Ecase 5/17/2001

Tim Lee, MD

• HPI: 41 year old woman presented to clinic with a several month history of intermittent pleuritic pain in her right upper quadrant, right chest, and right shoulder. She also had some associated dyspnea and chest tightness with these episodes. She attributed her symptoms to eating and wondered about having possible gallbladder disease.

• PMH: She has H/o positive Hep B surface ag and liver cysts on ultrasound. Negative Hep B e-antigen.History of left ankle surgery 4 years ago.History of subserosal myomas on ultrasound.Gravida 1, para 0, with a miscarriage in Feb 2000 and a D&C.She denies smoking.

• Meds: Oral contraceptive

• EXAM: Vitals stable. O2 sat 96% at rest and dropped to 92% with exertion. Her pulse rose to 120 with exertion

• CHEST: clear, nontender to palpation.

• CV: RRR without murmur

• ABD: benign, no masses

• EXT: negative.

• CXR negative.

What screening test for pulmonary embolus would you check in this patient?

What is the relationship between oral contraceptive agents and activated protein C resistance?

What screening test for pulmonary embolus would you check in this patient?

V/Q lung scan remains the most useful screening test to rule out acute pulmonary embolism. Normal or high probability scans are extremely helpful. Nondiagnostic are difficult to interpret especially in this patient who I would say had a moderate to high clinical suspician of pulmonary embolism.

If the clinical likelihood is low, a d-dimer ELISA and venous ultrasonography may be useful. Because the d-dimer ELISA lacks specificity and levels of d-dimer are elevated in patients with myocardial infarction, pneumonia, heart failure, or cancer and in those who have undergone surgery, the assay is best suited for patients without other systemic illnesses. Spiral CT of the chest with contrast is best suited for identifying pulmonary embolism in the proximal pulmonary vascular tree. If the CT findings are normal in the presence of a high index of clinical suspicion, pulmonary angiography that focuses on the distal pulmonary vasculature should be performed.

What is the relationship between oral contraceptive agents and activated protein C resistance?

Activated protein C is the most potent endogenous anticoagulant. Activated protein C inactivates coagulation factor V. A point mutation (the factor V Leiden mutation) in the gene coding for coagulation factor V is responsible for activated protein C resistance. Resistance to this protein is considered to be present when challenge with activated protein C prolongs the PTT in plasma less in patients than in control subjects. This appears to be inherited as an autosomal dominant trait. Use of oral contraceptive agents and pregnancy increase the frequency of activated protein C resistance even in women without the factor V Leiden mutation. Women with factor V Leiden who use oral contraceptive agents have an estimated 35-fold increase in the risk of venous thromboembolism, as compared with women without the mutation.

In this patient a V/Q scan showed a V/Q mismatch in lingula c/w intermediate probability (30-40%) of pulmonary embolism. Bilateral LE venous doppler study negative. Pulmonary angiogram showed extensive large bulky defect in left main and multiple branches of left lower pulmonary artery c/w acute pulmonary emboli. She was admitted and treated. In the hospital, tests for Anti-thrombin III, protein C and S, lupus anticoagulant, and factor V Lieden were all normal.

Reference

Goldhaber: Medical Progress: Pulmonary Embolism; NEJM, Vol 339, July 9, 1998. 93-104