Correct!
2. The 133Xe-ventilation – 99mTc-perfusion scintigraphy shows findings suggesting pulmonary embolism
The 133Xe-ventilation – 99mTc-perfusion scan shows relatively normal perfusion bilaterally but with multiple areas of clear perfusion defects, representing “mis-matched” ventilation and perfusion, consistent with pulmonary embolism. The scan is abnormal, and, while the presence of ventilation and perfusion mis-matching is not entirely specific for pulmonary embolism, the scan is suggestive of that disorder and therefore is not merely non-specifically abnormal. The “stripe sign” at 133 Xe-ventilation – 99m Tc-perfusion scintigraphy represents a rim of tracer uptake peripheral to a perfusion defect, indicating that lung is present between a defect and the pleura, which is not a pattern consistent with pulmonary embolism and indicates a non-embolic cause for a perfusion abnormality- perfusion defects related to pulmonary emboli extend to the lung periphery. The 133Xe-ventilation – 99mTc-perfusion scan does not show features indicating systemic shunting- this situation is indicated by tracer uptake in the kidney or brain, neither of which are seen in Figure 3.
The 133Xe-ventilation – 99mTc-perfusion was interpreted as “high probability” for pulmonary embolism. Because the patient’s clinical history indicated a prolonged course for the development of her shortness of breath, and she had no known thromboembolic risk factors, the pre-test probability for acute pulmonary embolism was estimated as low. Therefore, the possibility of chronic thromboembolic disease was considered.
Which of the following represents the most appropriate next step for the management of this patient? (Click on the correct answer to proceed to the sixth of nine pages)