Why is it important to look for Deep Vein Thrombosis (DVT) in extremities when diagnosed with Pulmonary Embolism (PE)?

Importance of Looking for DVTs in Extremities When Diagnosed with Pulmonary Embolism

Looking for deep vein thrombosis (DVT) in the extremities when a patient has been diagnosed with pulmonary embolism (PE) is crucial because PE originates from a lower limb DVT in approximately 90% of cases, and finding a residual DVT helps guide treatment decisions, prevent recurrence, and identify patients at higher risk for complications.

Pathophysiological Connection Between DVT and PE

PE and DVT are different clinical manifestations of the same disease entity - venous thromboembolism (VTE). The relationship between these conditions is well-established:

• Autopsy studies have confirmed that PE arises from a lower limb DVT in 90% of patients 1
• When venography is systematically performed in patients with angiographically confirmed PE, a residual DVT is found in approximately 70% of cases 1
• In most cases, PE is a direct consequence of DVT, with thrombi breaking off and traveling to the pulmonary circulation 1

Diagnostic Value of Finding DVT

Finding a DVT in a patient with suspected PE has significant diagnostic value:

• Compression ultrasonography (CUS) shows a proximal DVT in 30-50% of patients with confirmed PE 1
• Finding a proximal DVT in patients suspected of having PE is considered sufficient to warrant anticoagulant treatment without further testing 1
• CUS has a high diagnostic specificity (96%) for PE when positive, though sensitivity is lower (41%) 1
• In patients with contraindications to CT imaging, finding a DVT can establish the diagnosis of VTE without exposing the patient to radiation 1

Impact on Treatment Decisions

Identifying a DVT in a patient with PE influences treatment decisions in several ways:

• Patients with both PE and DVT may require more aggressive or prolonged anticoagulation therapy 1
• The presence of a proximal DVT increases the risk of recurrent VTE in patients with PE 1
• Patients in whom PE is confirmed by the presence of a proximal DVT should undergo risk assessment for PE severity and early death risk 1
• Serial leg testing may replace angiography in patients with non-diagnostic lung scan findings 1

Prevention of Recurrence and Complications

Identifying and treating DVT in PE patients helps prevent serious complications:

• Untreated DVT can lead to recurrent PE, which has a higher mortality rate than the initial event 1
• Recurrent episodes are about three times more likely to be PE after an initial PE than after an initial DVT 1
• Finding and treating DVT reduces the risk of post-thrombotic syndrome, a chronic complication of DVT 1

Practical Approach to DVT Detection in PE Patients

The American Society of Hematology and European Society of Cardiology recommend:

• In the setting of suspected PE, compression ultrasonography can be limited to a simple four-point examination (bilateral groin and popliteal fossa) 1
• The only validated diagnostic criterion for DVT is incomplete compressibility of the vein 1
• The probability of a positive proximal CUS in suspected PE is higher in patients with signs and symptoms related to the leg veins than in asymptomatic patients 1

Pitfalls and Caveats

• A normal ultrasonography exam of the leg veins does not rule out PE due to limited sensitivity 1
• CUS cannot completely rule out DVT because these tests are not sensitive for distal (calf-vein) DVT 1
• Excessive pressure when performing ultrasonographic studies should be avoided as clot embolization is a rare but potential complication that can lead to PE 2
• Upper extremity DVT, though less common than lower extremity DVT, can also cause PE and should be considered, particularly in patients with central venous catheters 3

In conclusion, looking for DVTs in extremities when a patient has PE is an essential part of comprehensive management that helps establish diagnosis, guide treatment decisions, prevent recurrence, and identify patients at higher risk for complications.