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5. Right heart catheterization
Inspiratory and expiratory chest radiography can be useful for detecting pneumothorax and for exposing air trapping in patients with large and/or small airway obstruction, but likely will not benefit this patient because the thoracic CT already obtained would have disclosed any pneumothorax overlooked at initial chest radiography, and airflow obstruction was not seen at the V/Q study already obtained. 68Ga-citrate scanning can occasionally be useful for evaluation of patients with diffuse lung disease, but no such findings are evident at the recent pulmonary CTA study. There is no clear lung parenchymal target for bronchoscopy. Similarly, there is no clear abnormality to evaluate with 18FDG-PET scanning. Right heart catheterization is indicated, given the features suggesting elevated pulmonary arterial pressure at both echocardiography and pulmonary CTA, but without an explanation provided by these studies.
The patient underwent right heart catheterization which showed a mean pulmonary artery pressure of 36 mmHg, wedge pressure of 8 mmHg, central venous pressure of 7 mmHg, and pulmonary vascular resistance between 5-8 Wood units. The findings were interpreted as consistent with World Health Organization Group I pulmonary hypertension with reduced cardiac output, although a Group IV etiology was not excluded. No left-to-right shunt was noted. The pulmonary hypertension was thought to perhaps be related to an as yet undiagnosed autoimmune disease. Her platelet count had decreased over the previous 2 days since admission from to 183 x 123 x 109 cells/L and then to 69 x 109 cells/L 4 days later. The consulting rheumatologist felt a rheumatological disorder was not a likely explanation for the patient’s condition. Her peripheral blood smear showed schistocytes, which prompted consideration for thrombotic thrombocytopenic purpura.
Which of the following is the most likely consideration for the patient’s condition given the data thus far? (Click on the correct answer to procced to the sixth and last panel)