This is a report of a patient presenting with a hematoma compressing the right atrium in the immediate post-operative period and the diagnosis by echocardiography allowed prompt surgical treatment with reversibility of the hemodynamic failure. Echocardiography is an important tool in the diagnosis of post-operative complications and transesophageal echocardiography can be very helpful in this setting, where technically difficult transthoracic exams are the rule.