Pulmonary Embolism & Deep Vein Thrombosis
Pulmonary Embolism & Deep Vein Thrombosis
Overview
Pulmonary embolism occurs when the pulmonary arteries are obstructed.
This is most often due to emboli that travel from the deep veins of the thighs/pelvis.
Because deep vein thrombosis and pulmonary embolism so often occur together, we have a term for their combined condition: venous thromboembolism.
Nonthrombotic sources of pulmonary embolism include: air, fat, amniotic fluid, bacterial (septic), foreign bodies, and, tumors.
Pulmonary embolism is a leading cause of cardiovascular-related death; denote that key complications of pulmonary embolism include pulmonary hypertension, right heart failure, and pulmonary infarction.
Treatments:
Supportive therapy, which includes administration of oxygen, saline, and vasopressors.
Anti-coagulation therapies, which can include heparin or fondaparinux for short-term treatment, and warfarin for longer-term treatment.
In some cases, embolectomy or clot dissolution is required to restore blood flow through the pulmonary arteries.
Deep Vein Thrombosis
Virchow Triad
The "Virchow Triad" comprises three factors that predispose an individual to deep vein thrombosis; each of the three elements of the Virchow Triad contribute to the formation of clots in the blood vessels.
Endothelial injury promotes clotting – endothelial injury can be due to fracture, surgery, trauma, or even previous deep vein thrombosis.
Upon injury, the endothelium responds by triggering the clotting cascade (review of hemostasis). If this process goes unchecked, and the clots are not ultimately dissolved, they can be problematic.
Venous stasis is another predisposing factor – venous stasis can be caused by immobility (if a person is bed-ridden or on a long flight, for example), elevated central venous pressure, heart failure, and obesity.
To prevent DVT in hospitalized patients, we use SCD's (sequence compression devices), which prevent venous stasis in the legs.
In select patients, we use prophylactic anticoagulants, which includes low doses of enoxaparin or heparin.
Note that heparin-induced thrombocytopenia is a worrisome complication of anticoagulant, but, overall, in the correct population, prophylactic anticoagulants can be an important way of preventing DVT.
Hypercoagulation states
– Pregnancy (which is also associated with inferior vena cava stasis)
– The post partum period
– Smoking (which is also associated with endothelium damage)
– Cancer
– Medications, including combined hormonal contraceptives and some hormonal replacement therapies
– Coagulation disorders, such as Factor V Leiden disorder.
Be aware that individuals with multiple predisposing factors (i.e., pregnant women who are put on bed rest, for example), are at higher risk for developing deep vein thrombosis.
Symptoms
When present, symptoms of deep vein thrombosis tend to arise unilaterally in the legs, leaving them swollen, tender, and with signs of venous dilation.
Deep vein thrombosis can occur in the upper body, too, but this is less common.
Post thrombotic syndrome occurs when the venous valves are damaged.
Diagnosis of deep vein thrombosis:
Wells Score for Deep Vein Thrombosis, which gives points based on several factors including the presence of swelling, edema, and the likelihood of alternative diagnosis.
(see the link in our notes for a full description of the Wells Score for Deep Vein Thrombosis).
D-dimer level is an important way to try to rule out low-probability DVTs.
If deep vein thrombosis is highly suspected, imaging with contrast venography or venous ultrasonography with compression can verify the presence of thrombus.
Pulmonary Embolis
- Ventilation to perfusion scan is a noninvasive test that can indicate the presence of a blood clot.
For references, please see full tutorial on PE and DVT.