A 33-year-old female with carcinoid heart disease and a 27-mm Medtronic-Hall tricuspid valve prosthesis presented with dyspnea 2 weeks after abdominal surgery. Initial transthoracic echocardiography (TTE) demonstrated a 6–mm Hg diastolic gradient and appropriate opening and closing of the prosthetic valve (A; Online Videos 1A and 1B). Within hours, the patient required intubation for hypoxemia. Invasive hemodynamic assessment revealed a central venous pressure (CVP) of 30 mm Hg with a biphasic dip and rise every 5 to 7 cardiac cycles (B). Arterial blood pressure varied inversely with the CVP. The suspected diagnosis of an intra-atrial shunt causing hypoxemia (C; Online Video 2) secondary to intermittent obstruction of the prosthetic valve (D; Online Video 3) was confirmed by using 2-dimensional transesophageal echocardiography and pulsed-wave Doppler imaging. Valve opening corresponded to an accentuated x descent, v wave, and y descent in the CVP tracing. A thrombus was seen in the right atrium (RA) (C; Online Video 2), and thrombolytic therapy resolved the valve dysfunction, CVP overload, and hypoxemia. LA = left atrium; RV = right ventricle; SVC = superior vena cava.