Blood Clots (cont.)

What are the risk factors for blood clots?

The risk factors for arterial clots are those that are common to all diseases that cause narrowing of blood vessels. They include:

•high blood pressure,


•high cholesterol levels,


•diabetes,


•smoking, and


•family history.
Venous clots are formed due to one of two main reasons.

1.Most commonly, when the body stops moving, the risk of blood clots increases, since the lack of muscle movement allows blood to become stagnant in veins.


•This typically may occur when a person is hospitalized or bedridden after illness or surgery.


•It may also occur with long trips either in a car or a plane where hours may pass without a person getting up to walk or stretch.


•Orthopedic injuries and casting also put the patient at risk.


•Pregnancy is a risk factor for forming blood clots in the legs and pelvis, since the growing uterus may slow blood flow back to the heart to a sufficient extent that blood clots may form.
2.There may be a genetic or inborn error in the clotting mechanism, making a person hypercoagulable (hyper=more + coagulation= clotting) and at greater risk for forming clots.

What types of conditions are caused by blood clots?

Blood clots may cause life-threatening medical conditions, and for that reason are foremost in the mind of health care practitioners when it comes to diagnosis and prevention.

Deep venous thrombosis and pulmonary embolism

Deep venous thrombosis may lead to a pulmonary embolism, a condition in which the clot breaks off in a leg vein, travels in the veins back to the heart, and is pumped out of the heart through the pulmonary artery to the lungs with blood to be oxygenated in the lungs. In the lungs, the blood clot becomes lodged in the small blood vessels of the lung.

An embolus is the medical term for a blood clot that has moved with the bloodstream to a different location. With pulmonary embolus (pulmonary embolism), two issues occur.

1.The lungs' blood supply is comprised and the affected area of lung tissue may infarct, or die.


2.Because of the blockage, the ability of the lung to provide oxygen to the body is decreased and hypoxia (decreased levels of oxygen in the blood and throughout the body) may occur.
Even if venous blood clots do not embolize, they may cause significant local issues with swelling and pain. Since blood cannot return to the heart if a vein is blocked by a clot, the limbs may chronically swell and have decreased function in a condition called chronic thrombophlebitis.

Arterial thrombus

An arterial thrombus stops the blood supply to the tissues beyond the blockage, depriving cells of oxygen and nutrients. This quickly leads to tissue death. Arterial thrombus is the mechanism that causes:

•heart attack (when it occurs in the coronary arteries that supply the heart)


•stroke (when it occurs in arteries within the brain), and


•peripheral vascular disease (occurring in the arteries of the legs).
Atrial fibrillation

In atrial fibrillation, small clots may form along the walls of the atrium or the upper chambers of the heart. Should one of these clots break off, if can embolize, or travel in the bloodstream to the brain, blocking an artery and causing a stroke. Other arteries may also be involved by this process, including those that supply the bowel. This can cause mesenteric ischemia (mesentery=lining of the bowel + ischemia=loss of blood supply) and potential necrosis (tissue death) of the intestine.

Blood should clot anytime it becomes stagnant. This also means that clots will form when blood leaks out of blood vessels.

Examples include some of the following:

•With bleeding peptic ulcers, patients may vomit liquid blood mixed with clot.


•Patients with rectal bleeding may also have clot mixed with the bloody stool if there has been time for the clot to form.


•Sometimes patients with urinary tract or bladder infections develop associated bleeding in their urine, and small clots can form. On occasion these clots may be so big that they cannot be passed and block the urethra, preventing urination and causing urinary retention.


•Vaginal bleeding is a normal event for most women in the reproductive years and occasionally, blood can pool in the vagina and form clots before being expelled. If clots form in the uterus, they may cause significant pain and pressure as they pass through the cervix while being expelled