Blood Clots, how they form and common causes

by admin | August 16, 2022 11:29 am

Blood clot is the body’s natural response to an injury or health condition that causes hemorrhage (bleeding). Since oxygen, which is the life-force of human beings, is transported through the blood, it is important to arrest blood loss at the earliest, which is what clotting achieves. However, when blood clots happen even when there is no injury or hemorrhage, it is not a good sign. Such blood clots travel through the circulatory system creating blocks in different parts of the body, leading to several complications.

When a blood clot is a good thing

Whenever there is an injury or hemorrhage due to a health condition, this is the sequence of events that unfold.

1. The blood comes in contact with the skin if the injury is external, or with the blood vessel walls if the bleeding is internal. This is a signal that a blood-vessel has ruptured and there is a danger of blood-loss.
2. In response to this signal, platelets found in the blood rush to the site of injury or bleeding. They stick to each other and the walls of the blood vessel thereby creating a ‘platelet plug’ at the site of leakage.
3. Proteins in the blood called as ‘clotting factors’ signal each other inciting a chain reaction. In response to this, certain proteins dissolved in the blood turn into long thin strands of filament called fibrin. The fibrin now looks like a net in which platelets get trapped.
4. To prevent this net from growing uncontrollably, some other proteins in the blood signal a stop to its growth.
5. Once the damaged tissue and the torn blood vessel start healing, the clot is no longer required. Then other proteins in the blood signal the fibrin strands to dissolve, after which the platelets and clot cells start moving. The clot cells are eventually broken down and flushed out of the body.

When Blood Clots are a bad thing

When blood clots are formed even when there is no injury or hemorrhage, it is not a good thing. It can be caused by several health conditions or even some medication. For example, some diseases can cause too many red-blood-cells and platelets in the blood, creating what is called a ‘hypercoagulable state’. Some conditions can prevent blood clots from breaking down when they are no longer needed. Some heart conditions or damage to blood vessels in the heart can affect blood flow and form unwanted clots.

Unwanted blood clots can get lodged in blood vessels at the same spot where they were created, thereby creating a permanent blockage there and disrupting blood-flow to one or more tissues served by that blood-vessel. This is called thrombosis. Or clots can move from the original spot where they were created, through the circulatory system, and get lodged in a blood vessel elsewhere, creating a blockage and disrupting blood-flow there. This is called embolism. When thrombosis happens in a vein, it’s called venous thrombosis, and if it happens in an artery, it’s called arterial thrombosis.

Symptoms of Blood Clots

Depending on the part of the body where the clot has developed, symptoms vary:

• Leg: The condition is called Deep Vein Thrombosis[2] and manifests as swelling, tenderness in the calf, redness, warmth and pain.
• Arm: The condition is called Deep Vein Thrombosis of the Upper Extremities and shows up as tenderness in the arm, warmth, swelling, cramping, redness or bluish tinge to skin there.
• Lung: Called Pulmonary Embolism, the condition is associated with shortness of breath (dyspnea), cough that brings up blood in the phlegm, chest pain that gets worse during breathing, racing heartbeat and incessant cough.
• Heart: This generally leads to heart attack and is associated with shortness of breath, chest pain, heaviness or squeezing sensation in the heart, numbness in the left arm, sweating, feeling light-headed, nausea and vomiting.
• Brain: Associated with stroke[3], manifests as weakness in the face or limbs, trouble speaking, dizziness, sudden or severe headache, loss of vision and mood swings.
• Abdomen: manifests as diarrhea, nausea, vomiting and severe abdomen pain[4].
• Atherosclerosis: Cholesterol deposits in the inner wall of arteries harden over time to form plaque. When plaque breaks off, tearing the wall of the artery, a clot is formed there.
• Cancer: Some cancers and cancer treatments[5] like chemotherapy or surgery cause tissue damage or inflammation in the body which triggers a blood clot to form there.
• Diabetes: Diabetes increases the risk of atherosclerosis (explained above).
• Genetic reasons: In some families, there may be an inherited blood-clotting disorder which increases the risk when combined with other factors. So also, family history of DVT.
• Heart failure: In this condition, the heart is not pumping blood the way it should. Blood flow becomes sluggish which eventually causes blood clots, which in turn trigger a heart attack.
• Immobility: Sitting for several hours at a stretch in the office, home, car or flight can cause blood to clot. So also being immobile while recovering from surgery.
• Arrhythmias: In this, the heartbeat becomes irregular. Blood starts pooling in places, causing blood clots.
• Pregnancy: The growing uterus can cause veins to compress, thereby reducing blood-flow to legs leading to deep-vein thrombosis. Also, as the woman nears delivery, ability of the blood to clot easily increases, to prevent excess bleeding during childbirth. This also increases the risk of unwanted blood clots.
• Obesity: Overweight people are at high risk of atherosclerosis.
• Sedentary lifestyle: People who do not exercise much or do not move much, are likely to develop clots easily. When combined with obesity, this can be deadly.
• Vasculitis: In this condition, blood vessels swell and sometimes develop tears. Clots begin to form at the tears or injured areas.
• Old age
• Smoking

Other Causes of Blood Clots

Venous thrombosis

• Any disease or trauma (injury) to veins in the leg. Ex sporting injuries, vehicle accidents or workplace accidents
• Fractures
• Certain medication
• Birth-control pills
• Hormone therapy
• Conditions such as heart disease, lung disease, Crohn’s disease
• A central venous catheter

Arterial thrombosis

• High blood pressure
• High cholesterol
• Genetic: a family history of arterial thrombosis

Other conditions associated with blood-clots

These conditions either cause or increase the risk of blood clots:

• Antiphospholipid syndrome: An autoimmune disorder that increases the risk of blood clots
• COVID-19 or Coronavirus disease
• Factor V Leiden: An abnormal mutation of clotting factors in the blood, which causes abnormal blood-clots in the lungs and legs.
• Polycythemia vera: A type of blood cancer that causes excess red blood cells to be produced, which eventually triggers blood clots.
• Peripheral Artery Disease (PAD): Narrowing of arteries in the body increases the risk of embolism.

Reviewed by Dr Suresh S Venkita, Group Medical Director, Kauvery Hospitals

Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai, Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.

Chennai – 044 4000 6000 • Trichy – Cantonment – 0431 4077777 • Trichy – Heartcity – 0431 4003500 • Trichy – Tennur – 0431 4022555 • Hosur – 04344 272727 • Salem – 0427 2677777 • Tirunelveli – 0462 4006000 • Bengaluru – 080 6801 6801

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