Medical Musings: High Blood Pressure and Strokes

We were reading a report, written in 2012 about the National High Blood Pressure Education Program (NHBPEP) of the National Heart Lung and Blood Institute (no comma used in their name, apparently.) 2012 was the 40th anniversary of this initiative and the paper noted that when it was started only about a quarter of the people they surveyed knew there was a connection between high blood pressure and heart disease and stroke, and most people were not being treated. After 40 years 90% of people knew about the connection and most of those surveyed were being treated for hypertension or monitoring their blood pressure. Not coincidentally, the age adjusted mortality rate for heart disease and stroke had fallen by 70% and 80% respectively over this time—although other factors such as the reduction in smoking over this time undoubtedly played a big role in this.

But we still think most of those educated people are picturing stroke in hypertension wrongly. (As do many medical professionals.) You see, many people will picture this as being a situation like an overinflated balloon or bicycle tire—the pressure builds and then the balloon, or blood vessel bursts.

But most of the time it’s not like that.

To see how hypertension really causes strokes, you first have to know that strokes are divided up into ones with little or no bleeding outside the blood vessel and those were there is bleeding into the brain. (We call this condition in the brain strokes, but yes, you can get this situation in other parts of the body as well.) The majority of strokes are not bleeds instead they are blockages—the infract or occlusion. The damage from this kind of stroke comes from the blood vessel in question being blocked, so the brain tissue it supplies is starved of oxygen and nutrients and dies.

Now there are also two kinds of infracts. The “embolic stroke” describes a situation where a clot from somewhere else travels to the head and gets stuck in a brain vessel. Usually this happens in “a-fib” or atrial fibrillation. In atrial fibrillation the heart does not beat strongly enough to keep blood from clotting up in the heart’s nooks and crannies—until it does, giving an extra-strong beat or briefly going back into a regular rhythm. Then, unfortunately, it spits out a clot (these are not hard scabs, but more jelly-like clumps, like clots from heavy menses) which typically heads right up the neck artery and into the brain where it can eventually get caught in a vessel too small to get through. This is why people with atrial fibrillation are placed on medications to reduce the blood’s clotting ability and why they need to be very conscientious in taking them.

What’s the deal with high blood pressure then?

Well, the other kind of infract is when the clotting seems to form in place, right there in the blood vessel. This is actually where hypertension comes in. High blood pressure damages the lining of the blood vessels making it much easier for the contents of the pipeline to stick to the walls. Next thing you know you’ve got a mess in there, like a clogged up drain pipe, or debris backing up on a snag in a river, with much worse consequences, since it’s happening in your head rather than your yard.

So if you were picturing your blood vessels popping like balloons (sure it can happen, but that’s another story) you should reset your image maker.

Bonus fact. Did you know that up until about 50 years ago many doctors didn’t even want to treat high blood pressure? They thought it was just a side effect of heart disease and treating it wouldn’t help anything so what would be the point?