Pulmonary embolism

What to diagnose Pulmonary Embolism??

PE   is  the leading cause of maternal mortality in developed countries. The risk of PE is greatest immediately postpartum, particularly after cesarean delivery, with a fatality rate of nearly 15%. PE most commonly originates from DVT in the lower extremities, occurring in nearly 50% of patients with proximal DVT. Symp­toms typically associated with PE are all common in pregnancy, such as shortness of breath, chest pain, cough, tachypnea, and tachycardia. Because of the serious potential consequences of PE and the increased incidence in pregnancy, clinicians must have a low threshold for evaluation. Diagnosis starts with a careful history and physical examination, followed by diagnostic tests to rule out other possible etiologies, such as asthma, pneumonia, or pulmonary edema.

• Tests A) An arterial blood gas (ABG), electrocardiogram, and chest x-ray should be performed. ABG values are altered in pregnancy and must be interpreted using

pregnancy-adjusted normal values. More than half of pregnant women with a documented PE have a normal alveolar-arterial gradient.A chest x-ray helps rule out other disease processes and enhances interpretation of the ventilation-perfusion (V/Q) scan. The risks associated with various radiologic tests indicated for PE workup are minimal compared with the consequences of a missed PE.

Tests B:--Pulmonary angiography  is not usually doe  though  this is the gold standard for PE diagnosis, but it is expensive and invasive.

 Tests C : CT  Angio:-- Computed tomographic (pulmonary) angiography (CTA) is becoming the recommended imaging test in pregnant women with suspected PE. CTA is easier to perform, more readily available, more cost-effective, and provides a lower dose of radiation to the fetus than a V/Q scan. CT Angio  is also useful in detecting other abnormalities that may be contributing to the patients symptoms (e.g., pneumo­nia, aortic dissection). Newer technology, multidetector computed tomography pulmonary angiography, allows visualization of finer pulmonary vascular detail and provides greater diagnostic accuracy.

, Tests D:  the V/Q scan has been the primary diagnostic test for PE. It is interpreted as low, intermediate, or high probability for PE. High-probability scans (i.e., segmental perfusion defect with normal ventilation) confirm PE, with a positive predictive value over 90% when pretest likelihood is high. V/Q scans are limited in their usefulness because of the large proportion of indeterminate re­sults. Most fetal radiation exposure occurs when radioactive tracers are excreted in the maternal bladder. Therefore, exposure can be limited by prompt and frequent voiding after the procedure. If patient is postpartum and breast-feeding, breast milk should not be used for 2 days after a V/Q scan.

Tests E: Bilateral venous duplex imaging of the lower extremities                      If a pregnant woman has a nondiagnostic lung scan, bilateral venous duplex imaging of the lower extremities is recommended to evaluate for DVT. If DVT is found, PE can be diagnosed. If no DVT is seen, arteriography may be performed for further evaluation before a commitment to long-term anticoagulation is made, or venous duplex imaging may be repeated in 1 week.

 How safe is radiation?? According to the Centers for Disease Control and Prevention, in all stages of gesta­tion, a dose of <5 rads (0.05 Gy) represents no measurable noncancer health effects. After 16 weeks’ gestation, congenital effects arc unlikely below 50 rads. The risk for childhood cancer from prenatal radiation exposure is 0.3% to 1% for 0 to 5 rads. Any of the proposed modalities for diagnosis of PE are well below the dose levels that in­crease congenital abnormalities. Radiation exposure from a two-view chest radiograph is <0.001 rad. A higher dose of fetal radiation is provided with V/Q scan (0.064 to 0.08 rad) compared with CTA (0.0003 to 0.0131 rad). Pulmonary angiography provides approximately 0.2 to 0.4 rad with the femoral approach and <0.05 rad with the brachial approach. Maternal radiation dose is higher with CTA than V/Q scan.