The warnings about deadly blood clots that start in the legs has gained widespread media attention in recent times. Travelers on flights are at a greater risk although this potentially fatal condition can strike even people who do not travel or board a plane. To a large extent, these conditions can be prevented and treated before it becomes deadly.
Meaning of DVT and PE
Deep vein thrombosis (abbreviated as DVT) refers to the formation of blood clots in the deep veins of the lower limbs or legs. The formation of blood clot in the deep veins of the legs can give rise to a variety of signs and symptoms such as swelling and pain in the legs. However, deep vein thrombosis is not considered a serious condition, unless the blood clot breaks away and reaches the upper regions of the body such as the heart and the lungs.
Read more to deep vein thrombosis.
Pulmonary embolism (abbreviated as PE) refers to a blockage in blood flow caused by a blood clot within the pulmonary artery. The pulmonary artery carries deoxygenated blood from the heart to the lungs for the purpose of oxygenation. Blockage of blood flow through the pulmonary artery is a very serious condition, and can lead to death within a short time.
How is PE linked to DVT?
Although deep vein thrombosis and pulmonary embolism are two different conditions, there is a causal link between the two. The blood clots responsible for most cases of pulmonary embolism are usually breakaway clots from the lower limbs that are affected by deep vein thrombosis. A dislodged blood clot from the lower limbs can travel to the heart via the bloodstream. As the right ventricle pumps blood into the pulmonary artery, the floating blood clot may clog the pulmonary artery, resulting is pulmonary embolism.
Signs and Symptoms
Blood clots within the deep veins of the lower limbs can give rise to a variety of signs and symptoms that are usually restricted to the affected limb region. The following are some of the signs and symptoms that may indicate the presence of deep vein thrombosis:
- Leg pain: Deep vein thrombosis usually causes pain in the affected leg. The pain is frequently localized to the calf muscle of the affected leg. In rare cases, the pain may also be felt in both the legs. In some instances, deep vein thrombosis may not elicit any pain at all.
- Tenderness in the leg: Tenderness in the affected region of the leg is usually present in deep vein thrombosis, regardless of the presence of pain. In some cases, tenderness may extend till the thigh region.
- Swelling in the leg: The lower part of the affected leg may exhibit swelling. In rare cases, swelling may be present in both the legs. Other signs of inflammation, such as redness and warmth may be present in the skin overlying the affected areas.
- Skin discoloration: In rare cases, the skin on the affected leg may become pale or exhibit a bluish discoloration.
Pulmonary embolism may cause the following signs and symptoms:
- Changes in breathing: Lack of oxygenated blood resulting from the blockage of pulmonary artery causes shortness of breath and rapid breathing. These breathing difficulties worsen with time.
- Chest pain: Chest pain is another symptom of pulmonary embolism. The pain may often be mistaken for a heart attack. Chest pain due to pulmonary embolism tends to worsen during coughing, deep breathing, eating, and physical exertion. Pain in the abdomen or the flanks may also accompany chest pain in some cases of pulmonary embolism.
- Cough: Pulmonary embolism may also result in productive cough. The sputum produced may contain blood. Wheezing may accompany coughing.
- Other symptoms: A variety of other non-specific signs and symptoms may also occur in pulmonary embolism. These include excessive sweating, fever, rapid heartbeats, lightheadedness, confusion and fainting. These signs and symptoms may not always be evident.
Due to the potentially lethal consequences of pulmonary embolism, it is important to seek medical attention immediately when symptoms of pulmonary embolism occur, especially in people affected by deep vein thrombosis.
Causes of DVT and PE
Deep vein thrombosis and pulmonary embolism are two different conditions. However, pulmonary embolism is frequently caused by dislodged blood clots that originate in the lower limbs. However, not all cases of pulmonary embolism are due to deep vein thrombosis.In rare cases, pulmonary embolism may occur even without pre-existing deep vein thrombosis. Deep vein thrombosis may exist for a long time, without causing pulmonary embolism.
Clot in the Legs
Deep vein thrombosis can affect individuals of any age group. However, it is more likely to occur in individuals who possess certain risk factors for deep vein thrombosis. These risk factors include old age (above sixty years), chronic bed rest, blood clotting disorders, hormonal disorders, obesity, smoking, and heart failure.
Blood clots can form in both superficial and deep veins of the lower limbs. However, blood clots in the deep veins of the legs are more likely to cause pulmonary embolism. The process of clot formation (technically referred to as thrombosis) is enhanced when the blood flow through the blood vessels is sluggish. Thrombosis mostly affects the lower limbs because of the tendency of the blood to pool in the lower limb compartments (due to gravity).
Activity of the calf muscles during walking and running helps in pushing the blood back towards the heart. Inactivity may cause sluggish blood circulation in the lower limbs, leading to enhanced risk of blood clot formation. Dysfunction of the valves in the blood vessels may also promote blood clot formation by contributing to the sluggish blood flow in the lower limbs. In some cases, the blood clot may dislodge and make its way to the heart and the lungs, ultimately resulting in pulmonary embolism.
Clot in the lungs
Most cases of pulmonary embolism are a consequence of deep vein thrombosis. The blood clot from the legs can travel to the heart through the bloodstream. The blood vessel that brings deoxygenated blood to the heart (known as the inferior vena cava) has a large diameter. Therefore, blood clots can pass through it freely. Blood clots can also pass freely through the wide chambers of the heart.
However, the pulmonary artery is not very wide, and blood clots can get stuck within this vessel, thereby blocking the flow of blood to the lungs. Sometimes pulmonary embolism may also be caused by other types of emboli, such as tumors, globules of fat, gas bubbles, and parts of medical equipment. However, blood clots (especially from the leg) are the most frequent cause of pulmonary embolism.