A 75-year-old man with no significant past medical history presented with progressive dyspnea for one month. Upon presentation, he was found to be hypoxic with an oxygen saturation of 80%. His cardiac and pulmonary examinations were unremarkable. An arterial blood gas (ABG) showed pure hypoxia without hypercarbia. A chest x-ray was completely unremarkable. Due to concern for possible pulmonary embolism (PE), a CT scan with IV contrast was performed and was negative for PE; it also did not show any clear lung pathology. However, it did show a small pericardial effusion and pericardial calcifications.
Trans-thoracic echocardiography with agitated saline was then done to evaluate for possible shunting, and confirmed moderate shunting through a PFO. Right heart catheterization (RHC) was then performed and showed an equalization of diastolic pressures, as well as the characteristic "square root sign," consistent with constrictive physiology (Fig. 1).
Cardiac MRI was done for further classification, and did show a thickened pericardium with a small circumferential effusion and ventricular interdependence, confirming constrictive pericarditis. The workup for the etiology of his pericarditis was unremarkable, including negative autoimmune and tuberculosis testing.
The patient continued to be hypoxic, requiring oxygen by high-flow nasal cannula to maintain an adequate oxygen saturation. It was thought that the pericardial constriction was leading to elevated right heart pressures, and therefore the shunting and respiratory failure. The decision was made to undergo pericardiectomy, for which he was electively intubated. He underwent successful pericardiectomy with complete liberation of the bilateral anterior ventricles and 80% pericardial resection from the right atrium; certain areas of the ventricles (primarily the lateral and basilar walls of the left ventricle), the pericardium could not be completely removed and so was scored in a crosshatch pattern. After the procedure, he was unable to be weaned from the ventilator, and continued to require 100% FiO2. This indicated that the shunting was still ongoing through the PFO and causing hypoxia. The following day he underwent trans-esophageal echocardiography which again showed a moderate PFO with significant right-to-left shunting (Fig. 2).
The patient underwent another RHC which did show mildly elevated right sided filling pressures, continued equalization of right and left heart filling pressures with a restrictive right ventricular filling pattern, and significant right-to-left shunting (QP:QS = 0.86). He had successful trans-catheter placement of a PFO closure device. He was weaned from the ventilator and successfully extubated three days post-procedure, and discharged home several days later on room air. Repeat trans-thoracic echocardiography four months later did not demonstrate any shunting.