Just about anybody is at risk for a DVT, regardless of how well their blood clots or not. Some folks are just at higher risk, like smokers, women on oral contraceptives, Prolonged immobility, long leg fracture or other limbimmobilization, paralysis, varicose veins, and so forth. Also folks with hypercoaguable states too, but they’re only a small percentage.
Prior to starting anticoagulation, INR and PTT will be checked, I’m sure. Not to rule out coagulopathies, but just to assure that the baseline for monitoring the effectiveness of treatment is known.
If there are multiple recurrences, further evaluation could be done, looking in a number of different directions.
28% of DVTs occur in low risk healthy folks under the age of 40.
Thanks for a GOOD link to the video. I would not have expected a clot to travel that far and to be removed from the lung as easily as it appeared.
OTOH I am not an MD but closer to an engineer.
I had the left middle turbinate removed years ago and the MD INSISTED that only he could remove the packing. He pulled out slowly but a tickling in the nasal cavity resulted in a hemorage and the cavity had to be repacked for a couple of days. Next time I convinced him that if trouble developed I could stop immediately as by the time I conveyed any signal to him it would be too late. Removal proceeded in several steps to successful removal of packing and no bleeding. Sometimes MD’s are so impressed with themselves that they don’t realize there are some things the patient can do better than they ever could, e.g. removing packing without causing a hemmorage.
Ah yes, pulmonary emboli. One of my favorite causes of death since it is SO obvious at the autopsy table. I love pulling one of those suckers out of the main artery leading out of the heart. Whoop, look at that one!
It did NOT form in the lung at all. It formed entirely in the leg. Believe it or not. Hey, this is what I do when I’ve pulled a pulmonary embolus (PE to the cognoscenti) out of the mainstem pulmonary branch. I flip the corpse upside down and make a cut from the crease at the top of the thigh down to the ankle.
I divide the musculature, cavalierly and rapidly in the thigh since most of what I want is in Hunter’s canal and is deep buried, fairly rapidly in the calf since it’ll be right up against the septum between the tibia and fibula, very carefully in the popliteal cavity (space behind the knee) since it’ll hump up right to the surface in one unpredictable spot. I look for the deep venous system. (Reassurance to the worried: clots in blood vessels just under the skin do NOT cause death. Varices, those ugly looking swirls of visible veins just under the surface, do NOT cause death. Only clots in the deep venous system ever cause death.)
The sciatic nerve comes burrowing up from one side of the meaty thigh and the femoral vein comes down from the other. They meet a few inches at most above the popliteal fossa and from there they accompany eachother. Vein, artery, nerve, in a bundle. Little tiny vein branches run from the deep venous system through the big muscles of your calf to the superficial veins. (These little branches are not big enough to carry blood clots that can kill you.) These branches are called perforating veins, because they perforate through the red muscle tissue. When I am dividing the gastrocnemius and soleus muscles to get down to the deep, deep, deep venous system, if this is the leg where the clot started, I find clots in the perforating veins. They look like little dark red sausages popping out of the transected veins. When I see those, I say, oh boy, I’m on the right track.
Get down to the deep vein and boy howdy, it’s swollen and distended with a sausage of thick blood clot from the ankle up to… the collapse point. The collapse point is the point in the vein where the sausage broke free that went to the lungs and killed the victim. The vein is all distended and unhappy up to the collapse point, then it looks collapsed. It has liquid blood in it from that point on up to the heart.
Get this. I can measure the blood clot I have pulled out of the pulmonary artery. I have to pull it out in pieces and uncoil it, since it coils up as it heads down into the lungs where it gets stuck, much as toilet paper may coil as it rushes down the plumbing. I frequently measure eight, ten, twelve inches of clot. Winner is eighteen.
I then go down to the collapse point (if I found it - not always lucky enough to find it) and measure from there up. Sometimes these fourteen-inch clots have run all the way from the back of the knee to the top of the thigh. When they broke loose, it was a couple of heartbeats’ time for them to progress with the wave of blood, like a Viking ship riding the tide to inevitable destruction, up the ever increasing diameter of the inferior vena cava, through the roomy right atrium and roomer right ventricle, through the still-large pulmonary artery, by sheer chance into either the right or the left mainstem pulmonary artery branches (sometimes by bad luck into both), try to go down the ever narrowing diameter of the pulmonary artery branches into the lung, coil, get stopped, plug up.
