eComment. Cardiac tamponade as a manifestation of acute mediastinitis

Valenzuela and colleagues [1] report a case of a 53-year old woman with an iatrogenic right coronary artery dissection, who underwent an urgent off-pump coronary artery bypass grafting to the right coronary system. One week later, she was operated on for a compressive purulent pericardial effusion without signs of wound infection. Unfortunately, she died because of therapy-refractory multiorgan failure. This report highlights the difficulty in making a timely diagnosis of this particular condition. Post-sternotomy mediastinitis is an ominous complication carrying a high risk of in-hospital mortality. An abundance of risk factors for the development of anterior mediastinitis has been identified and classified as preoperative (morbid obesity, osteoporosis, chronic obstructive pulmonary disease, diabetes, Staphylococcus-positive nasal swab, mediastinal radiotherapy and immunosuppressive intake), intraoperative (break in sterility, paramedian sternotomy, bone fracture with sternal retractor, technical mistakes in sternal closure, bilateral harvesting of thoracic arteries and prolonged operative time) and postoperative factors (prolonged time on ventilator and acute delirium syndrome) [2-4]. Despite regular use of prophylactic intravenous antibiotics and preventive measures, post-sternotomy mediastinitis occurs in a significant number of patients undergoing cardiac surgery. The Centers for Disease Control definition for surveillance of surgical site infections identifies three categories of surgical site infection [5]: superficial incision surgical site infection, deep incision surgical site infection and organ surgical site infection. According to the preceding definition, the in-hospital acquired infection of the retrosternal/mediastinal space of this patient without incisional site purulent drainage is not considered as a surgical site infection. The aggressiveness of the infection in this case resembles the course of an untreated descending necrotizing mediastinitis arising from odontogenic or cervico-facial infection. Another similarity is the dissemination of the infection from pleural space to the pericardial space through the opening of the right pleura. Infection in the setting of descending mediastinitis may spread across fascial planes, thus cross-contaminating into the anterior, middle, and posterior mediastinum and even pleural spaces. As outlined in this case, mediastinitis remains a rare but devastating complication of open heart surgery. While prompt diagnosis and emergent surgical intervention are crucial for better outcome, the presenting symptoms can be easily confused with more common problems such as cardiac tamponade. Therefore, a high index of suspicion for mediastinitis is crucial for survival even in the absence of surgical site infection. Conflict of interest: none declared.