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Thromboembolic disease is the leading non-obstetrical cause of maternal mortality, with an incidence of 0.05-0.3%. Early recognition and proper treatment dramatically improves outcome.
The risk of thromboembolism during pregnancy and the postpartum period is 5.5 times greater than that for nonpregnant patients.
Twenty four percent of untreated patients with deep venous thrombosis will have a pulmonary embolism, with a mortality rate of 15%. If treated with anticoagulants, embolization will occur in only 4.5%.
The risk of thromboembolism is increased during pregnancy because the gravid uterus impairs the velocity of venous flow from the lower extremities.
The risk of thromboembolism increases nine-fold with cesarean delivery as compared with vaginal delivery.
Diagnosis
A. Deep Venous Thrombosis
1. DVT most commonly manifests as pain and swelling. The physical exam may reveal tenderness, a difference in leg circumference, redness, and a positive Homan's sign. None of these signs or symptoms is specific, and DVT may also be completely asymptomatic.
2. Venography is an invasive procedure, and the contrast material can cause chemical phlebitis. Venography is useful when the results of other studies are equivocal.
3. Doppler ultrasound is the diagnostic study of choice in cases of suspected DVT. The sensitivity is 91% and specificity is 99%. When clinical findings are inconsistent with Doppler studies, venography is necessary.
4. Impedance plethysmography is an alternative technique for DVT diagnosis. Venous return in the lower extremity is occluded by inflation of a thigh cuff, and then the cuff is released, resulting in a decrease in calf blood volume. Any obstruction of the proximal veins diminishes the volume change, which is detected by measuring changes in electrical resistance (impedance) over the calf.
B. Pulmonary Embolism
1. Pulmonary embolism most frequently presents with dyspnea and tachypnea. Cough, hemoptysis, and pleuritic chest pain may sometimes occur.
2. Physical exam may reveal only tachycardia or a few crackles. Massive pulmonary embolism may cause hypotension, syncope, right-sided heart failure with jugular vein distention, hepatomegaly, left parasternal heave, and fixed splitting of the second heart sound.
| Clinical Findings in Pulmonary Embolism | |
| Clinical Finding | Pulmonary Embolism (%) |
|
Tachypnea
Dyspnea Pleuritic pain Apprehension Cough Tachycardia Hemoptysis Temperature >37°C |
89
81 72 59 54 43 34 34 |
C. Laboratory Studies
1. Electrocardiography is abnormal in 90% of pulmonary embolisms; tachycardia is the most common abnormality. Nonspecific T-wave inversions occur in 40%; right axis shift with strain pattern occurs with large embolisms.
2. Arterial Blood Gases. A pulmonary embolism is unlikely with a PaO2 of >80 mm Hg on room air. However, 11.5% of patients with pulmonary embolism have a PaO2 of 80-90 mm Hg.
3. Technetium Lung Scanning
a. The perfusion scan is performed first, and a normal scan excludes pulmonary embolism. If the perfusion scan is abnor mal, a ventilation scan is completed. Matching ventilation perfusion defects are not suggestive of embolism.
b. Almost all patients with pulmonary embolism have abnormal V/Q scan results (high, intermediate, or low probability). Unfortunately, most patients without emboli also have abnormal results (sensitivity 98%, specificity 10%). When clinical suspicion does not correlate with results of lung scanning, pulmonary angiography is necessary.
4. Coagulation Studies. If a family history of repeated is present, antithrombin-III, protein C.