This is known as a “massive pulmonary embolism” (only kind that comes to me - I start when they’re dead, remember) and it is easily as long as the one you saw pulled out of the guy’s chest.
There’s a reason for this, and a very decent reason for your skepticism. Fresh clots to not have a consistency where they could be pulled out like this. Fresh clots, if you’ve ever handled them, are stretchy, and break up easily once you pull them past their stretchy point (“elastic and friable” to the trade). They would be very difficult to pull out in one piece.
But. When the clot starts to form in the deep vein in your calf, the vein that’s up against the gristle membrane between the two bones of your leg, the body tries to get rid of it. The body tries to get rid of it by growing little microscopic fibroblasts into the clot from the edges inward. The fibroblasts migrate out of the wall of the vein (I think - open to correction here, QtM, KarlGauss). They create tiny microscopic capillaries. Following the capillaries, scar tissue. At the same time the lining of the vein, which is made up of cells, tries to grow across the surface of the clot, making a clear space for blood to flow past it. Eventually you get a small clot at one side of the vein with endothelial cells coating the surface, and scar tissue growing in from the outside edge. Long after this, there will be a small crescent-shaped bump in the wall of the vein, scar tissue under the bump, normal vein lining over the bump. I see those sometimes in the leg veins of people who have developed new clots and died from them.
The clots seem to me to break loose oftenest when they have just begun to settle into fibrin layers and maybe have a few fibroblasts just beginning to grown into the outer edges. That is, when they’re a few days to a week old. They are stable enough to come off all of a piece, and they stay all of a piece as they float on the tide up through the heart and into the lung. That’s why you can pull them out like the doc did.
Clots that have a lot of capillaries and scar tissue growing into them from the wall of the vein are less likely to break loose, and clots imprisoned under a shiny new layer of endothelium are not going anywhere.
to be continued
I love Virchow’s triad. I teach it to the medical students as: what 3 things make you likelier to get a blood clot in your leg when you are sitting in coach all scrunched up on a 5 hour airplane flight?
Clottier blood
Slower blood flow
Something wrong with the smooth wall of the vein.
What gives you clottier blood? Cancer. Cancer is a big one. Not sure why - KarlGauss, does anyone know? – but if you have cancer, you are at a much higher risk for blood clots. When my beloved nana (may she rest in peace) was living with the cancer that eventually killed her, one day she developed a pain in the side of her chest. It was a worrisome pain, it made her put her hand over it. It bothered her a lot when she was breathing deep, but also when she breathed shallow. I tried massaging the spot over it, but the massage didn’t help. I said, “Nana, maybe you need to relax.” She shot me a look and said, “Honey, I am relaxed.”
Her doctor said maybe it was emphysema and prescribed her an inhaler. Later, when we found out it was a small blood clot that had broken off from her leg and reached her lung, killing about 10% of one of her lungs, he felt so ashamed of himself. So did I, and I was only a medical student.
Neither of us ever thought to ask: does she have an increased breathing rate and increased heart rate without stimulation? Simple vital signs would have done so much towards the diagnosis.
They put her on heparin and she was fine. She also could’ve had a Greenfield filter put in. Maybe I better leave the explanation of the Greenfield filter to Qadgop the Mercotan.
OK, ‘cause I have the teensiest bit of hypochondria (and want to live to be 112), what helps one avoid clots? Does staying in shape help? Are heavy weight folks or those who dont’ exercise at higher risks? If you do find yourself imobilized with a broken leg, is there anything you can do to prevent a clot from forming?
[QUOTE=gabriela]
I love Virchow’s triad. I teach it to the medical students as: what 3 things make you likelier to get a blood clot in your leg when you are sitting in coach all scrunched up on a 5 hour airplane flight?[\QUOTE]
Clottier blood
Slower blood flow
Something wrong with the smooth wall of the vein.
Aren’t y’all sorry you asked me to weigh in on this topic.
Slower blood flow. Naturally the blood flow in your vein is not going to stop. But it can slow weigh down. What are some of the things that slow it?
Well, position can. Classic forensic example - the chronic alcoholic who falls asleep drunk with his legs crossed. In his stupor he doesn’t turn from side to side in his sleep. He develops blood clots after several hours in the calf of the leg that’s compressed by the other leg.
Or the other classic forensic example, 8 months pregnant woman who just can’t keep herself from sleeping on her back. 2000 gram fetus plus amniotic fluid plus pregnant uterus lying on the inferior vena cava. Blood still gets through, but it has to push its way past the compression site; it’s slowed. Blood clots develop in the calf veins, which is where the end of the line is, where the blood flow is slowest.
