What Causes Blood Clots in Lungs

Blood clots in the lungs, or pulmonary embolism (PE), happen when blood clots block blood flow to your lungs. This serious condition puts your life at risk and needs quick medical treatment. The clots usually form in other parts of your body, break loose, and travel through your blood until they get stuck in the small blood vessels of your lungs.

When this happens, these clots stop oxygen-rich blood from flowing properly, which can damage your lungs and strain your heart. The blockage can affect one or more areas of your lungs, making breathing hard and causing chest pain.

Understanding what causes these blood clots is crucial because it helps you recognize your risk factors and take steps to prevent them. Early detection and treatment of blood clots can save your life, so knowing the warning signs and getting medical help quickly matters.

What Are Blood Clots?

Blood clots are aggregates of blood that transition from liquid to gel-like consistency. They serve as your body’s natural band-aids when you get hurt. When you cut yourself or get an injury, your blood forms these clots to stop the bleeding. This natural clotting process promotes healing and prevents you from losing excessive blood. Think of it like a plug that seals a leak in a pipe.

However, blood clots can develop unexpectedly. Normal clots form on the outside of blood vessels when you’re injured. Even without damage, abnormal clots grow inside your blood vessels. These undesirable clots might create major complications because they obstruct blood flow throughout your body.

Types of Blood Clots

Venous clots form in the veins that carry blood to the heart. The most lethal kind is deep vein thrombosis (DVT), which frequently develops in the deep veins of the legs. DVT is hazardous because clots might detach and go to the lungs.

Arterial clots form in the arteries that carry blood out of the heart. While they happen less often than venous clots, they can cause serious problems. They can quickly cut off blood flow to essential organs like the heart, brain, or lungs.

How Do Blood Clots Cause Pulmonary Embolism?

Blood clots that cause pulmonary embolism usually start in the deep veins of your legs. These clots begin when blood moves too slowly or pools in your veins, often because you haven’t moved for a long time. Think of it like a slow-moving stream where leaves and twigs collect in one spot.

Once these clots form, they can break loose from the vein wall. When this happens, the blood flow carries them through more prominent veins, up to your heart, and into your lungs. The blood vessels in your lungs get smaller like tree branches getting thinner at the tips. The clot finally becomes lodged, making the ship too small to get through.

Impact on the Lungs

When a clot blocks a blood vessel in your lungs, it creates serious problems. The blocked vessel can’t deliver oxygen-rich blood to that part of your lung. This means:

The obstructed lung tissue cannot receive the oxygen required to function correctly.
Your blood cannot deliver new oxygen throughout your body.
Your heart has to function harder to push blood across the barrier.
If the clot is large or if you have many clots, parts of your lung tissue might die
Other organs in your body may not receive enough oxygen, which might cause them to stop performing correctly.

The larger the clot or the number of clots, the more hazardous the scenario. This is why getting quick medical help for a pulmonary embolism is essential.

Main Causes of Blood Clots in Lungs

Deep Vein Thrombosis (DVT)

Deep vein thrombosis occurs when blood clots develop within your body’s massive, deep veins. These clots are the most common reason people get blood clots in their lungs. DVT usually starts in your legs, often in the calf or thigh, where blood can move slowly if you don’t move around much. Think of it like a garden hose where water moves so slowly that dirt collects and forms clumps.

Although leg clots are the most common, DVT can affect other parts of the body. Clots might develop in your arm veins, especially if you have a medical device like an IV line or a pacemaker wire. Sometimes, clots form in the veins of your pelvis, which often happens after hip surgery or during pregnancy.

Other Rare Causes

Several unusual things can block blood vessels in your lungs:

When you break a bone, tiny bits of fat can leak from the bone marrow into your blood. These fat droplets can travel to your lungs and block blood vessels.
During childbirth, the fluid that surrounds the baby (amniotic fluid) can sometimes enter the mother’s bloodstream and cause blockages.
Air bubbles might enter your blood vessels during medical procedures or after serious injuries. These bubbles can travel to your lungs and block blood flow.
In some cancer cases, clumps of cancer cells break away from tumors and get stuck in lung blood vessels.

These rare causes are different from normal blood clots because the blockage isn’t made of clotted blood. However, they can be just as dangerous and need prompt medical attention.

Risk Factors of Blood Clots in Lungs

Virchow's Triad: The Three Main Contributors

1. Sluggish Blood Flow

When your blood moves too slowly, it’s more likely to form clots. Think of a slow-moving stream where leaves collect in quiet pools. Your blood can slow down for several reasons:

Long periods of not moving, such as:
Being stuck in bed after surgery or illness
Sitting for many hours on long flights or car trips
Working at a desk all day without getting up
Having paralyzed muscles that don’t help push blood back to your heart
Living a lifestyle where you rarely move or exercise

2. Hypercoagulability (Increased Clotting Tendency)

Some people’s blood clots more quickly than usual. This can happen because of:

Genes you inherit from your parents that make your blood clot too easily

Taking certain medicines:

Birth control pills
Replacement therapy for hormones
Some Cancer Therapies

Medical conditions:

Cancer increases the likelihood that your blood may clot.
Pregnancy increases clotting factors in your blood
COVID-19 infection can make your blood stickier
Being very overweight
Heart failure
Recent major surgery

3. Blood Vessel Wall Damage

Just like a rough spot in a pipe can catch debris, damage to your blood vessels can start clots. This damage might come from:

Physical injury to your veins
Having surgery
Getting an IV or catheter put in
Inflammation from:
Infections
venous diseases that affect your blood vessels
Autoimmune conditions

B. Lifestyle and Medical Factors

Your everyday behaviors and health circumstances may raise your risk of blood clots.

