Signs and symptoms of a blood clot depend upon the situation, the amount of bleeding, and the location of the blood clot. Many times, the clot itself may cause no symptoms until it embolizes and becomes lodged in small blood vessels at distant sites in the body. The effects of the lack of blood supply to an affected organ will determine the symptoms.
Blood flows through the body in a continuous loop. Blood is pumped through the body by the heart, but that same blood returns back to the heart both by gravity and by the muscles of the arms and legs contracting and squeezing, or milking, the blood back to the heart. If blood becomes stagnant, it may clot and cause potential life-threatening conditions.
The medical term for a blood clot is a thrombus (plural: thrombi). An embolus refers to the situation in which the clot breaks away from its original location and travels through the bloodstream to another location.
There are four potential outcomes regarding a blood clot. It will either
Blood clots that increase in size or embolize may cause limb (arm, leg) or life threatening conditions.
Blood is supposed to clot to help repair a blood vessel that is injured. Clots or thrombi become a problem when they form inappropriately. There are a variety of illnesses and risk factors that can lead to blood clot formation.
Atrial fibrillation describes a heart rhythm disorder in which the upper chamber of the heart does not beat in a coordinated fashion. Instead of having a single electrical impulse that allows the atrium to contract, hundreds of electrical impulses are generated, and the atrium jiggles like a bowl of Jell-O. This may cause small blood clots to form along the lining of the atrium. The potential exists for these clots to break away and embolize to other parts of the body, causing diseases such as stroke or ischemic bowel (loss of blood supply to part of the intestine).
Deep vein thrombosis (DVT) is the term used to describe clots that form in the veins of the arms, legs, or major veins in the pelvis. Risk factors for DVT include:
Immobility may include recent surgery or hospitalization. This is especially a concern when surgery on a leg is involved or the extremity may be immobilized in a cast or splint. It also includes patients who undergo hip and knee replacement. Muscle movement in the extremity may be decreased, and this lack of motion increases the risk of blood clot formation. Prolonged airplane and automobile trips similarly minimize movement. Blood tends to pool by gravity in the lowest parts of the body. Without standing and walking at regular intervals, blood is not returned easily back to the heart by muscle contraction, and blood clots may form.
Blood clots may form acutely in an artery that has been gradually narrowed by plaque in vessels affected by arteriosclerosis. Plaque is a collection of cholesterol, calcium, fibrin and cell waste products that can form, grow and gradually narrow an artery. If the plaque ruptures, it may initiate the clotting cascade, and a newly formed clot can completely block an artery. The risk factors for arterial clot are those commonly associated with heart attack, peripheral vascular disease, and stroke.
These include:
When bleeding occurs outside an artery or vein the blood tends to pool and clot. Passing blood clots in the urine, the vagina, or in the stool is very frightening and should not be ignored. There may be a significant problem, or the bleeding may be easily explained. For example, bleeding is commonly seen with bladder infections or hemorrhoids.
Bleeding or blood clots in the urine should not be ignored and presumed to be "just a bladder infection." The bleeding may arise from a bladder tumor or irritation of the bladder lining from other reasons (for example, cancer radiation therapy), or it may originate in the kidneys because of kidney stones or cancer. Sometimes, if there is enough bleeding, clots will form in the bladder and may pass in the urine. This is commonly seen in older male patients with enlarged prostate glands that may cause difficulty with urination.
Blood in the stool or rectal bleeding is never normal and should always be investigated. While hemorrhoids or anal fissures may be the source, bleeding may also be due to a variety of other illnesses including tumors, or cancer, inflammatory bowel disease, infections, and diverticular bowel disease. Again, if there is enough bleeding present, blood clots may form and be passed as part of a bowel movement. Passing blood clots from the vagina happens almost routinely in menstruation. If blood from the uterus pools in the vaginal area, blood clots of varying sizes may form. However, vaginal bleeding during pregnancy is never normal and medical advice should always be accessed if this occurs, either by telephone or in person.
Usually the signs and symptoms of a blood clot will be enough to alert and potentially alarm a patient or their family enough to seek care.
An arterial clot prevents blood rich with oxygen and nutrients from getting to cells, causing them to stop functioning. This usually causes a true emergency and emergency services should be activated (often by calling 911).
Many different health-care professionals may be involved in caring for a person with a blood clot depending on where the clot is, and the patient's medical situation. Specialists that treat blood clots include emergency room doctors; primary health-care professionals including family medicine; internal medicine; women's health professionals; cardiologists; neurologists; pulmonologists; vascular surgeons; hematologists; interventional radiologists; and hospitalists.
