A 46-year-old woman was admitted to our hospital with decompensated congestive heart failure and pericardial effusion diagnosed on echocardiography. She had no family history of sudden cardiac death. She was born at term and experienced no cardiac events until 4 years of age, at which point she was hospitalized because of three syncopal episodes that were not related to exercise. Over the next 10 years, she experienced two additional episodes of syncope not related to exercise. She had another hospital admission at 12 years of age. Clinical examination did not reveal cyanosis or clubbing, peripheral pulses were normal, and blood pressure was 90/60 mmHg. Her venous pressure was elevated, but the liver was not enlarged, and the lung fields were clear. Electrocardiography showed sinus rhythm, right bundle branch block, T -wave inversion in V6, and evidence of right atrial dilatation. T wo-dimensional echocardiography showed normal intracardiac connections, with the tricuspid valve in the normal position and normal size of the left atrium and left ventricle with a normal ejection fraction. The right ventricle was dilated without evidence of right ventricular outflow tract obstruction. Implantation of an implantable cardioverter-defibrillator was considered but was ultimately contraindicated because of right ventricle anatomy. Thus, the patient received conservative care and was started on digoxin and diuretics. At 32 years of age, she experienced an episode of atrial flutter that was treated with electrical cardioversion. As stated earlier, at 46 years of age, she was admitted to our hospital with decompensated heart failure to be evaluated for a heart transplant. She underwent electrocardiography, echocardiography, cardiac MRI with and without administration of contrast media, and non–cardiac-gated multidetector CT with and without contrast media to rule out pulmonary embolism. The following quantitative results were obtained with MRI: Left ventricular end-diastolic volume (LVDV) was 40 mL (LVDV per body surface area [BSA], 25 mL/m2); left ventricular end-systolic volume (LVSV), 21 mL (LVSV/ BSA, 13 mL/m2); stroke volume (SV), 19 mL (SV/BSA, 12 mL/m2); and ejection fraction, 47%. Right ventricular end-diastolic volume (RVDV) was 262 mL (RVDV/BSA, 164 mL/m2); right ventricular end-systolic volume (RVSV), 198 mL (RVSV/BSA, 124 mL/m2); stroke volume (SV), 64 mL (SV/BSA, 40 mL/m2); and ejection fraction, 24%. Phase contrast sequences in the aorta and pulmonary artery showed systemic output of 20 mL and pulmonary output of 18 mL. T ricuspid regurgitation was massive (46 mL) (Figs 1–4).Posteroanterior chest radiography showed severe cardiac enlargement. Electrocardiography showed atrial flutter (ventricular rate, approximately 90 beats per minute), fragmented QRS complex with diffuse low voltage, and no specific ST depression (Fig 1). Cardiac MRI unenhanced short-axis (Fig 2, A) and four-chamber cine steady-state free precession imaging (Fig 2, B) showed severe enlargement of the RV; the RV free wall myocardium was extremely thinned, the apical trabeculation was almost absent, and the wall was irregular with a parchmentlike appearance. Thrombus was seen in the RV outflow tract. The severe enlargement of the RV resulted in decreased size and d-shape morphology of the left ventricle, which has normal myocardium. The tricuspid valve was seen in its normal position. The right atrium was dilated and hypertrophied. Pericardial effusion also was noted. Cardiac unenhanced four-chamber T1-weighted blackblood inversion recovery MRI sequences without fat saturation did not show fatty infiltration of the right myocardium (Fig 2, C). Cardiac radial axis fast gradient-echo inversion-recovery MRI sequences performed 8–10 minutes after contrast media injection (late enhancement technique) showed diffuse late enhancement in the right atrial and ventricular walls. Thin thrombus was also seen in the RV apex (Fig 3, A–D). The presence of thrombus in the RV identified on cardiac MRI scans prompted further investigation with non– cardiac-gated MDCT with and without contrast enhancement to rule out pulmonary embolism. Intravenous contrast-enhanced MDCT axial images enabled confirmation of severe enlargement of the right cardiac chambers with left-sided deviation of the interventricular septum, decreased size, and d-shape morphology of the left ventricle (Fig 4, A). In the RV outflow tract, chronic thrombus with calcification was seen (Fig 4, B). No fatty infiltration was identified in the RV (Fig 4, A and B). Anomalous insertion of the tricuspid valve was excluded (Fig 4, A). On volume-rendering reconstructed CT images, no pulmonary venous anomalous drainage was seen (Fig 4, C). No pulmonary embolism was identified. In this case, the diagnosis of Uhl anomaly was made when the patient experienced syncopal episodes unrelated to exercise at 4 years of age. The diagnosis was made based on clinical history and electro- and echocardiographic findings. The patient was admitted to our hospital much later with signs and symptoms of congestive heart failure, a large pericardial effusion amenable to percutaneous drainage, and for evaluation for heart transplantation. Until this episode, the patient had received conservative care since implantable cardioverterdefibrillator implantation was contraindicated, and she had previously refused heart transplantation. During her most recent hospitalization (presented in the History of this case), electrocardiography, echocardiography, cardiac MRI and, non–cardiac-gated MDCT with and without administration of contrast media were performed. Clinical history and cardiac morphologic changes on echocardiograms and cardiac MRI and MDCT images enabled us to confirm the diagnosis of Uhl anomaly. The patient is still alive and awaiting heart transplantation. What is your diagnosis?