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.