Mural Thrombus

A mural thrombus is a blood clot that forms and attaches to the inner wall of a blood vessel or heart chamber. When radiologists identify this finding on imaging studies, it can be a cause for concern, but understanding what it means can help patients and their families make sense of their medical reports.

What Is a Mural Thrombus?

A mural thrombus occurs when blood clots form along the walls of blood vessels or heart chambers. Unlike clots that completely block blood flow, mural thrombi partially adhere to vessel walls while allowing some blood to continue flowing past them. These clots typically develop in areas where blood flow is abnormal or where the inner lining of blood vessels has been damaged.

Blood normally flows smoothly through healthy vessels. However, when injuries, inflammation, or diseases affect vessel walls, platelets can stick to these damaged areas, initiating clot formation.

Common Locations for Mural Thrombi

Mural thrombi can appear in various locations throughout the cardiovascular system, though some areas are more commonly affected than others:

Heart Chambers

The heart is a frequent site for mural thrombus formation, particularly after a heart attack (myocardial infarction). When heart tissue dies during a heart attack, the inner surface of the heart wall becomes an ideal environment for blood clots to form.

The left ventricle, especially near the apex (the bottom tip of the heart), is a common location for post-heart attack thrombi. These clots appear as filling defects attached to the heart wall on imaging.

Aortic Thrombus

The aorta, the main artery carrying blood from the heart, can develop mural thrombi, particularly when abnormalities like aneurysms (bulges in the vessel wall) or atherosclerosis (plaque buildup) are present. These thrombi can be seen as irregularities protruding into the vessel lumen on CT or MRI scans.

Venous Thrombus

Large veins, especially in the legs (deep vein thrombosis) or the pelvic region, can develop mural thrombi. Unlike arterial thrombi, venous clots often occur in regions of slow blood flow.

How Mural Thrombi Appear on Imaging

Mural thrombi have distinctive appearances on various imaging modalities, making them recognizable to trained radiologists:

CT Imaging Findings

On computed tomography (CT) scans, mural thrombi typically appear as low-density filling defects attached to vessel walls. When contrast material is administered, the thrombus remains dark while flowing blood appears bright, creating a clear visual distinction.

CT angiography, which uses contrast specifically to highlight blood vessels, is particularly effective for identifying arterial mural thrombi. The three-dimensional reconstructions possible with CT angiography help clinicians visualize the size and extent of the thrombus.

MRI Characteristics

Magnetic resonance imaging (MRI) provides excellent soft tissue contrast, making it valuable for detecting and characterizing mural thrombi. Over time, as thrombi age, their MRI characteristics change.

Ultrasound Visualization

Ultrasound, particularly when enhanced with Doppler techniques, can identify mural thrombi as masses attached to vessel walls. The real-time nature of ultrasound allows for dynamic assessment of blood flow around the thrombus.

Echocardiography, a specialized form of ultrasound for the heart, is often used to detect cardiac mural thrombi, especially following heart attacks.

Clinical Significance and Complications

Understanding why mural thrombi matter requires knowledge of their potential complications:

Embolization Risk

Perhaps the most significant concern with mural thrombi is the risk of embolization. Fragments can break off from the main thrombus and travel through the bloodstream, potentially blocking smaller vessels downstream. These embolic events can cause:

  • Stroke (when emboli reach brain vessels)
  • Pulmonary embolism (when clots travel to the lungs)
  • Peripheral arterial occlusion (when emboli block arteries in the limbs)

Organ Dysfunction

Depending on their location, mural thrombi can directly affect organ function. Cardiac thrombi may interfere with normal heart contractions, while arterial thrombi can reduce blood flow to vital organs, leading to ischemia or infarction if blood flow becomes critically restricted.

Treatment Approaches

When radiologists detect mural thrombi on imaging studies, several treatment options may be considered:

Anticoagulation Therapy

Blood thinners, such as heparin or warfarin, are often prescribed to prevent thrombus growth and reduce the risk of embolization. These medications don’t dissolve existing clots but help prevent new ones from forming while the body’s natural mechanisms work to break down the thrombus.

Thrombolytic Therapy

In certain urgent situations, clot-dissolving medications (thrombolytics) may be administered to actively break down the thrombus. This approach carries higher bleeding risks.

Surgical Intervention

Some cases require surgical removal of the thrombus, particularly when clots are very large or when anticoagulation is contraindicated. Endovascular techniques now allow for minimally invasive removal of some thrombi.

Follow-Up Imaging

Once a mural thrombus is identified, follow-up imaging is typically recommended to monitor for:

  • Changes in thrombus size
  • Signs of embolization
  • Response to treatment
  • Development of new thrombi

Conclusion

Mural thrombi are blood clots attached to vessel or heart chamber walls.  They carry risks of embolization and can cause complications. Through various imaging techniques including CT, MRI, and ultrasound, radiologists can accurately identify these clots and guide appropriate treatment. Knowledge about mural thrombi helps patients better understand their conditions and participate more actively in treatment decisions.

References

  1. https://www.jvascsurg.org/article/S0741-5214(99)70047-9/fulltext
  2. https://angiologist.com/mural-thrombus/
  3. https://www.sciencedirect.com/science/article/pii/S0741521414016231
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