I have autopsied a woman who had huge fibroids of her uterus, and who slept on her back. Same result. QtM, her uterus plus leiomyomata weighed 1400+ grams.
I also autopsied a man who broke his humerus and was given a sling while awaiting definitive treatment (never did understand the hospital part of the story - why not cast it or rod it right away?). It hurt so much he went to sleep sitting up for three nights in a row. Bam, three days later, dead from a PE. The collapse point was at his inguinal ligament - that is, the damn thing formed in his thigh vein, not his calf vein, because he was sleeping folded forward over his leg to keep the arm out of pain.
That’s also what happens when people get DVTs from long airplane trips. Position.
to be continued if people are not so bored they just leave the SDMB
Blood is so inherently clotty that it clots if it touches smooth glass. It clots if it touches collagen. It clots if it touches meat. It clots if it touches any surface except the surface of the inside of a vein, coated with endothelial cells. Endothelial cells are not only super smooth (covered with compounds that keep blood from clotting) but they are little factories that continually secrete substances that prevent clotting. Unless you rip a hole through them, of course, and then they intentionally release substances that cause clotting. Smart.
How do you get something wrong with the smooth wall of a vein? Interrupt it. Like stick a knife through it. Even though it heals, it will never heal quite as smooth as it was before it was stabbed. A knife blade’s not the best example, though: if you survive it and heal, that thin line of scar tissue in the vein wall, overlaid by endothelium, is so tiny and so insignificant it will almost never cause new clots to form over it.
Shrapnel, on the other hand. A guy who’s ever had shrapnel through his calf, he is forever at risk for forming deep leg vein clots. He should not go on long distance flights without chewing aspirin and walking up and down the cabin every fifteen minutes. Flex his leg muscles all the time he can’t get up, too. I do this on long flights.
What’s the single commonest precursor to clots forming in a leg vein? Clots that previously formed in the same leg vein. You remember they heal with a bump of scar tissue in the wall with a layer of smooth endothelium over it. The blood eddies around the bump. There’s a little protected backwater just in front of it, even if it’s small. If there is ever a situation again in which the blood is unusually clotty, or the blood flow gets slowed down (say a long plane ride), then that’s where the clot will form.
And once they form, they propagate.
Both directions. Up and down the leg.
And once they propagate, they can break away and kill you.
Gabriela, boring the Straight Dope since April 2006
Dear Tremorviolet, with the usual cautions about this is not medical advice, seek an experienced practitioner, one cannot diagnose over the Internet, and if you need me for your doctor you are in a seriously bad condition, here’s the answer:
Avoiding clots: keep your blood flowing (fidget if you sit sedentary, don’t maintain folded over positions of your thighs and legs, don’t sleep on your back), don’t let your blood get clotty (be tested for the gene MTHFR and Protein C and S deficiency and whatever the gene of the day is that predisposes people under 40 to blood clots; take half an aspirin every day; don’t get pregnant or get cancer), don’t get problems with the smooth walls of your veins (no shrapnel. And no clots).
Yes, staying in shape helps.
Yes, being heavy puts you at higher risk. Consult your regular practitioner for advice on how much risk and what your other medical conditions are that may interact.
Yes, ask Qadgop the Mercotan for better advice. Commit a crime if necessary to get his personal attention.
Me, I treat everything the same way.
With a Y-shaped incision.
Please don’t stop Gabriela. This is fascinating. I’m a nuclear medicine tech so I get to image these things once they’ve hit the lungs sometimes and it’s so cool to have a deeper understanding of them.
The clot travels in the veins to the heart. From there it goes to the lungs. Depending on how big it is, it will lodge in the smallest vessel it can fit in. If that vessel feeds blood to 10% of one of the lungs, than that 10% loses it’s bllod supply and is effectively “dead”. Now 10% doesn’t sound like much, but when it happens that suddenly, than the effects can be very uncomfortable.
If, however, the clot is large enough to lodge in the main pulmonary artery, than all blood stops going to the lungs. This stops all pulmonay gas exchange. You have about as long as you can hold your breath to live.
The size of the embolized clot determines how much pulmonary function is lost. If that % lost is small enough, you may live long enough to get to an OR and have it removed or have thrombolitics (clot busters) injected into your blood stream to hopefully break up enough of the clot to allow for more pulmonary function.
