous bleeding strokes, bleeding ulcers or a history of falls.
3. Carotid Endartarectomy (CEA) – surgery to clean out the artery. This requires a trip to the operating room, and often an overnight stay. Surgery is actually fairly safe (we’ll discuss more at next post) even for the very elderly (proven safe for people in middle and late 90s in several studies. Surgery brings the risk of stroke down to about 1% (it’s slightly less than one percent but I rounded up to a full percent). This risk of stroke is basically centered around the time of surgery (during surgery and first thirty days after).
4. Carotid Stenting – this option was heralded (by the people doing it) as the second coming, and stents were placed in LOTS of people for flimsy reasons “patient refused surgery” (not mentioning that they scared the poop out of patients over surgery) yet research has failed to confirm the safety or efficacy of the procedure with the rate of stroke ranging from 7% to a full FIFTEEN percent in some studies. (Now remember, for many people – fifteen percent means they should have just stayed home/ picked option one.) Now the interventionalists (the doctors who perform this procedure) are in big doo – doo because they have been misleading patients for several years, or overplaying (vastly) the risks and fears of surgery and downplaying the risks with stents..