GETTYSBURG MEDICAL NEWS
THE CLINICAL VIEW
By: Phillip E. Hoffsten, M.D.
23, September 2000

BLOOD CLOTS IN THE LUNGS

A very common but often misunderstood problem is called pulmonary embolism. Embolism means a blood clot broken off some place in the body and then carried to another place where it lodges causing problems. To have a blood clot form in the lungs primarily is very, very rare. I have never seen this in my 40 years of medical practice. Instead, what happens is blood clots form in the legs or in the pelvis. After they grow large enough, a piece of a clot breaks loose and then is carried through the very large veins in the legs and into the even larger inferior vena cava carrying blood back to the heart. The blood clot will wash right on through the heart and then go into the large arteries delivering blood to the lungs. But now, the blood vessels in the lungs get smaller and smaller as blood is carried out to the individual air sacs with little tiny blood vessels. As the blood vessels get smaller and smaller in the lungs, finally the blood clot is so big it can go no further and it blocks the blood supply to a portion of the lungs.

Lungs are surprisingly forgiving. One-third of the blood supply to the lungs can be blocked with no real impairment of the body’s function. Somehow, the remainder of the lung circulation bed dilates and makes up for the stopped up blood vessels. However, after more than one-third of the blood supply has been blocked, shortness of breath and fatigue begins to occur. If a single very large clot were to come along and block one whole lung, this still may not be fatal; although the person would have substantial symptoms of fatigue and shortness of breath and perhaps chest pain with that.

Once the diagnosis is made, there are several treatment options on how to take care of this condition. Most commonly a medication called Heparin is used by injection. This medication keeps the blood from clotting normally and allows the blood clots that have formed time to melt. An interesting point is that if blood clots are left alone in the body, they will dissolve by themselves over the course of several days. Thus, if a medication used to slow down blood clotting can be used, the clots that are present will melt away by themselves.

Usually, at the same time that Heparin is started, another medication called Coumadin is begun at the same time. Coumadin works by slowing the rate at which clotting factors are made and thereby there are fewer clotting factors around to form blood clots.

Very rarely when blood clots are forming too fast and in too large of a number, a filter has to be placed in the large vein returning to the heart from the legs.

One other way to take care of blood clots to the lungs is to melt them with a medicine called Streptokinase. When a person’s circulation is significantly compromised and their heart is failing then the use of Streptokinase can very rapidly melt the blood clots that have already arrived in the lung. This may be a lifesaving step under the right circumstance. As always, no treatment is without side effect problems. The use of medications such as Heparin or Coumadin or Streptokinase can all result in abnormal bleeding independent of melting the blood clots in the lungs or the legs. The most common and devastating problem is when a stroke occurs due to bleeding into the brain. Thus, blood clots to the lung are dangerous if they are left alone and they are dangerous if they are treated. Trying to make the right decision on how to handle this type of problem requires a special level of alertness on the part of the health care providers and careful judgment on how to take care of the problem.

Finally, when more than one-half of the blood supply to the lungs is blocked, a mortal situation can develop.  Most commonly, the blood pressure will drop, the pulse becomes very fast, the person becomes very short of breath and chest pain just with breathing alone can become prominent.  If the blood clots happen to occur with the patient in their own home, it is finally at this point that medical  that medical attention will usually be sought.  This is a very dangerous time.

There are three common reasons why blood clots form in a person’s legs.  Then, when the person gets up and begins to walk after sitting for a long time, the clot can break loose and go to the lung.  Another common cause of blood clots forming in a person’s legs is injuries.  Bumps or bruises that injure the veins in the legs can lead to a small clot forming that then grows and becomes a major problem. The last common cause of the blood clots in the legs is called hypercoagulopathy.   Basically, this is what happens when the blood clots too easily.  In people who have heart problems and  the blood circulates too slowly, it will tend to form clots too easily.  Relatively unusually, a person can have a hereditary defect in which the blood clots too easily and this will lead to blood clots forming.

The most difficult part of dealing with blood clots in the legs that they break off and go to the lungs is making the diagnosis.  Somehow, the problem of pulmonary embolism is underdiagnosed because it is often very difficult to recognize.  Health care providers need to keep a high level of suspicion for this problem and then perform the appropriate tests to confirm the diagnosis.  Fortunately, there are now tests that can give a very accurate answer on the presence or absence of this problem.