Discussion
Pneumopericardium may occur due to multiple etiologies, which can be broadly classified as iatrogenic, inflammatory (pericarditis), fistulous (with adjacent air containing organs) and traumatic. Iatrogenic causes include pericardiocentesis, thoracocentesis, laparoscopy, cardiac electronic device implantation, sternal bone marrow aspiration and esophagoscopy. Pneumopericardium occurring after device implantation is rare, with literature limited to anecdotal case reports. The mechanisms to explain development of pneumopericardium after device implantation have been variously proposed on a case to case basis.2-8 Perforation of the helix of the right atrial lead into the right pleural cavity through the atrial wall and pericardium can cause pneumopericardium with right pneumothorax, especially with active fixation leads being implanted in thin, frail and elderly patients.2-5 This is the most common mechanism reported for pneumopericardium after CIED implantation.2-5 The association of pneumopericardium with left pneumothorax which occurs as a complication of subclavian venous puncture has been hypothesized to occur secondary to presence of a pleuro-pericardial connection. Chen et al reported partial absence of the left pericardium as the cause of such a pleuro-pericardial connection.6 It has been hypothesized that pleuro-pericardial micro-fistulae may form in patients who have undergone previous cardiac surgery.7-8 Thus in patients with previous history of cardiac surgery, these connections can then track air and consequently result in a pneumopericardium in case a pneumothorax occurs. In the present case, a connection between the left pleural cavity and the pericardium was created by the placement of the epicardial lead, as demonstrated conclusively by the CT scan. This is an important surgical consideration, as this situation may arise if adequate precautions are not observed to retract lung tissue during placement and tunneling of an epicardial lead.
Once a diagnosis of pneumopericardium is made, cardiac tamponade must be carefully excluded. Transthoracic echocardiography may be tricky due to an inadequate echo window, secondary to air inside the pericardium. The hemodynamics and clinical picture are helpful in this regard. An elevated jugular venous pressure with absent y descent, low cardiac output with hypotension, paradoxical pulse and distant heart sounds help in making a clinical diagnosis of cardiac tamponade, requiring immediate relief with pericardial drainage. If there are no signs of tamponade, drainage of the pneumothorax with an inter-costal drainage tube is all that required to treat both pneumopericardium and pneumothorax due to the presence of connection between the two cavities, as in this case.
To conclude, pneumopericardium is a rare complication occurring after CIED implantation. A CT scan helps delineating the mechanism of pneumopericardium. In a patient with previous epicardial lead implantation, the possibility of the lead creating a pleuro-pericardial connection should be considered. After ruling out cardiac tamponade, drainage of the pneumothorax is adequate to drain both air spaces.