The Straight Dope

Go Back   Straight Dope Message Board > Main > General Questions

Reply
 
Thread Tools Display Modes
  #1  
Old 02-08-2007, 10:58 PM
Joey P Joey P is online now
Charter Member
 
Join Date: Jun 1999
Location: Milwaukee, WI
Posts: 21,402
How do blood clots kill?

I just heard that a truck driver that delivers to our business was undergoing a knee replacement surgery and died due to a blood clot.
We've all heard that blood clots can kill you if you throw one and it winds up in your lungs/brain/heart. My question is why?

Okay, I understand (more or less) what a blood clot is, and what it means to throw one. I also understand that after you throw a clot, it's going to travel through your veins until something stops it. Okay, if it lands in your heart it's going to cause a problem (it'll create a clog in that part of the heart, right?), that makes sense. In your brain, I can see why that would be a problem. It'll cut off blood flow to whatever part of the brain that vein feeds. But I've never understood why it's a problem if it lands on your lungs. I'm not saying it's going to do nothing. But your lungs are designed to maximize surface area right? So why does this little tiny clot cause such a big problem?
Reply With Quote
Advertisements  
  #2  
Old 02-08-2007, 11:17 PM
bouv bouv is offline
Guest
 
Join Date: Aug 2000
Quote:
Originally Posted by Joey P
So why does this little tiny clot cause such a big problem?
Because, relative to the size of the tiny capillaries that feed the lungs, the clot is huge, and can have the potential to block off large portions of the lungs.
Reply With Quote
  #3  
Old 02-08-2007, 11:20 PM
Evil Joe Evil Joe is offline
Guest
 
Join Date: Jan 2007
Here is some good info about it, Wiki didn't really discuss what was happening physiologically.

http://www.emedicinehealth.com/pulmo...article_em.htm
Reply With Quote
  #4  
Old 02-08-2007, 11:40 PM
KarlGauss KarlGauss is online now
Out of the slimy mud of words
Charter Member
 
Join Date: Mar 2000
Location: Between pole and tropic
Posts: 6,884
How do blood clots kill

I assume you're mostly asking about clots in the lungs. They can kill for two (and sometimes, three) reasons:

It's possible that the clot will block the blood flow into the lungs (out from the right side of the heart). If this happens to such a degree that there's inadequate blood making it into and then through the lungs, and then out into the left side of the heart, then the blood pressure will fall to the point that the brain and other vital organs don't get enough blood supply*.

Another possibility is that the lungs themselves can be so damaged by the clot(s), that they can no longer get enough oxygen into the circulation.

Rarely, if a person has a hole in their heart, then a clot from the legs CAN cross over from the right side into the left side of the heart. This avoids the lungs, but the clot might then go to the brain (which is probably worse). This is called a "paradoxical embolus".

(* at the risk of being patronizing, I should confirm that you're familiar with the normal route of blood circulation in the body, i.e.:
blood coming back from the body ==> veins ==> right heart ==> lungs ==> left heart ==> arteries ==> blood to the body)

Last edited by KarlGauss; 02-08-2007 at 11:44 PM..
Reply With Quote
  #5  
Old 02-09-2007, 08:11 PM
t-bonham@scc.net t-bonham@scc.net is online now
Guest
 
Join Date: Mar 2003
Quote:
Originally Posted by Joey P
Okay, if it lands in your heart it's going to cause a problem (it'll create a clog in that part of the heart, right?)
Actually, it's pretty rare for a clot to hang up inside the heart itself. The aorta is the largest blood vessel in the body, and the heart itself is beating, so blood is not very likely to get caught there. Where it can get caught is in the cardiac arteries, that feed the heart muscle itself. These are much smaller, and can get blocked by a clot. Then the heart muscle is starved, and stops working. That is called 'cardiac arrest', or a 'heart attack'. Which is very serious, often fatal.

It's not a clot inside the heart itself, but in the cardiac arteries, mostly outside, around the heart, where it causes a problem.
Reply With Quote
  #6  
Old 02-09-2007, 08:54 PM
Qadgop the Mercotan Qadgop the Mercotan is online now
Charter Member
 
Join Date: Apr 2000
Location: Slithering on the hull
Posts: 22,294
Quote:
Originally Posted by t-bonham@scc.net
Actually, it's pretty rare for a clot to hang up inside the heart itself.
I'd hardly call it rare. I've seen plenty of patients with intramural thrombi in the atria, and somewhat less often the ventricles, with debris thrown out the aorta to cause strokes or other embolic phenomena.

KarlGauss, I remember being taught in med school that often a large embolus could also kill via vagal stimulation, causing severe bradycardia and hypotension. Still the theory?
Reply With Quote
  #7  
Old 02-09-2007, 09:50 PM
brossa brossa is offline
Guest
 
Join Date: Feb 2005
Quote:
Originally Posted by t-bonham@scc.net
Actually, it's pretty rare for a clot to hang up inside the heart itself. The aorta is the largest blood vessel in the body, and the heart itself is beating, so blood is not very likely to get caught there. Where it can get caught is in the cardiac arteries, that feed the heart muscle itself. These are much smaller, and can get blocked by a clot. Then the heart muscle is starved, and stops working. That is called 'cardiac arrest', or a 'heart attack'. Which is very serious, often fatal.

It's not a clot inside the heart itself, but in the cardiac arteries, mostly outside, around the heart, where it causes a problem.
If a sizeable chunk of clot has broken off a clot in the veins of the legs or vena cava, it will go through the right side of the heart first and then out one of the pulmonary arteries to the lungs. If the clot is large enough, it can block bloodflow to an entire lung, or even hang up very close to the heart and block flow to both lungs at the same time.

The capillary bed of the lungs is a supremely efficient filter, and basically no clot can make its way through the lungs and back to the left side of the heart, barring significant lung abnormalities. The aorta comes off the left side of the heart, and the coronary arteries are small branches off of the very first part of the aorta. The sort of heart attack that t-bonham describes is called a coronary embolism, and is a rare entity that usually occurs in someone with in whom a clot has formed de novo in the left side of the heart. This could be due to an abnormal heart rhythm, diseased valves, or previously damaged heart muscle. Most heart attacks are not caused by this mechanism, but by clots forming in the coronary arteries at sites of chronic damage to the blood vessel wall.
Reply With Quote
  #8  
Old 02-10-2007, 02:21 AM
picunurse picunurse is offline
Member
 
Join Date: Mar 2003
Location: Seattle
Posts: 11,427
Quote:
Originally Posted by t-bonham@scc.net
Actually, it's pretty rare for a clot to hang up inside the heart itself. The aorta is the largest blood vessel in the body, and the heart itself is beating, so blood is not very likely to get caught there. Where it can get caught is in the cardiac arteries, that feed the heart muscle itself. These are much smaller, and can get blocked by a clot. Then the heart muscle is starved, and stops working. That is called 'cardiac arrest', or a 'heart attack'. Which is very serious, often fatal.

It's not a clot inside the heart itself, but in the cardiac arteries, mostly outside, around the heart, where it causes a problem.
(My bold) Those would be the coronary arteries.
Reply With Quote
Reply



Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 06:53 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright 2013 Sun-Times Media, LLC.