Cardiac Thrombus on CT
Understand Cardiac Thrombus on CT in Heart Cardiac CT imaging, what it means, and next steps.
30-Second Overview
Intracardiac filling defect, typically in left atrial appendage (LAA) or ventricle; low attenuation (30-50 HU), does not enhance with contrast
Cardiac thrombus carries high embolic risk. LAA thrombus: 15-20% stroke risk without anticoagulation. Detection critical for anticoagulation decisions.
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Imaging Appearance
Cardiac CT FindingIntracardiac filling defect, typically in left atrial appendage (LAA) or ventricle; low attenuation (30-50 HU), does not enhance with contrast
Clinical Significance
Cardiac thrombus carries high embolic risk. LAA thrombus: 15-20% stroke risk without anticoagulation. Detection critical for anticoagulation decisions.
Understanding Cardiac Thrombus
A cardiac thrombus is a blood clot that forms inside the heart, most commonly in the left atrial appendage (LAA) in patients with atrial fibrillation or in the left ventricle after a heart attack. These clots can break free and travel to the brain, causing stroke.
Intracardiac filling defect with low attenuation (30-50 HU) that does not enhance with contrast
Here's how accurate CT is at detecting cardiac thrombus:
High sensitivity for thrombus detection
Correctly rules out healthy patients
Annual new cases
Think of a cardiac thrombus like a clot forming in a slow-moving stream—when blood doesn't flow smoothly through the heart (due to irregular rhythm or weakened muscle), clots can form. If these break loose, they can travel to the brain and cause stroke.
What Is Cardiac Thrombus?
Cardiac thrombi are blood clots that form within the heart chambers. They develop when blood flow becomes stagnant or when the heart lining is damaged after injury.
Common locations:
- Left atrial appendage (LAA) - most common, associated with atrial fibrillation
- Left ventricle (LV) - post-myocardial infarction, apical thrombus
- Right atrium/ventricle - less common, usually from indwelling catheters or devices
Types of thrombus:
- Mural thrombus - attached to heart wall, can be sessile or pedunculated
- Pendulating/mobile thrombus - higher embolic risk
- Organized thrombus - older, may be calcified
Why detection matters:
- LAA thrombus carries 15-20% annual stroke risk without anticoagulation
- Detection guides anticoagulation decisions
- Critical before cardioversion (electric shock to heart)
- Influences stroke prevention strategy
How Cardiac Thrombus Appears on CT
Cardiac CT with ECG gating can detect intracardiac thrombus, although transesophageal echocardiography (TEE) remains the reference standard for LAA thrombus detection.
What Normal Heart Chambers Look Like
Cardiac chambers appear uniformly filled with contrast-enhanced blood. No filling defects. Left atrial appendage fills completely with contrast. Chamber walls smooth and normal thickness. No abnormal masses or thrombi. Normal myocardial enhancement.
What Cardiac Thrombus Looks Like
Filling defect within cardiac chamber (most commonly LAA). Thrombus appears lower attenuation (30-50 HU) than adjacent blood. Does not enhance with contrast. May be rounded, oval, or irregular. LAA thrombus: complete non-filling of appendage. LV thrombus: apical filling defect, often with dyskinetic segment.
Key Findings Pattern
When evaluating for cardiac thrombus on CT, radiologists assess:
Key Imaging Findings
Thrombus location
Left atrial appendage (most common), left ventricle apex, right heart chambers
Attenuation value
Thrombus typically measures 30-50 HU on contrast-enhanced scan
Lack of enhancement
Thrombus does not enhance with contrast administration
Morphology and mobility
Shape (round, oval, irregular) and attachment to wall
Associated findings
Atrial fibrillation signs (enlarged LA), LV aneurysm/dyskinesis, wall motion abnormality
Differential from normal structures
Pectinate muscles (LAA trabeculations), prominent cristae terminalis
When Your Doctor Orders This Test
Here's a typical scenario where CT is performed to evaluate for cardiac thrombus:
Clinical Scenario
Common indications:
- Atrial fibrillation before cardioversion
- Stroke workup to identify cardiac source
- Post-MI LV thrombus surveillance
- Evaluation of cardiac mass
Why TEE is often preferred:
- Higher sensitivity and specificity for LAA thrombus
- Better visualization of LAA anatomy
- No radiation exposure
- Can assess thrombus mobility in real-time
Differential Diagnosis
Several conditions can mimic cardiac thrombus on imaging:
What Else Could It Be?
Filling defect with low attenuation (30-50 HU), no enhancement, typical location (LAA in AF, LV apex post-MI). Confirmed with TEE. Treatment: anticoagulation (warfarin, DOACs). Duration depends on clinical context.
Normal LAA trabeculations appearing as fine linear structures. Not mass-like. Recognized by experienced readers. TEE confirms normal anatomy. No treatment needed.
