ACQUIRED PERICARDIAL PATHOLOGIES SA-CME DETAILS ON PAGE 9 www.appliedradiology.com n 11 March–April 2021 on the underlying etiology; patients with neoplastic pericardial effusion generally have a poor prognosis, while those with idiopathic/viral pericarditis usually have a very good prognosis. 5 Pericardial Tamponade Pericardial tamponade is a life-threat- ening mechanical condition occurring when pericardial effusion increases pericardial pressure; thus, impairing diastolic filling of the heart. 12 This in- sufficiency leads to a decline in cardiac output and blood pressure. 13,14 Presen- tation may be either acute (with chest discomfort, dyspnea, and hypotension) or subacute (asymptomatic initially with gradual progression of symptoms). 12,13 A variety of pathologic conditions may re- sult in pericardial tamponade, including infection, inflammatory processes, ma- lignancy, and trauma. 12,14 Echocardiography is considered a sensitive and rapid diagnostic tool. 15 An increase in the right ventricle (RV) dimension and a decrease in the left ventricle (LV) dimension on inspira- tion is suggestive of pericardial tam- ponade. 11,16 Diastolic collapse of the compliant RV signifies that pericardial pressure exceeds early diastolic RV pressure. 11,14 Detection of RA collapse is 100% sensitive, but less specific, for tamponade. 11,16 LV collapse is less common, owing to its wall thick- ness. 11,16 Typical findings of pericardial tamponade on CT and MRI include flattening or inversion of the right atrial or RV wall with compression of these chambers, inversion of the interventric- ular septum, distention of the superior and inferior vena cavae, and reflux of contrast into the azygos vein and in- ferior vena cava. 14 These findings are better appreciated on electrocardio- graphically gated cardiac studies. The pericardial space in pericar- dial tamponade often requires urgent A B C FIGURE 1. Lateral (A) chest radiographic image shows the interface between low-density epicardial fat, the relatively higher-density pericardial effusion (arrow), and low-density pericardial fat (”Oreo cookie sign”). Four-chamber (B) cardiac MRI of a different patient shows intermediate signal epicardial fat sharply demarcated against the high-signal pericardial fluid (arrow). The inner visceral and outer parietal layers of the peri- cardium are appreciated as curvilinear low-intensity bands containing the high-signal fluid. Four-chamber (C) inversion recovery images null the fluid signal of the effusion, which now appears devoid of signal (black). A B C FIGURE 2. Short axis (A) steady state free precession MRI of the heart shows a band of irregular, intermediate-signal tissue (arrow) encasing the heart and representing irregular thickening of the pericardium. Heterogeneous signal of the fluid located between the visceral and parietal layers of the pericardium is consistent with exudative effusion. Corresponding short axis (B) and four-chamber (C) delayed-enhancement MR image shows linear enhancement of the pericardium (arrows) confirming active pericardial inflammation/infection.