The clot blocks blood flow out from the right side of the heart. So, no blood gets sent through the lungs back into the left side of the heart. Since it’s the left side of the heart that supplies blood to rest of the body, it means your brain, your heart muscle itself, and everything else in the body gets no blood supply. Absence of blood flow to the brain will cause unconsciousness almost instanteously and, of course, death very shortly thereafter.
I work in a radiology clinic, so I quite frequently see reports of these babies getting inserted.
The primary reason they are inserted is because of confirmed or suspected DVT in the lower extremities: the filter is placed in the inferior vena cava to prevent such a clot from reaching the lung, as the IVC is en route from the lower extremities to the lungs.
It is often inserted as an intracatheter procedure, where the radiologist accesses the vascular system through the femoral vein or the internal jugular vein, and is done usually for patients for whom anti-coagulants are contraindicated.
And… and… it’s probably really gross and slimy and icky when they do it. (Sorry, my contribution wasn’t as interesting as gabriela’s.
Happened to me at a quite healthy age 28 - shattered my left tibia and fibula just above the ankle while on oral contraceptives, which was followed by some mighty prolonged immobility, 4 hours of surgery, including open reduction and internal fixation and the installation of a lovely Ilizarov device, and as one might imagine, some more rather prolonged immobility.
I was in the hospital for a week plus, then was evaluated at home by a physical therapist the day after I was released. I mentioned my knee was a bit sore, which was odd as I hadn’t injured the knee. On a hunch she called my surgeon, who had me go back to the hospital for a venous ultrasound. The physical therapist may have saved my life - there was a honkin’ huge deep vein thrombosis next to my hip joint, and they readmitted me on the spot and put me on IV anticoagulants for a few days, and Coumadin for months afterward. (Made sense in restrospect; my leg had been elevated, so the left hip was the lowest point on my body basically for 2 weeks.)
If you read the patient insert in a package of birth control pills, it says to stop using them if you are going to be bedridden or immobilized for an extended period. Sadly, I wasn’t given the opportunity to do that before I broke my leg.
Just how big can a clot be before its a problem? The reason I ask is that I work for a medical device company (shall remain nameless) that makes devices to go in venous circulation. While we do thrombogenicity tests on our devices and certainly don’t want them to accumulate thrombus, we tend not to be too concerned about thrombus on the venous side. Our clinical guys have told me that your lungs catch small clots all the time.
Now, the arterial side of things is a whole 'nother story. We’re very concerned there. But usually what ends up being done is giving the patient heparin for those procedures and regularly flushing our devices with heparinized saline.
Anything in the venous system larger than a red blood cell will obstruct some level of flow to the lungs.
The branches of arteries to the lungs (pulmonary arteries) from the heart start off rather large; about 1.5 to 2cm in diameter (about as big around as a US nickel). As these approach the lungs they start to start to split into smaller and smaller branches.
Think an 8 lane highway forking into two 4 lane hwy’s, than each of those splitting into 2 lane hwy’s, than to single lanes. If a group of cars starts off in the 8 lane and everybody stays in their lane, then you end up with cars being forced into 8 single lanes all lined up neat and pretty.
Each time a bifurcation (medical term for one vessel splitting into two) occurs there is a reduction in diameter. The ultimate goal (like the cars in single lanes) is for these vessels to get smaller and smaller so that all of the red blood cells end up in a vessel so small that there is only enough room for the RBCs to fit in a single file line. This allows for gas exchange (bad out, good in hopefully).
If anything is in that flow to the lungs, it will be forced through the same channels. If it is smaller than a RBC, than it will simply pass through and not cause problems. If it, however, is larger than a RBC, than it will go through the channels of smaller and smaller diameter vessels until it reaches a point that it gets stuck. All flow stops past this point. Now, if this obstruction is only a few times the size of a RBC, than the relative amount of pulmonary function lost will be minimal and not noticed. But, it is as large as one of the larger vessels, than it will block off a larger portion of the flow to the lungs.
I think is very irresponsible for a company to take the stance that any clotting in the venous system is trivial. When something the size of a marble floating around in the venous system could kill you with little or no warning, that is always something to take into consideration.
First, this was not official company policy (as I stated, we have a lot of biocompatibility tests to do on our devices, including thrombogenicity). This was a conversation I had with one of our clinical people and was his opinion only. I also think we’re thinking different sizes. The size of a marble is much larger than what I was thinking–more like a flake a millimeter or two in its largest dimension. What are the consequences to blocking off a pulmonary arteriole?