The first step in making the diagnosis of a blood clot is obtaining a history from the patient for family. Patients rarely are able to make their own diagnosis of a blood clot so the health-care professional will need to ask questions about what might be happening. If a blood clot or thrombus is a consideration, the history may expand to access the patient's risk factors or situations that might have put the patient at risk for forming a clot.
Physical examination will help add information to increase the suspicion for a blood clot.
Testing will depend on the suspected location of the blood clot.
Computerized tomography (CT) is often the test of choice when suspicion of pulmonary embolus is high. Contrast is injected intravenously, and the radiologist can determine whether a clot is present.
On occasion, ventilation perfusion (V/Q) scans are performed to look for pulmonary emboli. This test uses labeled chemicals to identify inhaled air into the lungs and match it with blood flow in the arteries. This test is less accurate than a CT scan and is subjective to variances in interpretation.
Should a pulmonary embolus be diagnosed, the amount of clot and potential severity of the disease may require further testing. Echocardiogram is an ultrasound of the heart that may be used to decide how much strain the blood clot in the lung is causing on the heart.
Arterial thrombosis is an emergency, since tissue cannot survive very long without blood supply before there is irreversible damage. In an arm or leg, often a surgeon is immediately consulted. Arteriography may be considered. Arteriography is a technique in which dye is injected into the artery in question to look for blockage. Sometimes, if there is a large artery that is occluded, this test is done in the operating room with the presumption that a surgical procedure will be necessary to open the vessel and restore blood flow.
For an acute heart attack, the EKG may confirm the diagnosis, although blood tests also may be used to look for enzymes (troponin) that leak into the bloodstream from irritated heart muscle. With an acute heart attack, the diagnostic and therapeutic procedure of choice is a heart catheterization. A catheter is placed into the coronary artery, the blockage identified and a stent placed to restore blood supply to heart muscle.
Other variations of head CT may be considered to look at blood flow in the brain (perfusion CT) or the arteries themselves (CT angiogram).
For an acute stroke (cerebrovascular accident, CVA), the test of choice is a computerized tomography (CT) scan of the head to look for bleeding or tumor as the cause of stroke symptoms. If the stroke symptoms resolve, meaning that a transient ischemic attack (TIA) has occurred, tests may include carotid ultrasound to look for blockage in the major arteries of the neck and echocardiography to look for blood clots in the heart that may embolize to the brain.
Depending upon their location, blood clots may be aggressively treated or may need nothing more than symptomatic care.
Venous thrombosis in the leg may occur in the superficial or deep systems of veins.
Clots in the superficial system are often treated symptomatically with warm compresses and acetaminophen or ibuprofen since there is no risk for clots in the superficial veins to embolize to the lung. They are connected to the deep system by perforator veins that have valves that act like a sieve to strain and prevent clots from traveling to the lung.
Deep venous thrombosis usually requires anticoagulation to prevent the clot from growing and causing a pulmonary embolus. Treatment tends to occur in an outpatient setting using medications that anticoagulate or "thin" the blood. There are a variety of medications available to treat blood clots.
Blood clots below the knee are at lower risk for embolization to the lung, and an alternative to anti-coagulation treatment is serial ultrasound examinations to monitor the clot to see whether it is stable or growing.
Pulmonary emboli are treated similarly to deep venous thrombosis. In patients who have increasing shortness of breath or weakness, hospitalization may be required during the initial treatment phase. In certain situations, when there are large amounts of blood clot in the pulmonary arteries, strain can be put on the heart and lung function and thrombolytic therapy with tissue plasminogen activator (tPA) drugs, so-called clot busting drugs, might be considered. These patients are usually critically ill and in shock.
Arterial blood clots are often managed more aggressively. Surgery may be attempted to remove the clot, or medication may be administered directly into the clot to try to dissolve it. Alteplase (Activase, tPA) or tenecteplase (TNKase) are examples of clot busting medications that may be used in peripheral arteries to try to restore blood supply.
Heart attack: The same approach for heart attack is used as for arterial blood clots. If possible, cardiac catheterization is performed to locate the blocked blood vessel and a balloon is used to open it, restore blood flow, and a stent is placed to keep it open. This is a time-sensitive procedure and if a local hospital is unable to perform a heart catheterization emergently, within 60-90 minutes of the patient's arrival to medical care, thrombolytic medications described above like tPA or TNK may be used intravenously to try to dissolve the thrombus and minimize heart muscle damage. There will still be the need to eventually transfer the patient when stable to a hospital with the capability to perform heart catheterizations.
