Unclogging the Mystery: Can Advanced Imaging Spot Blood Clots That Will Dissolve?
"A new MRI technique shows promise in predicting which deep vein thrombi will respond to clot-busting treatment, potentially saving patients from unnecessary risks."
Deep vein thrombosis (DVT), the formation of blood clots in the deep veins of the legs, is a serious condition. If left untreated, DVT can lead to pulmonary embolism (PE), a life-threatening blockage in the lungs. Current treatment strategies often involve catheter-directed thrombolysis (CDT), a procedure where clot-dissolving drugs are delivered directly to the thrombus.
However, CDT isn't always successful and carries significant risks, including bleeding complications. Determining which patients will benefit from CDT and who might be better served by alternative therapies remains a challenge. Thrombus age, often based on patient history, is an unreliable indicator, and a more precise way to assess clot composition is needed.
Now, a new study presented at the 19th Meeting of the European Venous Forum offers a promising solution. Researchers have successfully translated a non-contrast Magnetic Resonance Imaging (MRI) technique, previously tested in animal models, into a clinical setting to predict thrombus lysability – the likelihood of a clot to dissolve with treatment.
Current DVT Care
Venous thromboembolism includes pulmonary embolism, which can be fatal and cause chronic thromboembolic pulmonary hypertension, and deep vein thrombosis, which can cause leg swelling and postthrombotic syndrome. VTE may also develop in splanchnic veins and other atypical locations. Medscape reports that most DVT is occult and resolves spontaneously without complication, although massive pulmonary embolism associated with DVT causes as many as 300,000 deaths annually in the United States; ASH reviewed its treatment guidelines in August 2022.
A Long Medical History
Historical reviews trace the evolution of DVT treatment across roughly seven centuries, including the development and abandonment of particular treatments, caval filtration, and endovascular therapies. One review identifies 1271 as the date of the first well-documented case, when Raoul developed unilateral ankle edema that extended to the leg. Later historical work notes that direct oral anticoagulants were still an emerging topic in the 2013 review and were examined more fully twelve years later.
MSTI: A New Window into Thrombus Composition
The study, led by Justinas Silickas and colleagues from King's College London, explored the use of multi-sequence thrombus imaging (MSTI) in patients with acute iliofemoral DVT (clots in the iliac and femoral veins). MSTI involves a specialized MRI protocol that assesses various characteristics of the thrombus, including:
- T1 Mapping: Measures the relaxation times of water molecules within the thrombus, providing information about its age and composition.
- Magnetization Transfer: Assesses the interaction between water and macromolecules in the thrombus, reflecting its structural integrity.
- Diffusion-Weighted Imaging: Measures the movement of water molecules, indicating the density and organization of the thrombus.
Imaging Performance and Practice
Compression ultrasonography is reported to have 97% sensitivity and 94% specificity for diagnosing symptomatic femoro-popliteal DVT in the general population. Comparative reviews also examine how patients are managed in routine practice versus the recommendations of published clinical guidelines. More recent international guidance reviews report that important differences persist among guidelines despite broad agreement that acute DVT remains a major cause of morbidity and mortality.
Personalized DVT Treatment on the Horizon?
This study demonstrates the potential of MSTI to identify patients with iliofemoral DVTs who are most likely to respond to thrombolysis. By using cut-off values for T1 relaxation time, MTR, and ADC, the researchers achieved a sensitivity of 89% and specificity of 100% in distinguishing lysed and non-lysed thrombi. This suggests that MSTI could be used to stratify patients for CDT, avoiding unnecessary risks and costs in those unlikely to benefit. The researchers emphasize the need for further optimization of image analysis methods and validation of these findings in collaboration with other centers. However, this study represents a significant step towards personalized DVT treatment, potentially improving outcomes and reducing complications for patients with this common and potentially life-threatening condition.
Toward More Personalized Care
Recent overviews describe advances in DVT diagnosis, treatment, and prevention, including new pharmacological and interventional therapies. One future-focused review specifically highlights artificial intelligence, novel biomarkers, pharmacological therapies, and interventional devices. Another reports that integrating emerging trends into clinical practice may support more personalized, effective, and sustainable DVT management and reduce its long-term burden.
Why DVT Remains Difficult
Altered hemodynamics, hypercoagulability, and damaged vascular tissue contribute to DVT and pulmonary embolism, while venous valves are considered likely sites for initial clot formation. However, the exact pathway by which thrombosis develops in that environment is not entirely clear. DVT is also described as an under-recognized public health issue in Africa, where limited awareness, diagnostic challenges, and resource limitations remain concerns.
Treatment in Real-World Patients
Catheter-directed thrombolysis is described as a primary interventional treatment for DVT and includes pharmacomechanical and rheolytic therapies. The prospective, multicenter, industry-sponsored ClotTriever Outcomes registry analyzed its first 250 patients to assess the safety and effectiveness of mechanical thrombectomy for acute, subacute, and chronic DVT. These categories show why real-world treatment strategies must account for differences in thrombus chronicity.