Authors:
Jared Cappelli, MD¹
Amber Edwards, MD²
¹University of Tennessee Medical College - Nashville, General Surgery
Residency, Nashville, TN
²Ascension Saint Thomas Hospital West, Department of Surgery, Nashville,
TN
Key Words: Epicarditis, Endocarditis, Epicardial Abscess, MRSA, Atrial
Vegetation, Redo Sternotomy, Mediastinitis, Pericarditis, coronary
artery bypass grafting
Abstract :
Endocarditis originating from a prior venous cannulation site is
undescribed in the current literature. Infections of the heart pose
significant morbidity and mortality to patients, therefore prompt
recognition, diagnosis, and treatment are critical. Our patient
underwent coronary artery bypass grafting (CABG) and developed a
postoperative sternal wound infection with methicillin resistant
staphylococcus aureus (MRSA). After failing nonoperative management,
redo-sternotomy was performed with atrial wall debridement and patch
repair. During this procedure, two unexpected small discrete abscess
pockets of the right atrial epicardium were discovered. One of the
abscess pockets fistulized into the right atrium and was noted to be at
his prior venous cannulation site for cardiopulmonary bypass as
evidenced by neighboring prolene suture. The patient had an uneventful
recovery and was discharged home on postoperative day 7. Transthoracic
echo was obtained 6 weeks after his second operation and did not show
any recurrence of endocarditis. We present a unique case of persistent
cardiac infection with a complicated course and management strategy.
Introduction :
Post-CABG mediastinal infections significantly increase hospital length
of stay, cost, and patient mortality (3). The overall incidence of deep
sternal wound infections (DSWI) following median sternotomy is reported
to be between 0.2% and 3% (4). Some researchers have found DSWIs to be
associated with an almost tripled health care cost and doubled hospital
length of stay, reinforcing our current understanding of the significant
economic impact (8).
There are currently no described cases of endocarditis of a previous
cannulation site for cardiopulmonary bypass. We describe a case in which
a patient developed a MRSA sternal wound infection after coronary bypass
that was complicated by persistent bacteremia and right atrial
vegetation ultimately requiring redo sternotomy with intraoperative
discovery of two epicardial abscess pockets eroding through the atrial
wall. One of the abscess pockets communicated directly with the right
atrium and was noted to be at the prior venous cannulation site for
cardiopulmonary bypass as evidenced by neighboring prolene suture. Our
goal is to bring awareness to a previously undescribed cardiac infection
to assist other clinicians in promptly diagnosing and treating this
complicated disease process.
Case Report :
History:
The patient is a 56-year-old male with a history of hypertension,
hyperlipidemia, atrial fibrillation, and coronary artery disease status
post four vessel CABG. His initial postoperative course was complicated
by a delayed MRSA positive sternal wound infection requiring debridement
and bilateral pectoralis major flaps three months after his index
operation. At that time he was also found to have MRSA bacteremia. He
was discharged on a prolonged course of intravenous antibiotics with
clearing of his blood cultures. Unfortunately, he developed recurrent
fevers, and repeat blood cultures and a transthoracic echocardiogram
were obtained. Blood cultures again were positive for MRSA positivity
and echo showed right atrial/tricuspid valve vegetation concerning for
MRSA endocarditis. The patient was readmitted and restarted on broad
spectrum IV antibiotics. A transesophageal echocardiogram was obtained
that confirmed a large multi lobular mobile vegetation on the anterior
portion of the right atrial free wall and extending into the right
atrial appendage, measuring 3.0 cm x 1.7 cm. His ejection fraction at
that time was 52%. He underwent catheter aspiration of the right atrial
vegetation with the Angiovac™system with an estimated 80% extraction
during that procedure. He was able to clear his blood cultures and was
discharged home with IV antibiotics and plan for 1 month follow up blood
cultures and echocardiogram. Unfortunately, his follow up blood cultures
were once again positive and his echo redemonstrated a mobile right
vegetation. He was subsequently readmitted and started on vancomycin.
Confirmatory transesophageal echo was performed that showed a large 3.1
cm x 1.4 cm mobile mass in the right atrium. At this point, it was
decided the patient would require operative intervention to clear his
infection and atrial vegetation. He underwent a preoperative left heart
catheterization which demonstrated widely patent bypass grafts.
The patient was taken to the operating room and underwent reoperative
sternotomy. There were significant scarring/adhesions of the
pericardium and epicardial tissues. Prior bypass grafts were noted and
avoided. Arterial access for cardiopulmonary bypass was the ascending
aorta and venous access were the superior vena cava and inferior vena
cava. The inferior vena cava was accessed percutaneously through the
right common femoral vein. During the dissection two small pockets of
epicardial abscess were identified and cultured. The right atrium was
opened and the vegetation identified and removed. It seemed to be at the
area of the prior venous cannulation site and near the two small
epicardial abscesses with one of the abscess pockets communicating
directly with the right atrium. All involved areas of the right atrium
were removed. The tricuspid valve was evaluated and did not appear
infected or to have structural defects. The right atrial defect was too
large to close primarily, and a bovine pericardium patch reconstruction
was used. Final cultures from the operation were positive for MRSA.
The patient’s postoperative course was uneventful and he was discharged
home on postoperative day 7 with 6 weeks of IV antibiotics. He had
repeat blood cultures and a transthoracic echocardiogram four weeks
after discharge which were all negative for recurrent infection.
Discussion :
While relatively rare, the U.S. sees between 40,000 and 50,000 new
endocarditis cases per year (10). The evolving risk factors of this well
described infection have been characterized in generations of cardiac
literature. Prosthetic valve replacement, immunosuppression, and IV drug
abuse are the principal risk factors (11). Despite advances in medicine,
endocarditis is still associated with a 15-20% in-hospital mortality
(9). Endocarditis after CABG is a known risk factor for the development
of a DSWI, but the development of endocarditis following DSWI for
non-valvular surgery is rare (13). We have presented a unique case of
persistent cardiac infection with a complicated course and management
strategy. There are currently no documented cases of epicardial abscess
originating from a prior cannulation site. It is important for
clinicians to be aware of this disease process and the risk it poses to
patients with recurrent mediastinal infections after cardiopulmonary
bypass. We suspect the non-absorbable suture used to close this
cannulation site in the standard fashion may have acted as a nidus for
recurrent infection in a patient whose postoperative course was
complicated by MRSA mediastinitis. This may have allowed bacteria to
erode through the atrial wall posing significant risk of hemorrhage. An
awareness of this disease process may lean the clinician towards earlier
reoperation and potentially prevent catastrophic hemorrhage.
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