What is DVT and PE?
DVT and PE are two separate conditions that may arise in the legs and lungs, respectively. DVT may cause PE. DVT stands for deep vein thrombosis and refers to blood clots that form in the deep veins of the legs. PE stands for pulmonary embolism which is a condition where the pulmonary artery to the lung is blocked by a blocked clot. Most of the time the clot in PE starts in the leg (DVT) and breaks off from here to reach the lung.
Although DVT can cause a host of symptoms like leg pain and swelling, it is not usually seen as a serious condition unless the clot dislodges. PE on the other hand is very serious and can result in death within a short period of time. The clot in DVT can break away, travel up the legs to the torso and then enter the right side of the heart. From here the clot may pass through the heart and is then sent to the lungs where it can cause a deadly obstruction.
Causes of DVT and PE
In order to understand how PE is caused, it is important to first look at DVT. Even though PE is preceded by DVT, both are separate conditions. Therefore PE can arise without DVT but this is rare. Similarly DVT may be present for weeks and months without leading to PE but the risk still exists.
Starts in the Legs
Deep vein thrombosis (DVT) is more likely to occur in certain people and under certain circumstances. People who are over 60 years, have been restricted to prolonged bed rest, have a blood clotting disorder or hormonal disturbances, with heart failure, smoke or are obese are more likely to develop DVT. However, it can occur in any person of any age.
The term thrombosis means blood clot formation. In DVT, the blood clot form in the deep vein of the legs. Sometimes it can form in the superficial veins of the leg but this is less likely to lead to pulmonary embolism.This type of clot formation occurs when blood flow is slow (sluggish circulation). The leg is more frequently affected because of its distance from the heart and there is insufficient pressure to push it back up to the heart.
Movement of the legs allows for the blood to slowly make its ways back to the torso provided that the veins and its valves are functioning normally. When a blood clot forms here it may then remain in the leg for long periods of time and restricts the outflow of low oxygen blood back to the heart. Under certain circumstances this blood clot may then dislodge and travel up to the heart and then to the lung. This is then known as pulmonary embolism or PE.
Read more on deep vein thrombosis.
Stops at the Lungs
Pulmonary embolism (PE) is in most cases a consequence of deep vein thrombosis (DVT). Therefore people who are at risk of DVT are also at risk of PE. Blood from the legs veins enters the right side of the heart. This blood is low in oxygen and needs to be sent to the lungs where carbon dioxide is expelled and oxygen enters the bloodstream. From the right side of the heart, the blood is carried to the lungs through the pulmonary artery.
A blood clot from the leg may be able to travel through the bloodstream up to the heart with ease. The blood vessel to the heart (inferior vena cava) is large and the clot can move freely. It can then also easily pass through the heart (right atrium and then the right ventricle). However, the pulmonary artery is not as wide throughout its course and this is where the clot may then become lodged thereby leading to a pulmonary embolism (PE).
The term embolism means a blood clot that has formed elsewhere and is traveling through the bloodstream or has lodged elsewhere in the circulation. This should not be confused with thrombosis where the clot forms at the site and stays at the site. A thrombus becomes an embolus once it breaks away from where it was formed. While a blood clot is the most common type of embolus, fat globules, tumors, parts of medical equipment and even gas bubbles can be emboli.
However, in the majority of cases the blockage in pulmonary embolism is caused by a blood clot that forms in the legs (deep vein thrombosis).
Read more on pulmonary embolism.
Signs and Symptoms
It is important to note that if the DVT symptoms are followed by PE symptoms then immediate medical attention is necessary. Never delay with PE symptoms as the condition can lead to death.
- Pain in the legs usually in the calf on one side. In rare cases, the pain may occur on both side. Sometimes there is no pain.
- Tenderness is present in most cases even in instances where pain may not occur. The tenderness can extend up to the thigh.
- Swelling of the lower leg on the affected side. Both side swelling can occur but is rare. There may also be accompanying warmth or redness of the skin over the area where the clot is located.
- Pale to blue discoloration of the affected leg can occur in DVT but this is uncommon.
- Difficulty breathing that arises suddenly and is often accompanied by rapid breathing with the shortness of breath worsening over time.
- Chest pain that is often mistaken for a heart attack. It tends to worsen with exertion and even with eating, deep breathing and coughing. It may be accompanied by abdominal pain and/or flank pain.
- Cough that is productive and usually accompanied by wheezing. The expectorant may be blood-streaked or even gross bleeding.
A host of other symptoms may also be present in pulmonary embolism (PE) such as fever, lightheadedness, excessive sweating, rapid heartbeat, confusion and fainting. These other signs and symptoms may develop at different points in time during the course of pulmonary embolism and may at times not even be noticed.