Stroke also is treated with tPA if the patient is an appropriate candidate for this treatment. Each patient is different and may or may not qualify for this medication with an acute stroke. Again, this is a time sensitive emergency and in addition to tPA, an interventional radiologist may be able to insert a catheter into the blood vessels of the brain, identify the clot and remove it, thus hopefully reversing the stroke.
The treatment of blood clots often is directed at interfering with the normal clotting mechanism of the body. Different medications may be used to block specific factors in the clotting cascade and are chosen based upon the disease or illness being treated and other underlying medical issues that are present in the individual patient. Some of the medications prevent additional or future blood clots while others can help dissolve existing blood clots.
Aspirin is commonly used to decrease platelet function (platelets are important in helping clot formation) in the treatment of heart attack and stroke. Other anti-platelet drugs include clopidogrel (Plavix), prasugrel (Effient), ticagrelor (Brillanta), ticlopidine (Ticlid) and aspirin and dipyridamole (Aggrenox).
Warfarin (Coumadin) acts as a blood thinner by blocking clotting factors (II, VII, IX and X) that depend upon vitamin K. Every patient is unique when it comes to the dosing requirements for warfarin (Coumadin), and repeat blood tests are routinely done to make certain that the blood is anti-coagulated to the appropriate level. There are numerous drug interactions with this medication that can cause the blood to become "too thin" such as some antibiotics. Warfarin (Coumadin) dosing always needs to be monitored by a healthcare professional, and a patient should never alter the dose of this medication without consulting with their healthcare professional.
Factor Xa inhibitor medications have been approved for the treatment of certain types of atrial fibrillation, deep venous thrombosis and pulmonary embolism. They begin working almost immediately and do not need blood tests to monitor their activity. Medications in this class of anticoagulants include apixaban (Eliquis), rivaroxaban (Xarelto), and edoxaban (Savaysa). Dabigatran (Pradaxa) also is an alternative anticoagulation medication that is a direct thrombin inhibitor. As opposed to warfarin, which can have its anticoagulation activity reversed, at present there is no reversal agent available in the United States for Factor Xa and thrombin inhibitor medications. These medications also may be used to help prevent blood clots in the leg after hip and knee replacement surgery.
Heparin works by inactivating thrombin and factor X. It is an injectable medication available for use intravenously or as a low molecular weight medication called enoxaparin (Lovenox) or fondaparinux (Arixtra), which can be injected subcutaneously (under the skin). Heparin is often used routinely as part of the heart attack treatment protocol. Because of its rapid onset of action it is often the first medication started once a blood clot is diagnosed in the hospital.
Tissue plasminogen activator (tPA or TNK) may be used to dissolve blood clots that are life-threatening and are most often used for clots that occlude arteries in situations such as stroke or heart attack; there are occasional instances in which the drug is used for major vein obstruction. The medication can be injected into an intravenous line that has been started in a vein of the arm, or it may be dripped directly into the clot. This requires specialized critical care technology and physician skill to thread a catheter to the site of blockage to deliver the clot-busting medication. Decisions regarding the use of this drug are individualized for the specific patient and situation.
Recognizing that a potential illness may exist associated with a blood clot is the first step in getting treatment. Since many of these illnesses are life-threatening (heart attack, stroke, pulmonary embolus, ischemic bowel), accessing emergency care and calling 911 may be the most important step in treatment.
Depending upon the underlying disease, surgery may be required to remove a blood clot. Often this occurs emergently in life- or limb-threatening situations in which anti-coagulation with heparin or the use of thrombolytic medications is not appropriate or when these have failed to resolve the blood clot.
There are many patients who don't know that they have had a blood clot in their leg, either because the symptoms were mild, or those symptoms were ignored. Up to 25% of patients with a pulmonary embolus die from sudden death.
For those patients with a provoked deep vein thrombosis, one where the cause is known and is temporary, there is a small risk of future bloods clot once the initial anticoagulation treatment is complete.
For patients who have an unprovoked DVT or PE or who have active cancer or a blood clotting disorder that makes their blood more likely to clot, lifelong anticoagulation may be required. Guidelines suggest that this decision be revisited every year.
For all patients, the patient and the health-care professional need to balance the benefit of anticoagulation against the complication risk of bleeding. The doctor will try to match the blood thinning drug with the patient's situation, to minimize that risk of bleeding.
Prevention is always the key in medicine. This is especially true when it comes to many of the diseases associated with blood clots.
Symptoms of a blood clot in the leg (deep vein thrombosis or DVT) occurs when a clot clogs the blood flow in a vein, causing inflammation. Examples of symptoms and signs of a DVT in a leg are: