How can surgery (carotid endarterectomy) help?

As we age, our arteries become stiffer and narrower, due to what is called atherosclerosis. There are many reasons why atherosclerosis develops, and positive changes in lifestyle can slow it down enormously. However, if it occurs in the carotid arteries, which supply the brain, the narrowing that arises increases the risk of a stroke. This narrowing is called carotid stenosis, and it can be measured quite easily.

Sometimes the narrowing of the carotid artery causes symptoms that resemble those of a stroke, but are temporary, lasting only a few minutes. This is known as a transient ischemic attack - or TIA - which is really a mini-stroke. The symptoms are:

• Sudden numbness or weakness of the face, arm or leg, especially on one side of the body
• Sudden difficulty seeing with one eye or both
• Sudden confusion, trouble speaking or understanding
• Sudden trouble walking, dizziness, loss of balance or coordination
• Sudden severe headache with no known cause

If someone has had TIA symptoms or even a mild stroke, and there is over 50% narrowing of the carotid artery, a surgical procedure called carotid endarterectomy is highly advisable, to prevent a full-blown stroke. 'Cleaning-out' the artery in this way improves blood flow, without the risk of thrombosis giving rise to clots that then break off the wall and block an important brain artery.¹

Is age important?

Should everyone with carotid stenosis at risk of having a stroke undergo endarterectomy? Unfortunately, surgery in the very-old (i.e. the over 75's) is considered to be risky, although it's recognized that the risks are related more to existing illnesses, rather than to age itself. Recent reports of treating other diseases have shown this thinking to be wrong - the very-old fared as just as well as younger patients when given chemotherapy after surgical removal of colon cancer, and after cardiac bypass surgery for severe angina. Now Dr Peter Rothwell, of Oxford, UK, has analysed the benefits of carotid endarterectomy in different age groups, to see if advanced age is an obstacle to this surgery.

What the analysis shows

The analysis used pooled results two North American and European studies, as well as from some individual patients, using groups according to age: below 65 years, 65 to 74 years, and 75 years or above.

First, Dr Rothwell examined the risk of someone with troublesome carotid stenosis having a stroke in the next 5 years when treated by medication, rather than surgery. These patients all had more than 50% narrowing of the internal carotid artery. The results are given in the table:

Groups	Number of Patients	Number of Strokes	Risk (%)
Under 65 years	600	96	18
65 to 74 years	581	110	22
75 years and above	160	42	30
Total	1,341	248	21

As expected, the chances of having a stroke increased in the older age groups.

Next, the 'operative risk' of carotid endarterectomy was calculated. (This was the risk of stroke or death within 30 days in any patients having the surgery - it included patients with any narrowing, not just those with more than 50%.)

Groups	Number of Patients	Number of Serious Events	Risk (%)
Under 65 years	1,685	116	7
65 to 74 years	1,346	89	7
75 years and above	296	17	6
Total	3,327	222	7

This showed that there was no increased operative risk of surgery in the very-old.

Using these numbers, the reduction with surgery of the 5-year risk of stroke or death in those with more than 50% narrowing, compared with medical treatment, was calculated:

Groups	No. of Events/No. of Patients: Surgical	No. of Events/No. of Patients:Medical	Risk Reduction (%)
Under 65 years	88 of 771	96 of 600	5.4
65 to 74 years	77 of 644	110 of 581	8.2
75 years and above	18 of 150	42 of 160	16.9
Total	183 of 1,565	248 of 1,341	8.0

Looking at the last column in this table, you can see that the average risk reduction with surgery for all the patients was 8%. However, in the over 75 patients it was almost 17%, the best result among the three age groups. In this age group, there was a higher risk of stroke without surgery (upper table), while there was no increased operative risk (middle table).

What this analysis means

Are these results valid for everyone at risk of stroke due to carotid artery narrowing? It seems likely, as the risks reported here correspond to those from other, large, community-based studies. This means that the conclusion - that there's a greater benefit from carotid endarterectomy in the very-old - is well-founded.

The next question is, should there be an upper age limit for this type of surgery? Should one stop at 90? It depends, of course, on the individual patient's condition. However, age, in itself, should not be a limit; the average life expectancy at age 85 (in the USA) is 6 years.

What's even more important is that future studies should include very-old people, provided it is safe to do so. Clinical studies are the most reliable way to find out if a new treatment is really beneficial or not in different groups of patients, especially different age groups. It's important in these studies to include sufficient very-old patients to allow conclusions to be drawn about the usefulness of different treatments in this growing population.