Hundreds of thousands of people have undergone surgery or stents to “fix” blockages in their carotid arteries. (The left and right carotids are the main arteries to the brain.) Most of the these people (about 90%) reported no complaints. We say they are asymptomatic. The blockages were discovered on exam or by ultrasound of the neck.
The idea is that major blockages can progress to full blockages and cause stroke. Since it’s best to prevent stroke, patients with blockages get referred to surgeons and surgeons operate. The fix entails cleaning out the blockage, which we call endarterectomy. More recently, carotid stents (think cardiac stents, only bigger) have been used.
Sounds good, right?
It turns out that a look at the evidence in support of preventive carotid surgery is weak and outdated. (Note…There is no debate over intervention in patients with symptoms.)
Two trials, one done in the 1980s, the other in 1990s, showed surgery to have a slight superiority to medical treatment. Think about that for a moment. Medical therapy in the 1980s barely included statins. Yet, even against ancient medical therapy, surgery barely won.
Annually, the number of patients needed to treat (NNT) with surgery to prevent one stroke on the side of the blockage was 100. That means 99 out of 100 with carotid blockages have surgery without benefit. The problem, of course, is that surgery does not come free–the complication rate ranges from 2-3% in the best of hands. Real-world data shows it to be much higher.
If that sounds shaky, it gets worse.
Medical therapy has greatly improved over the past decades. We now have potent statin drugs, which have unquestioned benefit in patients with known vascular disease. (The argument with statins is their use in patients without disease–primary prevention.). We also have more advanced medical therapy for high blood pressure and diabetes. And most important, mainstream medicine now aggressively promotes smoking cessation. These advances in medical therapy are important because if carotid surgery barely beat 1980s-vintage medical therapy, it would not likely stand a chance now.
That my sound speculative, but recent studies support it. For instance, a group in Ontario Canada reported a 20-year experience of over 3500 patients, finding a tiny stroke rate with aggressive medical therapy. This group, and others, have shown that occlusion (yes, total occlusion) of a carotid rarely causes stroke. This is because the brain has ample collateral blood supply.
You see the problem: if modern-day stroke rates with medical therapy fall to very low levels, you can’t make them any lower with surgery–which comes with its own risk of stroke.
Another discovery I made was that the benefit of surgery looks gender-specific. When event rates in the trials were separated by sex, all of the benefit was seen in men. Event rates with surgery versus medicine were similar in women.
I think there are parallels here to cardiology. Namely, in the way we think about the disease atherosclerosis. In cardiology, we have long known that angioplasty, stents and even bypass surgery do not prevent heart attacks. These are focal solutions to a systemic problem. Focal treatments have their role–mostly in patients with symptoms.
I spent many days studying this evidence. I spoke to surgeons and neurologists. I wrote a review paper on it.