Introduction

A medical condition where a blood clot (thrombus) develops inside a blood vessel is called ‘Thrombosis’. Thrombosis can happen in an artery or a vein. It is important to diagnose the presence of a thrombosis because it can potentially block the blood vessel and lead to life-threatening conditions such as a heart attack (myocardial infarction), stroke or pulmonary embolism (PE), depending on the location of the blood clot or ‘thrombus’.¹ Globally, thrombosis is a major mortality contributor. Understanding and creating awareness about the types of thrombosis, its symptoms, the complications it can lead to, and the treatment is important to address this commonly seen medical condition.¹

What is thrombosis?

Let us take a simple example to understand what a thrombosis is. Imagine a car that needs fuel to function. The fuel goes through a fuel pipe to the engine, where it mixes with the air and ignites sparks that create power. If there is any air or debris that is in the fuel, it will obstruct the flow of fuel to the engine, and the car will not work properly. Just like the car, our human body is made up of vital organs, blood vessels and the blood that flows inside these vessels or pipes. Blood is always flowing through our body, either from arteries that carry oxygen-rich blood to different parts of the body or through the veins that carry oxygen-poor blood from different parts of the body to the heart. In the case of the human body, the debris is in the form of clots in the blood, which, when they become larger, can completely obstruct the flow of blood, leading to what is called thrombosis. Now imagine these clots get stuck in the blood vessels that supply the vital organs, such as the heart, brain, lungs, etc. When that happens, it leads to life-threatening conditions that we all have heard of. Thrombosis is a complex process and is caused by hypercoagulability, damage to the endothelial lining or by stasis.¹ The typical symptoms of thrombosis are:

• Pain
• Swelling
• Redness in the affected area 

Types of thrombosis

Arterial thrombosis

Now that we know that thrombosis is the formation of a blood clot in a blood vessel, let us understand the types of thrombosis.

When the clot formation or thrombus occurs in an artery, it is called ‘arterial thrombosis’. Arterial thrombosis is caused by to change in the blood flow, an injury to the artery leading to clot formation or due to atherosclerotic plaque build-up in the lumen of the arteries. As arteries supply oxygen-rich blood to the organs, a blockage in the supply of oxygen-rich blood affects their functionality and leads to serious consequences. 

Common locations include:

• Heart (leading to a heart attack)
• Brain (leading to stroke)
• Limbs (leading to peripheral artery disease)

Symptoms:

• Sudden severe pain
• Tingling or numbness
• Cold skin

Complications:

• Heart attack
• Stroke
• Ischemia

Risk Factors:

• High blood pressure (hypertension)
• Smoking
• High cholesterol
• Uncontrolled diabetes
• Obesity
• Sedentary lifestyle
• Genetic predisposition

Venous thrombosis

Clot formation occurring in a vein is called ‘Venous thrombosis’.

It is often due to slow blood flow or stagnant blood in the blood vessel (stasis), injury to the vein, or a higher tendency to form clots (hypercoagulability), together known as Virchow's Triad.^2,3,4 The umbrella term used is Venous Thromboembolism (VTE).

Common locations include:

• Deep veins (of the legs)
• Lungs- Pulmonary Embolism (PE)

Symptoms:

• Swelling
• Redness
• Warm affected areas
• Pain
• Shortness of breath, if the lungs are involved
  

Complications:

• Pulmonary embolism (PE)
• Chronic venous insufficiency

Risk Factors:

• Prolonged immobility
• Surgery
• Pregnancy
• Obesity
• Genetic clotting disorders

Key differences between arterial and venous thrombosis²

Diagnosis of thrombosis

• Arterial Thrombosis: Angiography, CT scan, MRI, ultrasound
• Venous Thrombosis: Ultrasound, D-dimer blood test, CT pulmonary angiography (for PE)

Treatment of thrombosis⁶

Arterial thrombosis

Treatment of arterial thrombosis typically focuses on breaking up the blood clot and preventing further clot formation. This may involve:

1. Medications: Antiplatelet therapy (e.g., aspirin, clopidogrel)
2. Procedures: Angioplasty, stenting, or surgery
3. Lifestyle changes: Diet, exercise, smoking cessation

Venous thrombosis

The treatment for venous thrombosis aims to prevent the clot from getting bigger, reduce the risk of complications, and prevent new clots from forming. Common treatments include:

1. Medications: Anticoagulants (e.g., warfarin, heparin, direct oral anticoagulants)
2. Compression therapy: For DVT
3. Thrombolytic therapy: Medications that dissolve the clot may be used to break the clots as well
4. Surgery: In severe cases (e.g., PE), surgery may be needed to remove a clot or place a filter in the vein to prevent clots from travelling to the lungs

Prevention of thrombosis

Thrombosis can be prevented to a large extent by making some simple and healthy lifestyle changes, such as:

• Having a balanced diet
• Having a moderate daily exercise or physical activity
• Smoking cessation
• Regular monitoring in high-risk individuals (e.g., those with genetic predisposition or undergoing surgery)
• Use of blood thinners for patients at risk as a preventive measure

Summary

‘Thrombosis’ is the formation of a blood clot in a blood vessel that can occur in an artery or a vein. When a clot forms in an artery, it is called ‘arterial thrombosis’ and when it forms in a vein, it is called ‘venous thrombosis’. Understanding the difference between an arterial and a venous thrombosis helps one recognise the symptoms and seek prompt treatment. Arterial thrombosis has an acute, severe onset that can lead to life-threatening conditions such as heart attacks and strokes, whereas venous thrombosis can lead to Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE). Early detection, medication, and lifestyle modifications can help control this condition. It is important to seek medical attention if you experience any of the symptoms that can be a result of thrombosis.