I just read an interesting story about a new treatment for occlusive strokes.
The device is known as Penumbra and is being put out by the company of the same name Penumbra, Inc.
From the story I read, and from my brief visit to the company website, it looks like it might have promise to treat some stroke victims who otherwise would be sort of out of luck.
Basically, from the description, this is a catheter type device that is threaded into the femoral artery (The great big artery in your groin that feeds blood to your leg), and is worked in retrograde fashion up the aorta and then into the appropriate arteries (carotid, etc.) until reaching the site of the blocked artery inside the skull. It then acts basically like a vacuum cleaner and sucks out the blood clot that is blocking the artery and causing the stroke.
So a little background on strokes is in order.
There are basically two main types of strokes, Occlusive and Hemorrhagic.
The names are pretty descriptive.
In an occlusive stroke, an artery feeding a particular part of the brain is occluded, cutting off blood flow to that part of the brain. This is almost always caused by a blood clot forming in the artery at the site of a ruptured plaque (due to arteriosclerosis…i.e. “hardening of the arteries”), or forming somewhere “upstream” from the site of the blockage (in the heart or a larger artery), breaking off and then floating downstream until it gets to a small enough artery to get stuck and block it. (I say “almost always” above, because there are some much less common causes that I won’t go into in this post.)
With hemorrhagic stroke, an artery feeding some part of the brain actually ruptures and blood begins to leak out into the surrounding brain tissue. This is also frequently a result of arteriosclerosis.
A major contributor to arteriosclerosis is smoking. If you are a smoker, did you see my last post urging you to quit? If not, go look at it, and then QUIT SMOKING!
The particular symptoms one experiences from the stroke, such as facial drooping, or weakness on one side of the body, etc, are dependent upon which area of the brain is being affected.
Anyway, the first type of strokes described, the occlusive strokes are the ones this device is aimed at.
Currently, the main emergency room (E.R.) treatment for these strokes involves the use of a clot-buster medication called tPA (which stands for Tissue Plasminogen Activator). This stuff is given intravenously and can dissolve a blood clot.
Sounds great right? Well, it’s actually not so great.
There is a big list of contraindications for giving tPA. This stuff is not without risk of serious complications. The main one being undesirable bleeding. The first thing on the list is the one which keeps the vast majority of patients with occlusive stroke from receiving tPA and that is time from onset of symptoms. If tPA is going to be used, it must be given within a maximum of 3 hours from the first onset of stroke symptoms.
During my 3 years of residency training, I saw a LOT of folks come into the ER with occlusive strokes. I, and the rest of my colleagues in training were always itching for the opportunity to use tPA in a stroke patient. On average only about 3-5% of folks with stroke actually make it to the E.R. in time to be a candidate for tPA. Of all the stroke victims I saw, only one…that’s right, only one in 3 years time….actually arrived at the E.R., within 3 hours of symptom onset. Unfortunately, this patient also didn’t get tPA because she got excluded by one of the other exclusion criteria on the aforementioned big list.
So, there’s two messages here.
The first and most important one is IF YOU START HAVING ANY SYMPTOMS THAT MIGHT BE A STROKE, GET YOUR BUTT TO THE E.R. IMMEDIATELY!!! Don’t sit around the house like Cleopatra (the Queen of De-Nile) hoping it’ll just go away on it’s own. CALL 911 RIGHT AWAY!
The second message is that the first message is largely ignored, and even when it ain’t ignored there’s often other criteria preventing the use of tPA, so maybe that stuff ain’t so great after all.
Here’s where it appears Penumbra may come into the picture to make things a little better. Penumbra has a somewhat longer time-frame within which it can be used. Unlike tPA which has to be used within 3 hours of symptom onset, Penumbra has an 8 hour window.
It seems obvious to me that the device gets it’s name from the concept of the “Ischemic Penumbra“, which in a nutshell is the area of brain tissue that is not getting adequate blood flow due to the occlusive stroke, but which hasn’t actually died yet…i.e. the area of brain tissue this device aims to save.
Remember however, the name is Penumbra, not Panacea.
While an 8 hour window is obviously better than the 3 hour window tPA has, I suspect there will still be a heck of a lot of folks who won’t get to the E.R. in time. Certainly though, the numbers should still be better than with the tPA timeframe.
There’s also the issue of problems associated with reperfusion. In the world of medicine, it’s nearly impossible to find any treatment for any condition that doesn’t at least have the potential to make things worse, and Penumbra is no exception.
When you cut off the blood flow to an area of tissue for any appreciable length of time, there is serious potential for a condition known as reperfusion injury to occur if blood flow is restored. (Warning, if you follow that link, it’ll take you to an article that uses a lot of twenty-five dollar words and may make your eyes glaze over. It’s a pretty interesting read however if you can stand the medical jargon). Basically reperfusion injury is a pretty complex inflammatory type of process that in a nutshell can cause further cell death. So, by restoring blood flow, there is the potential to actually kill more brain tissue. That eye-glazing article talks about some current research trying to prevent that.
The other big potential problem associated with removing the clot has to do with the structural integrity or durability of the artery wall. If you’ve got an artery that is compromised by long-standing arteriorsclerosis, it is at increased risk of tearing open when blood pressure is restored to it. Further, just like the brain tissue that has been starved of blood flow, the walls of that artery are also composed of cells that have been potentially injured by the lack of nutrients and oxygen due to the clot upstream. As a result, the arterial wall is now potentially quite weak and prone to failure.
So what happens if the arterial wall ruptures? Well, at that point, your occlusive stroke has just evolved into a hemorrhagic stroke.
So, as the msnbc article discusses, Penumbra sounds like its got a lot of potential to serve as one more tool in the E.R. toolbox, but it is not without some potential pitfalls.
So, here’s the two questions that immediately popped into my head when I read about Penumbra.
1. Has the company looked at all into using this or a similar device for treatment of occluded arteries elsewhere in the body, such as for treatment of blocked coronary arteries in heart attacks for instance?
2. When a person suffers a hemorrhagic stroke, one of the main complications that can occur is that the growing pool of blood that is pumping out of the ruptured artery and into the surrounding brain tissue can cause tremendous pressure to build up inside the skull. This pressure can do great harm to the soft and fragile brain tissue. Often times, such a condition results in a trip to the operating room where a really smart fella known as a neurosurgeon ends up cutting a hole in the skull (known as a craniotomy) to relieve the pressure and remove the pool of blood. Does Penumbra have any potential to be used in hemorrhagic strokes to suction this pool of blood out from the inside, rather than the patient having to undergo craniotomy?
I know this is a pretty new blog, without a lot of exposure yet, but it is indexed on Google and Yahoo. Perhaps somebody from Penumbra, Inc. will run across it and can leave some comments.
I’d appreciate it, as I suspect the other readers would as well
How ’bout it folks?