Poor contrast opacification of chamber mimics thrombus. Contrast swirl or mixing artifact may be visible. Repeat scan with better contrast opacification or TEE clarifies. No thrombus present.
Typically in left atrium arising from interatrial septum (myxoma). May show some enhancement (unlike thrombus). Usually pedunculated. Surgical removal required. TEE and MRI help characterize.
Motion blur from cardiac motion or breathing. Beam hardening from adjacent calcifications. Recognized by characteristic appearance. Confirmed on repeat imaging or alternative modality.
How Accurate Is CT for Cardiac Thrombus?
Cardiac CT has good but not perfect accuracy for thrombus detection:
Cardiac CT detects most LAA thrombi, but small thrombi or those adjacent to pectinate muscles may be missed. TEE remains the reference standard with sensitivity ＞95%. CT is useful when TEE is not available or contraindicated.
Patients with atrial fibrillation who are not anticoagulated have significant risk of LAA thrombus formation. This risk justifies thrombus exclusion before cardioversion. Anticoagulation reduces both thrombus formation and stroke risk.
Left ventricular thrombus commonly forms after anterior myocardial infarction, especially with apical akinesis or aneurysm. Systemic anticoagulation reduces thrombus formation and embolic complications. Serial imaging may be used for surveillance.
What Happens Next?
Management depends on thrombus location, mobility, and underlying cause:
What Happens Next?
Thrombus confirmation and characterization
CT finding confirmed with TEE (gold standard). Assess thrombus size, mobility, and attachment. LAA thrombus: anticoagulation before any cardioversion. LV thrombus: anticoagulation typically for 3-6 months.
Anticoagulation therapy
LAA thrombus: warfarin (INR 2-3) or DOAC for at least 3 weeks before cardioversion. Continue anticoagulation for at least 4 weeks after successful cardioversion (longer if AF recurs). LV thrombus: anticoagulate for 3-6 months.
Underlying condition management
Atrial fibrillation: rhythm or rate control, stroke prevention. LV dysfunction: guideline-directed medical therapy. Heart failure management. Address any structural heart disease. Consider LA appendage closure device.
Reassessment imaging
Repeat imaging (TEE or CT) after anticoagulation to confirm thrombus resolution. LAA thrombus: reassess before cardioversion if initially present. LV thrombus: follow imaging to document resolution. Persistent thrombus may require extended anticoagulation.
Long-term stroke prevention
Atrial fibrillation: long-term anticoagulation based on CHA2DS2-VASc score. LV thrombus: consider extended anticoagulation if LV function remains poor. LAA closure device consideration for patients who cannot tolerate anticoagulation.
When to Seek Immediate Care
Call 911 immediately for:
- Sudden weakness or numbness (possible stroke)
- Difficulty speaking or understanding speech
- Vision changes
- Severe headache
- Chest pain or pressure
- Shortness of breath
- Rapid or irregular heartbeat
Frequently Asked Questions
Is cardiac thrombus dangerous?
Yes, cardiac thrombus is dangerous because it can break loose and travel to the brain, causing stroke. LAA thrombus in atrial fibrillation carries 15-20% annual stroke risk without treatment. Prompt detection and anticoagulation significantly reduce this risk.
How is cardiac thrombus treated?
Cardiac thrombus is treated with anticoagulation (blood thinners). For LAA thrombus related to atrial fibrillation, warfarin or direct oral anticoagulants (DOACs) are used for at least 3 weeks before cardioversion. For LV thrombus, anticoagulation is typically continued for 3-6 months.
Will I need surgery?
Most cardiac thrombi are treated with anticoagulation alone. Surgery is rarely needed but may be considered for: large mobile thrombus with high embolic risk despite anticoagulation, thrombus associated with cardiac tumor, or during other cardiac surgery (e.g., maze procedure for AF).
Can I exercise with cardiac thrombus?
Activity restrictions depend on thrombus size and mobility. Small, sessile thrombus may allow light activity. Large, mobile thrombus typically requires activity restriction to reduce embolic risk. Follow your doctor's specific recommendations. Once thrombus resolves, normal activity can usually resume.
How long does it take for the clot to dissolve?
With adequate anticoagulation, most thrombi show partial resolution within 4-6 weeks and complete resolution by 3-6 months. Some thrombi may organize and become adherent to the wall, posing less embolic risk. Repeat imaging guides duration of therapy.
References
Medical References
This content is referenced from authoritative medical organizations:
- 1.ACR Appropriateness Criteria for Cardiac Thrombus Evaluation— American College of Radiology(2023)View
- 2.
Medical Disclaimer: This information is for educational purposes. Cardiac thrombus requires management by a cardiologist. Always seek emergency care for stroke symptoms.
Correlate with Lab Results
When Cardiac Thrombus on CT appears on imaging, doctors often check these lab tests:
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