We present a rare complication after open-heart surgery resulting in compression of the superior vena cava (SVC) with the concurrent findings of the hypertrophic obstructive cardiomyopathy physiology. A 59-year-old woman developed a low cardiac output syndrome, persistent hypotension, and increasing filling pressures after emergency replacement of the ascending aorta and resuspension of the aortic valve due to a type A aortic dissection. Transesophageal echocardiography (TEE) evaluation revealed partial SVC obstruction, under-filled left ventricle (LV), and a persistent mitral systolic anterior motion with increasing pressure gradient in the left ventricular outflow tract (LVOT). Surgical exposure uncovered an intrapericardial thrombus around the aortic graft compressing the SVC. Removal of the thrombus resulted in immediate haemodynamic improvement and elimination of both SVC and LVOT obstructions. A comprehensive TEE exam should always be performed, and all the structures should be visualized for the proper diagnosis and management of patients after cardiac surgery.