Keywords
infectious endocarditis - composite aortic graft - combined surgery - mediastinal
collection
Introduction
Infective endocarditis (IE) is an important cause of cardiovascular pathology that,
despite diagnostic and therapeutic advances, continues to be a serious disease that
leads to a high morbidity and mortality.[1] The presence of local complications (such as periannular tissue destruction or abscess)
increases the complexity and mortality associated with IE surgery.[2] An episode of IE affecting a composite graft after aortic root replacement can be
a life-threatening complication.[3]
[4] Moreover, redo procedures after a previous coronary artery bypass grafting (CABG)
surgery, with a patent internal mammary artery (IMA), may significantly increase the
risk of the surgical procedure.
We report the case of a 70-year-old man with an episode of IE affecting a composite
aortic root and mitral prosthesis, who had an extremely high surgical risk, in whom
a previous saphenous vein graft was found to be detached from the aortic graft because
of endocarditic involvement, forming a huge collection of blood in the anterior mediastinum.
Case Presentation
A 70-year-old man was emergently referred to the Cardiac Surgery Department due to
a confirmed diagnosis of acute IE. The patient had a previous clinical history of
arterial hypertension and atrial fibrillation. He had two previous cardiac surgery
procedures. He underwent, 10 years ago, a full aortic root replacement with a composite
graft (Dacron graft with mechanical valve, Bentall-De Bono procedure) associated with
triple coronary bypass (IMA to anterior descending artery and vein grafts to intermediate
branch and posterior descending artery).
The second procedure was performed 6 months before the current episode, when the patient
suffered from a native mitral valve IE episode (Staphylococcus epidermidis). He was admitted in cardiogenic shock with confirmed endocarditic involvement of
the mitral valve. The critical preoperative status did not permit a preoperative angiogram.
No signs of myocardial ischemia were present, so the patient underwent an emergent
mitral valve replacement by a mechanical prosthesis performed through a right thoracotomy
approach, to avoid possible complications related to the previous coronary grafts.
The postoperative course was uneventful, and the patient was discharged home after
completing 6 weeks of intravenous antibiotic treatment with daptomycin and rifampicin.
The current episode started when the patient was readmitted to our institution in
a critical clinical state, with congestive heart failure and sepsis. The patient presented
with persistent fever, dyspnea, orthopnea, and paroxysmal nocturnal dyspnea. On physical
examination, no peripheral stigmata of endocarditis were found. A diastolic murmur
was heard along the left sternal border. Three blood cultures were positive for Staphylococcus aureus. Antibiotic treatment was initiated with intravenous oxacillin, rifampicin, and gentamicin.
Complete imaging studies were conducted.
Transesophageal echocardiography revealed a mitral peri-prosthetic leak that caused
severe mitral valve regurgitation. There were vegetations on both the aortic and mitral
prosthetic valves. Annular involvement was diagnosed, with the presence of a large
perivalvular aortic abscess ([Fig. 1]).
Fig. 1 Transesophageal echocardiography. (A) Prosthetic aortic valve with a perivalvular abscess. (B) Mitral periprosthetic leak. (C) Mitral valve 3D reconstruction. (D) Vegetations on the mitral prosthetic valve.
The coronary angiography showed atherosclerotic coronary disease of the anterior descending
and distal circumflex arteries. All the previous bypasses were not patent. It was
not possible to selectively make an injection in the previous vein grafts. Comparison
with the previous angiogram was impossible, as no coronary angiography was performed
for the previous mitral IE surgery due to the urgency of the intervention.
A preoperative thoracic computed tomographic (CT) scan was performed, which revealed
a huge collection of unknown origin in the anterior mediastinal space (100 × 55 × 75
mm), adjacent to the Dacron composite graft, in its anterior aspect, and in close
contact with the thoracic wall ([Fig. 2]). This was a clearly delimited collection, with dense and heterogeneous content.
As there were no images of flow of contrast inside this collection, it was suspected
to be purulent material. Soft tissue attenuation was described around the mechanical
aortic valve, suggestive of active IE. After a period of stabilization (13 days) and
antibiotic therapy, the patient underwent surgery.
