Pulmonary Embolism

Introduction

Blood circulation within the body involves two distinct cycles or circuits. The first and shorter of the two is known as the pulmonary cycle. This is followed by the systemic cycle.

Deoxygenated blood collected by veins from all parts of the body is finally returned to the right side of the heart. The pulmonary cycle begins when the right ventricle of the heart pumps this venous blood into the lungs by means of the pulmonary artery. This is done so that the deoxygenated blood can again be refreshed with oxygen received from the alveoli of the lungs. When this is done, oxygenated blood from the lungs now travels to the left side of the heart. This completes the pulmonary circuit.

Oxygenated blood is now pumped by the left ventricle of the heart into the aorta which distributes it to all parts of the body through the arterial system and capillaries. Deoxygenated blood is then collected by veins and brought back to the right side of the heart once again. This second phase is known as systemic circulation.

What Is Thromboembolism?

The efficiency of blood circulation is dependent on the smooth and unobstructed flow of blood through arteries, veins, and capillaries. Oftentimes, our arteries become clogged with the deposition of a cholesterol plaque. This can make it difficult for blood to flow through. Other times, there may be a rupture or injury to an artery delivering blood to a certain organ or tissue, starving those cells of the oxygen and nutrients that they need. Yet another possibility is that the blood vessels could become blocked with a blood clot. The clot may have formed at the site itself or it may have been carried to the spot from elsewhere in the body. The latter situation is referred to as thromboembolism.

What Is Pulmonary Embolism?

Pulmonary embolism is one of the best-known examples of thromboembolism. It occurs when a blood clot carried along by the blood becomes firmly lodged in an artery in the lung.

One of the primary causes for this is a condition known as deep vein thrombosis.

Pulmonary embolism typically results in symptoms such as breathlessness and lightheadedness because the heart, and thereby the rest of the body, is unable to receive the oxygen-rich blood it needs in order to continue functioning.

This condition can have severe long-term consequences and it can also be fatal if the patient is not attended to in time.

What Causes Pulmonary Embolism?

This condition generally arises as a complication of deep vein thrombosis. The latter involves the formation of a blood clot in one of the deep veins of the body, usually in the legs. This clot, or a piece of it, may come loose. It will then be carried along by the bloodstream, passing through the venous system until it finds its way into the pulmonary artery. It the clot is large enough, it can become lodged in the pulmonary artery or one of its branches, obstructing the flow of blood into the lungs.

Another way in which this can happen is when small clots progressively accumulate in the various branches of the pulmonary artery. The actual cause of the obstruction need not necessarily be a blood clot. It can also be an air bubble or a fat globule.

Risk factors for deep vein thrombosis are applicable for pulmonary embolism as well:

• Damage to the walls of the veins. This can happen when you have a habit of smoking.
• Prolonged bed rest or immobility.
• Having a family history of blood clots.
• History of deep vein thrombosis or pulmonary embolism.
• Trauma. This can include surgical trauma as well.
• Hormone replacement therapy.
• Having a blood clotting disorder.
• Dehydration.
• Heart disease.
• Lung disease.
• Vasculitis.
• Hepatitis.
• Inflammatory bowel disease.
• Cancer.
• Hughes syndrome.
• Obesity.
• Taking oral contraceptives.
• Being pregnant.
• Having varicose veins.
• Taking chemotherapy or radiation therapy.

What Symptoms Are To Be Expected?

Sometimes, the onset of symptoms is relatively gradual. It tends to begin with shortness of breath which can intensify progressively. Eventually, the patient also develops chest pain which can be quite severe. Sometimes, the condition is minor and temporary. The clot creating the obstruction may be small and it may resolve on its own. In instances of air or amniotic fluid embolism, the offending substances may get reabsorbed, resolving the obstruction.

When a person suffers from a pulmonary embolism, he or she may experience the following problems:

• Breathlessness.
• Chest pain.
• Breathing rapidly.
• Elevated heart rate.
• Weak pulse.
• Irregular heartbeat.
• Feeling faint or lightheaded.
• Dizziness.
• Bluish discoloration of the skin.
• Feeling restless or anxious.

What Are Some Likely Complications?

There can be a range of severe consequences when you have a pulmonary embolism. Receiving immediate medical help reduces the likelihood of developing complications. However, when the condition goes unrecognized or untreated, patients often do not survive.

The loss of blood supply to a certain section of lung tissue, unless promptly relieved, can cause permanent death of that section of tissue. This is known as infarction. When small clots accumulate progressively over an extended period of time, the patient will generally develop a condition known as pulmonary hypertension. This refers to elevated blood pressure within the lungs and even the right side of the heart. As a result, the patient could develop cardiac failure which may lead to death.

There is also the possibility of recurring embolism. Once the obstruction has been resolved, it can return unless the underlying problem has been rectified.

For instance, those who have suffered from one case of deep vein thrombosis are at a higher risk of experiencing a recurrence. And the more often that clots appear in the deep veins, the greater the likelihood of giving rise to pulmonary embolism.  

How Is Pulmonary Embolism Diagnosed?

It is not very easy to correctly identify the condition based only on its symptoms. Hence, the patient may need to undergo specialized imaging tests. These will help to precisely locate the obstruction. The following procedures may be involved:

• Physical examination.
• Medical history.
• D-Dimer test, a specialized blood test.
• Ultrasound.
• Echocardiogram.
• Pulmonary angiogram.
• Computerized tomography (CT).

What Is The Best Treatment? Is it preventable?

The first step involves making a correct diagnosis of the condition, identifying the nature and composition of the obstruction and the underlying cause for it. In case the blockage has been caused by blood clots, the immediate course of action would be to administer blood thinners to prevent more such clots from being formed. Some patients may require thrombolytic drugs in order to break down large clots.

Pulmonary embolism can develop swiftly and without prior warning. It is a medical emergency. However, the condition can also take on a chronic form and develop gradually as smaller clots pile up in the arteries of the lungs. The patient may notice progressive shortness of breath and chest pain. This can lead to high blood pressure in the lungs and heart which can cause more severe complications such as heart failure. Certain risk factors are modifiable and patients should take care to avoid these in order to prevent repeated occurrences.

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