Keywords
CABG - aortic pseudoaneurysm - aneurysm - cardiopulmonary bypass
Introduction
Surgical revascularization is performed for patients with significant left main coronary
artery disease. The risks associated with coronary artery bypass graft (CABG) surgery
are well known with late dissection of the aorta and aortic pseudoaneurysm formation
cited separately in various case reports and retrospective reviews; however, there
is a paucity of literature on the concurrent presentation of both conditions.[1]
[2]
[3] This case report highlights the preoperative workup, surgical approach, and postoperative
management of a patient with both an aortic pseudoaneurysm and dissection 2 years
after the index CABG.
Case Report
A 65-year-old male with a history of allergic bronchopulmonary aspergillosis (ABPA)
and CABG (left internal mammary artery [LIMA] - left anterior descending artery [LAD],
saphenous vein graft [SVG] – obtuse marginal [OM], saphenous vein graft [SVG] – right
posterior descending artery [RPDA]) 2 years prior originally presented to an outside
hospital with worsening shortness of breath and was found to have a large mid-ascending
aortic pseudoaneurysm measuring 78 × 53 × 92mm ([Fig. 1]). The patient was transferred to our medical center for higher level of care and
further workup in the setting of his known history of ABPA. The right coronary artery
territory vein graft originated from the pseudoaneurysm sac, whereas the left circumflex
artery territory vein graft, native right coronary artery, and native left coronary
artery originated from the ascending aorta. Imaging did not reveal periaortic hematoma
or active contrast extravasation in the mediastinum or pericardium. Coronary angiography
showed patent LIMA-LAD graft with diffuse disease. The SVG to the RPDA was diffusely
ectatic and the SVG to the OM had mild luminal irregularities. A preoperative echo
demonstrated preserved biventricular function without valvular disease. Infectious
disease was consulted preoperatively due to the history of ABPA and did not find any
contraindications to proceed with surgery as his ABPA was reported to be well controlled
and he was not currently taking any medications for his diagnosis. It should be noted
that this diagnosis was made at an outside hospital without histopathological evidence
available to corroborate the diagnosis.
Fig. 1 Preoperative computed tomography with three-dimensional reconstruction demonstrating
large pseudoaneurysm at mid-ascending aorta.
Operative notes from the index operation 2 years prior were obtained and were documented
a standard median sternotomy approach to expose the heart without any significant
ascending aortic atheroma visualized on epiaortic ultrasound, which would prevent
safe cannulation or cross-clamping. Thus, the aorta was cannulated through a double
purse string suture, an antegrade cardioplegic cannula was introduced into the ascending
aorta, and an aortic cross-clamp was placed in the standard fashion.
With the above findings and details from the prior operation, the decision was made
to go to the operating room for surgical repair of the large pseudoaneurysm. Peripheral
access for cardiopulmonary bypass was established through the right groin and axilla.
Upon entering the chest, the large 7 cm ascending aorta pseudoaneurysm with a 2 cm
connection to the proximal ascending aorta was discovered, as well as a focal ascending
aortic dissection flap at the proximal SVG-OM anastomosis site. The SVGs were liberated
as coronary buttons and the pseudoaneurysm was resected and replaced with a 32 mm
Hemashield graft ([Fig. 2]). The venous bypass graft coronary buttons were reimplanted onto the neo-aorta.
Intraoperative transesophageal echocardiogram was notable for left ventricular ejection
fraction (LVEF) 65% without left ventricular dysfunction or wall motion abnormalities.
Cardiopulmonary bypass and cross-clamp time were 328 and 178 minutes, respectively.
The patient was transferred to the Cardiothoracic Intensive Care Unit (CTICU) in critical
but stable condition and had an uneventful recovery.
Fig. 2 Pseudoaneurysm with 2 cm connection to proximal ascending aorta.
Discussion
Ascending aortic dissection after CABG is a rare complication with less than 0.2%
incidence.[1] The retrospective study by Eitz et al showed the majority of dissections occurred
at the proximal anastomosis (41.7%), supporting the hypothesis that these types of
dissections are caused by surgical trauma through manipulation of the aorta.[1] Arterial cannulation, aortic cross clamping, and graft anastomoses can weaken the
aorta and disrupt the intima, causing dissections or pseudoaneurysms, as well as inadequate
full-thickness bites when performing anastomoses.[2] This includes whether the operation is performed on pump or off pump with various
stabilization devices to perform the anastomosis or partial aortic clamping. The initial
weakening of the aorta during the operation, in addition to the common comorbidities
associated with patients with coronary artery disease, such as hypertension and atherosclerosis,
has been hypothesized to contribute to the late development of aortic dissection after
CABG.[2]
The dissections can occur intraoperatively or as far out as 10 years after the index
operation; however, late dissections are extremely rare and mainly found in case reports.[1]
[2] A small retrospective review by Dhadwal et al found the mortality associated with
the development of a pseudoaneurysm arising from the ascending aorta after prior cardiac
surgery was as high as 60% and the average time to pseudoaneurysm repair from index
operation was 5 years.[3] Although this was a 10-year retrospective review study, it was underpowered with
five total patients contributing to data.[3] A higher powered, more contemporary, study by Lou et al looked at mortality in 365
patients who underwent reoperative aortic arch intervention after previous cardiac
surgery and found a 30-day mortality of 13.4%, and long-term follow-up mortality as
high as 38%.[4]
Infections also contribute to the formation of pseudoaneurysms as Osler first coined
the term mycotic aneurysm in 1885 to describe a pseudoaneurysm with an infectious
etiology.[2]
[3]
[5]
Aspergillus is a type of fungus that has been found in ascending aortic pseudoaneurysms in patients
after prior cardiac surgery.[6] However, despite our patient's history of ABPA, he was not currently infected with
aspergillosis at the time of his redo operation based on his lab tests showing a negative
Aspergillus galactomannan antigen. It remains unclear whether he had an active infection after his index operation
and whether that precipitated the formation of the pseudoaneurysm.
Conclusions
The development of an aortic pseudoaneurysm in combination with an ascending aortic
dissection after prior CABG is rare and should be managed with prompt surgical intervention
to prevent the potentially catastrophic consequences of pseudoaneurysm rupture. Providers
should also be vigilant for other causes of aneurysms, such as infections, in order
to adequately manage concomitant disease processes.