Smoking

Increases the risk of blood clots.
Damages blood vessel walls
Thickens your blood
Reduces oxygen in your blood

Obesity

It increases pressure on your veins.
It reduces blood flow.
Often comes with less physical activity
It can cause inflammation in your body

Advanced Age

Blood vessels become less flexible
People move around less
More likely to have other health problems
There is a higher chance of needing surgery

Each of these risk factors increases your probability of developing blood clots. Having more than one risk factor makes clots even more likely. The good news is that you can manage some of these dangers by:

Moving constantly
Maintaining an appropriate weight.
Not smoking.
Following your doctor’s advice about medications and treatment

Related: Symptoms of Blood Clot in Arm

Uncommon Causes of Deep Vein Thrombosis (DVT) and Pulmonary Embolism

1. Advanced Age and Reduced Mobility

As people get older, their risk of blood clots increases for several reasons:

Vessels of blood become less flexible and more susceptible to injury.
Older adults often move less during the day
Many take medications that might increase clotting risk
They’re more likely to have surgeries or illnesses that require bed rest

Reduced mobility in older adults happens because:

Joints become stiff and painful
Muscles get weaker
Balance problems make them afraid of falling
Chronic health conditions limit activity

2. Non-Blood Clot Emboli

These unusual blockages differ from regular blood clots but can be just as profound:

Fat Embolism

This happens when fat particles from bone marrow enter the blood
Most common after breaking large bones like the thigh bone
Usually shows up 1-3 days after injury
It can cause breathing problems, confusion, and rash

Air Embolism

Air bubbles enter blood vessels during:
Medical procedures involving central lines
Chest injuries
Scuba diving accidents
Can block blood flow suddenly
Requires immediate medical treatment

Amniotic Fluid Embolism

Infrequent but dangerous pregnancy complication
This occurs when the fluid from the embryo enters the mother’s circulation.
Usually happens during delivery or right after
Causes severe breathing problems and heart issues

3. Tumor Emboli

Cancer-related clots are different from regular blood clots:

Tumor pieces split off and move to the lungs.
Most common in breast, lung, and stomach cancers
More challenging to treat than regular blood clots
May need both blood thinners and cancer treatment

These uncommon causes need different treatments than regular blood clots. Doctors must:

Find the exact cause
Treat both the lung blockage and the underlying problem
Monitor closely for complications
Often use specialized treatments beyond blood thinners

Early recognition and proper medical care are essential for all these conditions. Each needs its specific treatment approach for the best possible outcome.

Preventing Blood Clots in Lungs

1. Lifestyle Modifications

You may take various steps to reduce your risk of blood clots in your lungs. One of the most important things you may do for your well-being is to exercise regularly. If you’re on a lengthy flight or driving journey, get up and walk every few hours. Try simple exercises like ankle circles or leg stretches from your seat when you can’t get up. If you are in the hospital, your physicians may advise you to start moving as soon as it is safe. Even small movements help keep your blood flowing well.

Maintaining a healthy weight through proper diet and exercise helps prevent clots because extra weight puts pressure on your veins. If you smoke, quitting is crucial because smoking damages your blood vessels and makes your blood more likely to clot. Regular exercise helps with weight and keeps blood flowing smoothly through your vessels.

2. Medical Interventions for High-Risk Individuals

If you are more likely to develop blood clots, your doctor may offer preventative medications. Blood thinners, often known as anticoagulants, prevent the development of blood clots. These medicines come as pills you take by mouth or shots you give yourself under your skin. Your doctor will help you choose the optimal kind for your needs and track their efficacy.

Compression stockings are unique tight socks that gently squeeze your legs. This pressing helps to redirect blood back to your heart instead of collecting in your legs. They perform best when ordered in the right size and worn correctly. Your doctor may suggest compression stockings and show you how to use them properly. Your doctor can prescribe compression stockings and demonstrate how to wear them correctly.

Worried About Blood Clots? Let's Create Your Prevention Plan Together

Blood clots in the lungs are serious but often preventable. They usually start as clots in your legs that break loose and travel to your lungs, though sometimes they can come from other sources like broken bones, air bubbles, or cancer cells. Knowing what causes these clots allows you to identify your risk factors and take precautions to avoid them.

If you have risk factors like being older, overweight, or recovering from surgery, talk to your doctor about prevention strategies. At our primary care clinic, our experienced primary care physicians help you understand your personal risk factors and develop a tailored prevention plan.

Don’t wait until symptoms appear, get in touch and we will help you prevent complications before they start.

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FAQs

What is the most common cause of blood clots in the lungs?

Deep vein thrombosis (DVT) in the legs is the leading cause. These clots develop in deep leg veins when blood flows slowly and frequently due to extended immobility and can break free, moving via the circulation to the lungs.

What are the first signs of a blood clot in your lung?

The early symptoms are shortness of breath, severe chest discomfort that increases with deep breathing, a fast pulse, an inexplicable cough (often with bloody mucus), and lightheadedness. Some people report leg edema or soreness.

Can a person recover from blood clots in the lungs?

Yes, most people can recover from pulmonary embolism with proper medical treatment. Recovery typically involves blood-thinning medications, close medical monitoring, and lifestyle changes. Full recovery can take several months.

What is life expectancy with blood clots in the lungs?

When caught early, the survival rate for treated pulmonary embolism is about 95%. Most patients who receive prompt treatment can live an expected lifespan. However, without treatment, severe cases can be life-threatening within hours.

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