What Blood Clot in The Lungs Do During a Pulmonary Embolism

You may know that a blood clot in the lung is dangerous. But what does a blood clot in the lung do to breathing over time? What is actually happening inside your lungs, minute by minute, when that clot blocks blood flow?

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Blood Clot in the Lung: How It Affects Breathing Over Time

Pulmonary embolism (PE) kills hundreds of thousands annually. Yet most patients cannot explain what a lung clot actually does to the body, which is why the symptoms are so often dismissed until it is too late. Check out our complete guide to pulmonary embolism and DVT.

The Direct Answer.. What a Blood Clot in the lungs does the Moment It Arrives

A blood clot blocks one or more pulmonary arteries, the vessels carrying blood from the heart to the lungs for oxygenation.
Oxygen cannot enter the bloodstream properly. Blood oxygen levels (SpO2) begin to drop.
The right side of the heart is forced to pump against abnormally high resistance, causing right heart strain.
Within minutes to hours: breathing becomes labored, heart rate rises, and blood pressure may fall in severe cases.

Step by Step.. What Happens Inside the Lungs

This mismatch quickly escalates to more serious problems. The blockage creates pressure gradients across the pulmonary circulation that worsen over time if untreated.

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Step 1 : The Clot Arrives and Blocks the Artery

Most PE clots originate in the deep leg veins (DVT) and travel through the venous system to the lungs.

A clot can block a large central pulmonary artery (massive PE) or smaller branches (submassive or small PE).

The size and location of the blockage determine everything that happens next. Peripheral clots affect smaller lung segments, while central clots compromise larger lung volumes immediately.

Step 2: Dead Air Space Forms (V/Q Mismatch)

The blocked area of the lung still receives air through normal breathing, but no blood arrives to exchange oxygen with.

This is called ventilation-perfusion (V/Q) mismatch: air goes in, but no gas exchange occurs.

The affected lung tissue shuts down functionally, contributing nothing to oxygenation. Healthy lung areas compensate by constricting blood flow, but this increases overall pulmonary pressure.

Step 3: Pulmonary Infarction (in Some Cases)

If the blocked artery supplies a lung segment with no backup blood supply, that segment begins to die.

It occurs in approximately 10-15% of PE cases.

Results in pleuritic chest pain (sharp, worsens with each breath) and sometimes coughing up blood (haemoptysis). Infarction areas show characteristic wedge-shaped opacities on imaging.

Step 4: The Right Heart Comes Under Extreme Pressure

The right ventricle must push blood through increasingly blocked pulmonary arteries.

It dilates and weakens under this strain, a condition called acute cor pulmonale.

Even submassive PE often shows echocardiographic right ventricular strain.

Small vs. Massive PE: Why the Same Disease Has Vastly Different Outcomes

Small subsegmental PE: may cause mild breathlessness or be nearly asymptomatic.. sometimes discovered incidentally.
Submassive PE: significant right heart strain but blood pressure is still maintained-serious without treatment.
Massive PE: blood pressure collapses, oxygen crashes, cardiac arrest risk is high-requires immediate emergency intervention.

At Dr. Saher Clinics, we prioritize swift recovery. Patients with smaller, uncomplicated clots often see resolution within two weeks. For most larger, complex cases, our specialized, single-session catheter intervention successfully restores blood flow and avoids the need for open surgery.

Criteria	Small Clot	Large Clot	At Dr. Saher Clinics
Size	1-2 cm	>5 cm	High diagnostic accuracy
Symptoms	Mild pain	Severe breathlessness	Treatment within 14 days
Treatment	Medication + exercise	IV + oxygen	High success rate
Hospital Stay	1-2 days	5-7 days	Same-day discharge option

Type	Symptoms	Outcomes	Treatment
Small subsegmental PE	Mild breathlessness or asymptomatic	Sometimes discovered incidentally	Anticoagulation
Submassive PE	Significant right heart strain	Blood pressure maintained, serious without treatment	Advanced therapies if needed
Massive PE	Blood pressure collapse, oxygen crash	High cardiac arrest risk	Immediate emergency intervention

Why Fast Treatment Changes Everything

The Catheter Option – Restoring Blood Flow Without Open Surgery

A catheter is guided through a large vein directly into the blocked pulmonary artery.

The clot is mechanically broken up or aspirated (suctioned out). This is a mechanical thrombectomy.

Dr. Saher Arour received a medical innovation award in Dubai for his catheter-based treatment for PE. Learn more about Catheter-Based Pulmonary Embolism Treatment.

What Happens to the Lung After Successful Treatment

Blood flow is restored. Oxygen levels typically improve during or immediately after the procedure.

Right heart pressure normalizes over hours to days as the blockage clears.

Most patients feel significantly better within 24-48 hours of successful treatment. Residual clots continue dissolving naturally over weeks with anticoagulation support.

Symptoms That Demand Immediate Action

These symptoms signal that something serious is happening in your lungs:

Sudden shortness of breath with no other explanation.
Sharp chest pain that worsens when breathing deeply.
Rapid heart rate combined with breathlessness or dizziness.
Coughing up blood (haemoptysis), a sign of pulmonary infarction.
Fainting or near-fainting, a warning sign of massive PE and collapsing blood pressure.
Call emergency services immediately. Do not drive yourself to the hospital.

Frequently Asked Questions

Can the lung heal fully after a pulmonary embolism?

In most cases, yes. With proper anticoagulation, the clot dissolves over weeks to months and lung function returns. Areas of pulmonary infarction take longer and may leave a small scar, but significant permanent damage is uncommon with timely treatment.

Does a pulmonary embolism always cause chest pain?

No. Some PE cases present with no chest pain. The most consistent symptom is unexplained breathlessness. This is why PE is frequently missed in its early stages.

How does a DVT clot reach the lung?

The clot detaches from a deep leg vein, travels through the venous system into the right side of the heart, and is then pumped into the pulmonary arteries, where it becomes a pulmonary embolism.

Is pulmonary embolism always life-threatening?

Not always. Small PE can resolve with anticoagulant medication alone. However, it is always serious: even small clots can grow or trigger larger events. Massive PE carries a mortality rate of up to 30% without prompt treatment.

How is a pulmonary embolism diagnosed?

The gold standard is a CT pulmonary angiogram (CTPA), which shows the clot’s exact location and size. A D-dimer blood test is used as a screening tool when PE is suspected but not yet confirmed.