My dad is currently facing the possibility of carotid artery surgery, and it’s gotten me curious about some things. Not seeking medical advice, just looking to understand what goes on inside the body.
In his particular case, he has a carotid artery that is 70% stenosed (I think that’s on one side; not sure about the other), and his doctor wants to operate to remove the material that has built up there. Not being very experienced with vascular disease myself, 70% stenosis sounds scary high.
Questions:
-How can a person continue to function normally with blood flow to the brain so severely restricted? In the studies I’ve been reading, some of the patients are presenting with stenoses as high as 80% or 90%. Is there really that much excess flow capacity in unrestricted set of carotid arteries?
-If the carotid arteries have so much plaque built up in them, doesn’t that mean there’s a similar amount of plaque built up throughout the rest of the body? If not, then why does it particularly tend to accumulate in the carotid arteries?
-Is the hazard associated with high-grade stenosis that some of this plaque will break off and cause localized strokes in the brain, or is it that the 70% stenosis of the carotid could suddenly become 100% stenosis right there in the carotid?
-Do some people have a greater tendency for plaque to break free and circulate to cause arterial embolisms? In other words, if you have two patients with a comparable degree of stenosis, is it possible for one of them to have little bits of it constantly breaking off and causing embolisms elsewhere in the body, while the other patient remains completely healthy, with plaque staying put wherever it has built up?
-Why do we commonly hear about arterial embolisms causing heart attacks and strokes, but we rarely hear about them causing problems elsewhere in the body? Yes, sometimes we hear about pulmonary embolisms and DVT in the legs, but those seem relatively rare compared to heart attacks and strokes. Why aren’t PE’s/DVT as common as heart attacks and strokes?
Lots of questions. I don’t have a lot of time just now, but will start:
There is usually collateral flow through other vessels. Also, even with 70 or 80% stenosis, the flow is still (usually) more than adequate.
Yes, in general. But, different vascular beds behave differently in different people. As a general rule, though, carotid disease comes later than coronary. There are exceptions.
Most of the time, it’s the former - crud breaks off and travels downstream until it plugs a smaller artery. This is a good example of how different arteries behave differently, though. For the coronary arteries of the heart, the more common development is that a 70% suddenly becomes 100% due to a clot forming at the narrowed site (say, because of some inflammation or bleeding there). Despite being more common in the coronaries, this can also happen in the carotids. And, don’t forget that junk often breaks off an atherosclerotic aorta and may then go the brain where it causes a stroke. The aortic arch is a common site for this to happen.
A huge area of research - the biology or pathobiology of the plaque.
In fact, people often get arterial embolisms to various parts of their body in the condition called atrial fibrillation (where clot often forms in the upper chamber of the heart - the left atrium - then travels out to the brain, gut, foot, arm, . . .). And, nothing to do with atrial fibrillation, plaque often breaks of the aorta - the major artery coming from the heart - and goes to the feet, kidneys, etc.
Thanks for your answers; much appreciated. You said you didn’t have much time, implying that these answers might have been more brief than you’d like; any elaboration or addition you can provide would be most welcome.
Regarding the uniformity of plaque buildup throughout the vascular system…I have read elsewhere that arterial plaque tends to accumulate at bends and junctions in arteries (presumably where there is a great deal of turbulence and flow stagnation), and that this is why there is particular focus on the carotid artery as a way to reduce the risk of stroke: it’s a big vessel with major junctions right there in the neck. Is that accurate?