Fig. 2 Computed tomography scan with intravenous contrast. Axial section showing a big collection
in the mediastinal space.
Before opening the sternum, because of the suspected high risk of rupture, arterial
cannulation was performed in the axillary artery and venous cannulation in the femoral
vein. Cardiopulmonary bypass and hypothermia were established. During the sternal
opening, a massive acute bleeding occurred. The bleeding was partially controlled
by occlusion of the bleeding point by digital pressure through the partially opened
sternum. After completing the sternal opening, the site of bleeding was identified.
It was caused by the complete detachment from the aorta of the previous vein graft
anastomosis, due to endocarditic involvement. The institution of cardiopulmonary bypass
before sternal opening allowed the medical team to maintain a stable hemodynamic situation,
and the bleeding site was controlled.
All the affected tissues were excised, including debridement of all infected and necrotic
regions. The patient underwent a mitral valve replacement and a full root replacement
with a mechanical composite graft (Medtronic Inc.). It was not possible to mobilize
the native coronary ostia because of the firm adhesions due to the previous surgeries
and the severe IE, so the new Bentall-De Bono procedure was performed with the Cabrol
modification,[5] with an 8-mm Dacron graft. As there was no critical ischemic heart disease in the
preoperative checkup, no new coronary bypasses were constructed. Despite the prolonged
aortic cross clamp time (206 minutes) and pump time (300 minutes), no temporary circulatory
support was necessary. The patient was transferred to the intensive care unit in a
stable hemodynamic situation, with low-dose inotropic drugs and good perfusion.
During the first 24 hours after the intervention, it was possible to reduce the dose
of inotropic support because of the stable hemodynamic state of the patient. Unfortunately,
on the second postoperative day, the patient had fever and worsening of infectious
parameters. The patient suffered from an episode of septic shock due to Klebsiella pneumoniae (Carbapenemases producer) that triggered multiorgan failure with acute renal failure,
coagulopathy due to low flow hepatic failure, intestinal ischemia, and respiratory
involvement. He died due to an acute multifactorial etiology shock refractory to medical
treatment.
Discussion
The presence of IE perivalvular complications increases the complexity associated
with IE surgery.[2] Periannular tissue destruction, abscess formation, prosthesis dehiscence, presence
of vegetation, and pseudoaneurysm formation are serious complications associated with
a high mortality rate.[4] In addition, composite graft IE after aortic root replacement can be a life-threating
complication,[3] and recurrent valve IE remains a surgical challenge because a more radical and aggressive
surgical treatment is required to prevent a recurrent infection.
We report a case with an extremely high surgical risk, which was a second episode
of IE, with an estimated 30-day mortality by EuroSCORE I and II of 81.6 and 42.6%,
respectively. The case was discussed in the multidisciplinary endocarditis team, with
the collaboration of the cardiologist, microbiologist, and cardiac surgeon, and despite
the extreme surgical risk, the decision to proceed with surgery was accepted, as it
was the only chance for survival. Surgery appeared to be the only possible strategy
based on the clinical management guides.[1]
[6]
Moreover, we found a very infrequent complication of IE: the total detachment of a
previous vein graft anastomosis ought to an endocarditic involvement of the ascending
aortic graft, with the formation of a large collection of blood contained by the adhesions
of the previous surgeries. Prosthesis detachment due to IE affection[7] and ischemia due to abscess compromise[8] have been described, but we found no literature describing bypass graft involvement
by infection.
Owing to the absence of similar reports in the previously published literature, we
consider that this case is a good example of an extreme IE affectation. Moreover,
our findings may help the planning of the surgical strategy in the unusual case of
a mediastinal collection in an IE patient affecting a previous full-root graft and
saphenous vein grafts. Cannulation for cardiopulmonary bypass before opening the sternum
allowed the surgical team to control the potentially fatal complication of massive
bleeding. Peripheral cannulation prior to sternal opening could be considered mandatory
in advanced IE cases, when the destruction of outer heart structures is suspected.
