Pulmonary Embolism

We have often heard that that brain and heart clots are extremely dangerous. However, we know little about the dangers of PulmonaryEmbolism, i.e. clots in the lungs. This article will talk about causes, symptoms, diagnoses and treatment of PulmonaryEmbolism. Before speaking about the actual issue, we shall speak about how the clot is formed and track its route to the lungs. Let us first understand blood circulation.

Blood Circulation

There are two systems of blood circulations in the body: the main circulation that transfers the oxygenated blood from the left side of the heart to the arteries; and consecutively to the tissues and cells that render oxygen and expel carbon dioxide. After this, the other circulation i.e. pulmonary circulation starts. In this process, the non-oxygenated blood transfers from the left side of the heart to the lungs. Lungs in turn, hold on to the oxygen and exhale carbon dioxide. Then the blood returns to the left side of the heart in order to start the main circulation.

The clot formation begins at the veins of the legs and thighs and is caused due to various reasons - one of which is the deep vein thrombosis of the leg. The clot travels through the system of the body, until it arrives on the right side of the heart. It is then pumped from the right ventricle to the pulmonary circulation and reaches the lungs, thereby blocking the arteries fully or partly. This changes the body’s physiology, causing critical side effects, like the disability of the lung to oxidize the blood, which leads to a lack of oxygen in the blood level. Blocking a vital part of the pulmonary circulation, leads to shortage in the blood volume;and when transferred to the left side of the heart can lead to a sharp decline in the blood pressure and even a cardiac shock.



How does it deteriorate?

There are some medical conditions that aid the probability of clots in the leg, thus causing strokes. Lung diseases like autoimmune diseases or shortage of anti-clotting material in the body, increase the risk of clotting, however it is rare. In most cases the cause of the clots are the other diseases that affect the ability of the blood to clot; for example, an orthopedic surgery of the joints of the lower limbs. (Surgery of the thigh bone or replacing Hip joint or pelvis)

The risk of blood clotting is increased during pregnancy and after birth, due to weight gain and lack of movement. Heart weaknesses, obesity, and brain clots are the other causes of pulmonary embolism.

Passengers travelling for long hours by road or air are advised to move their limbs regularly during travel to avoid clotting.



Symptoms of pulmonary embolism differ according to the size of the clot, the functioning of the heart and the lung capacity. Shortness of breath is considered the most important and familiar symptom. It may be accompanied by other symptom like chest pain, cough, dizziness, and palpitation. The patient may also cough blood. In the critical cases, there may be a deficiency in the level of oxygen in the blood and the patient may go into cardiac shock leading to a sudden death.

The infection rate is evaluated per 1000 people. In the U.S., 500-600 thousand people are affected every year and around 1000 of them go into cardiac shock leading to death in the first hour. As mentioned above, the symptoms of lung clot are not easily identified or diagnosed as they are similar to other symptoms of respiratory and circulatory disease. So the patient may have several complications. In a study involving the patients at the Intensive Care Unit at the King Khalid University Hospital, it was concluded that the death rate of pulmonary embolism is about 14% and is higher in older people who are infected by brain clots and nerves disorders. The most dangerous elements are surgical operations and obesity.



If there is even a slightest doubt, appropriate tests and correct diagnosis should be done. The patient’s chest x-rays, blood gas analysis and pumping of the heart, help the physician diagnose better. To ensure accuracy, x-ray tests should be done with radiation of digital class or nuclear radiation, and the lungs should be tests for perfusion and ventilation.




If there is a doubt, the patient is given intravenous or under the skin sluices of blood for several days. After the disease is affirmed the patient must be given sluices of blood through the mouth (Warfarin). Once the blood liquidity level via Warfarin is acceptable, intravenous sluices of blood are stopped, but the patient has to undergo Warfarin for 6 more months.

During the treatment, the patient should be periodical checked to monitor the blood liquidity level. The patients who have sluices of blood should consult the physician before taking newer medicines, as some medicine increase the level of sluices of blood and other decrease its level, both can cause dangerous complications.

In the case of a cardiac shock, medicines for clot-busting or dissolving clot are prescribed along with regular medicines. However, it causes bleeding in some patients. Surgical intervention may be required when there is no response to this type of medication. If the patient responds to the medicine, the heart and lung functions will return to its normal course in a few months.



Ahmed BaHammam, FACP, FCCP
Professor of Medicine
Director, University Sleep Disorders Center
College ofMedicine, King Saud University