We present the case of a 64 year-old patient in whom an aortic Saint Jude prosthesis, a Cosgrove's mitral annulus and triple coronary artery by-pass graft were implanted, and who presented with shock related to extrinsic compression of the right atrium by a mediastinal hematoma within the first postoperative month. Transthoracic echocardiogram showed a right atrial <<Pseudo-mass>>, hampering right atrium drainage. The extrapericardial location of the hematoma is of note and was diagnosed with the aid of thoracic computerized tomography. We present the case of a 64 year-old patient in whom an aortic Saint Jude prosthesis, a Cosgrove's mitral annulus and triple coronary artery by-pass graft were implanted, and who presented with shock related to extrinsic compression of the right atrium by a mediastinal hematoma within the first postoperative month. Transthoracic echocardiogram showed a right atrial <<pseudo-mass>>, hampering right atrium drainage. The extrapericardial location of the hematoma is of note and was diagnosed with the aid of thoracic computerized tomography.