Anticoagulant Therapy For Pulmonary Embolism

Overview of pulmonary embolism (PE)

Pulmonary Embolism (PE) is when there is a blood clot in the lung, this happens when the blood clot travels from your leg to the lungs and stays there. This can cause an issue with the blood flow and the oxygen levels in your lungs, increasing the blood pressure in the arteries.¹

In most cases, the treatment consists of anticoagulant medications, also known as blood thinners. These are used because they can prevent your blood from clotting and therefore prevent future blood clots.^1,2 

Cause of pulmonary embolism

Formation of blood clots

Blood clots normally happen, when there is damage in the blood vessels. This can happen because of various reasons, such as injuries or being immobile for long periods of time. Platelets present in the blood will then begin to join the cut edges of the vessels by releasing chemicals. A semi-solid mass is produced from the clotting factors, which are sticky substances that make the blood clump together. Once these are formed they can travel from the leg to other parts of the body, such as the brain, lungs or the heart.³

Risk factors of pulmonary embolism

Some of the common risk factors for PE include:^1,2

• Having a blood clot in the leg
• Birth control medication
• Frequent smoking
• History of heart failure
• Having a Body Mass Index (BMI) greater than 30 
• Recent injury to veins
• Being inactive for long period of time

Diagnosis of pulmonary embolism

Diagnosis of PE is usually made using the following symptoms:

• Sudden shortness of breath 
• Unexplained sharp pain in your chest, nack, jaw, shoulder and arm 
• Cough with or without bloody mucus
• Rapid heartbeat
• Pale, bluish pulse
• Excessive sweating
• Wheezing
• Feeling lightheaded or Fainting

The diagnostic tools and imaging techniques used to make the diagnosis are:^1,2

• Blood tests
• CT angiogram
• Ultrasound of the leg
• Ventilation/perfusion scan - scan that can detect clots in your lung

Types of Anticoagulant Therapy

There are various types of anticoagulants that doctors may give.⁴

Heparin

Heparin is a medication that prevents clotting by activating the body’s anti-clotting programs that use a special type of protein called antithrombin. Heparin works by activating the special protein which then keeps other parts of the clotting programs from working properly. 

Low molecular weight heparin (LMWH)

This is a type of heparin, and as the name suggests is a low molecular weight, meaning it has shorter molecules, so it can only attach to antithrombin. This also means that it has longer-lasting effects, is more predictable and does not need very close monitoring. 

Warfarin (vitamin K antagonist)

This is a vitamin K antagonist, meaning it blocks the use of vitamin K, which is an essential vitamin in the clotting process. But, with this type of anticoagulant, you have to be careful with the dosing and it requires very close monitoring and regular lab testing to prevent complications. When dosing is not precise, it can lead to severe bleeding. 

Direct oral anticoagulants (DOACs)

These are medications that can be taken regularly and are used when warfarin is not an option to take. Some examples include Rivaroxaban, Apixaban, Dabigatran and Edoxaban.  

Monitoring and Management

Most anticoagulants will require regular monitoring by your local GP. These are done using common tests that can test for bivalirudin and argatroban in the blood, including aPTT and the ACT tests; and in some cases, thrombin time test is also done. After the results, adjustments to the dose of the medication and the duration of the medication can be made.⁵

Duration of anticoagulant therapy

The optimal duration of anticoagulation is not known, it will depend on how severe your case is, but if you have an acute form of PE, then the anticoagulants should not be taken for more than 3 months.^5,6

• Acute treatment phase - focuses on the safe initiation of the full dose of anticoagulation, usually administered by intravenous methods. 
• Long-term prophylaxis and prevention of recurrent PE -  it is advised for you to take frequent routine check-ups, that your drug-drug interactions are studied, and your renal functions are checked.

Special considerations

Anticoagulation in pregnancy

In pregnancy, if you are diagnosed with PE, then the main treatment that would be given to you would be LMWH for a minimum of 3 months and at least 6 weeks post-pregnancy. LMWH are safe for pregnancy use, effective and have low associated bleeding risk.⁴

Complications and adverse events

The possible complications and adverse events that are accompanied with the use of anticoagulants is as follows:

• Bleeding complications - can have more bleeding depending on the anticoagulant use
• Blue or purple toes
• Skin necrosis - rare
• Heparin-induced thrombocytopenia
• Indigestion
• Bleeding in the gastrointestinal tract

Future Directions and Emerging Therapies 

Due to the complications with the use of anticoagulants, mainly bleeding events, researchers are looking for ways to help prevent this and improve the patients' quality of life. In recent years, studies have shown the use of factor XIa inhibitors to be promising in preventing blood clots without having increased chances of bleeding, which is shown in more traditional anticoagulants. This new approach has also shown the potential to improve the safety and the quality of life of patients in anticoagulation therapy.⁷ 

Summary

PE is a serious condition that can be life-changing, but treatments are helping many people with PE, so it is important to get a quick diagnosis and treatment. Be on the lookout for symptoms if you have a higher risk for PE and do what you need to do to help prevent it by getting help.