Natural History of Isolated Deep Vein Thrombosis of the Calf

Study Overview
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Brief Summary
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Whether isolated distal DVT (IDDVT), DVT confined to the calf, should be looked for and diagnosed to allow them to be treated with anticoagulants remains one of the still unsolved issues in vascular medicine, especially because of the insufficient data on clinical risks of untreated distal DVT. Management studies have shown that it is safe to withhold anticoagulation in outpatients with suspected DVT if compression ultrasonography (CUS) limited to the proximal deep veins yields normal results on presentation and on repeated examination after 5 to 7 days. This strategy is based on the premise that IDDVT do not need to be diagnosed and treated, what is necessary when they extend involving the proximal veins. There is no general agreement, however, on the assumption that the non-extending IDDVT do not need to be diagnosed and treated, and many authors recommend to perform a single CUS examination extended to the distal deep veins. All the available studies have treated with anticoagulants the diagnosed IDDVT and no adequate information is available on the risk of IDDVT left untreated. The present study, performed in outpatients with suspected leg DVT, aims at assessing the clinical consequences of IDDVT diagnosed (by a complete US investigation) but not treated because the results of this investigation remain blind to both the patient and the treating doctor, whereas the diagnostic-therapeutic procedure remains the usual one, based on CUS investigation limited to diagnose proximal DVT, to be repeated after 5-7 days (or earlier) to exclude an extension to proximal veins of an IDDVT potentially present.

Detailed Description
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Outpatients symptomatic for suspected DVT of a leg are examined by a vascular doctor according to standard procedure based on pre-test clinical probability (PTCP) assessment, D-dimer assay and a CUS limited to the proximal deep veins. Those in whom a proximal DVT is excluded and have intermediate/high PTCP or altered D-dimer level are eligible for the study. The included patients are immediately submitted to an extensive echo-color-Doppler examination of calf deep veins by a different vascular doctor and results are closed in an envelope that will be open after three months (or before if necessary). In the meantime, patients will follow the standard diagnostic procedure: they receive an appointment to come back in 5-7 days for a further CUS examination, or even before in case of worsening of symptoms/signs. All the included patients receive a telephone call after three months to exclude possible complications.

Official Title
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Diagnosis and Evolution of Isolated Deep Vein Thrombosis of the Calf in Symptomatic Outpatients. The Blind, Prospective CALTHRO Study.

Conditions
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Isolated Distal DVT, Proximal DVT, Pulmonary Embolism

Intervention / Treatment
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* Other: Ultrasound examination of leg veins


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: suspected deep vein thrombosis of a leg intermediate/high pre-test clinical probability or high D-dimer levels Exclusion Criteria: age < 18 years presence of proximal DVT suspected isolated iliac DVT symptoms/signs lasting from > 30 days presence of symptoms of pulmonary embolism pregnancy or puerperium full dose treatment with heparin or derivatives from > 1 day presence of superficial vein thrombosis limited life expectancy (< 6 months) geographically inaccessible location inability or refusal to give consent participation in other clinical studies

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| 1<br>Outpatients with suspected leg DVT after exclusion of proximal DVT | Other: Ultrasound examination of leg veins<br>* Outpatients symptomatic for leg DVT follow the standard diagnostic procedure (ultrasound examination of proximal deep veins, pre-test clinical probability and D-dimer, and a second US after 5-7 days) to exclude proximal DVT; they also receive by another doctor a complete US examination of the deep leg veins to assess the presence of isolated calf DVT, the results of the latter examination are kept blind to the patient and to the treating doctor, and disclosed after three months<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Thrombotic complications (deep vein thrombosis and/or pulmonary embolism within three months from first examination |  | three months from first examination | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| other vascular complications; how many isolated distal DVT will be diagnosed |  | three months from first examination | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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distal DVT, calf DVT, DVT diagnosis, management of patients with suspected leg DVT