Aortic Pseudoaneurysm

An aortic pseudoaneurysm (false aneurysm) is a contained rupture of the aortic wall. All three layers are breached, and blood is held by adventitia, periaortic tissue or clot.

It has a high risk of rupture and is treated on diagnosis. The neck is usually narrower than the sac.

Causes are blunt trauma (at the isthmus beside the ligamentum arteriosum), cardiac surgery (aortotomy, cannulation sites, suture lines, anastomoses, aortic valve and root surgery), endovascular procedures, endocarditis with root abscess, penetrating atherosclerotic ulcer, aortic dissection, aortitis and Behçet disease.

After cardiac surgery it develops in under 1% of operations, and more often after redo sternotomy and surgery for endocarditis. It appears months to years later.

Pathophysiology. A breach in the wall allows blood to escape into a cavity limited by surrounding tissue. Infection, suture dehiscence and sustained pressure expand the cavity. The sac may erode into the sternum, airway, oesophagus or heart chambers.

• Often asymptomatic and found on imaging after surgery or trauma.
• Chest or back pain, dyspnoea, cough, hoarseness, dysphagia and superior vena cava syndrome from compression.
• Fever, sternal wound sinus or discharge, and sepsis with infection.
• Haemoptysis or haematemesis (fistula), continuous murmur (fistula to a cardiac chamber), embolism, heart failure.
• Massive bleeding at redo sternotomy if the sac lies behind the sternum.

Red flags.

• Haemoptysis, haematemesis, sudden pain or hypotension
• Fever, positive blood cultures or raised inflammatory markers
• Sac lying close to the posterior sternum before redo surgery
• Enlargement on serial imaging, or a neck under 5 mm with a large sac
• New murmur, or chest wound drainage after cardiac surgery

• CT angiography. Saccular outpouching with a narrow neck, discontinuity of the wall, periaortic haematoma, air or fluid (infection), and relation to the sternum before reoperation.
• Transoesophageal echocardiography for root abscess, valve disease and fistula. MR angiography when radiation or contrast is a concern.
• Infection workup. Blood cultures (3 sets), ESR, CRP, white cell count, procalcitonin, and FDG PET-CT. Culture and 16S rRNA PCR of tissue at surgery.
• Trauma grading. Grade I intimal tear, II intramural haematoma, III pseudoaneurysm, IV rupture.
• Other. Syphilis serology, tuberculosis tests, ANCA and Behçet features in unexplained cases.

Differential diagnosis.

• True aortic aneurysm (wide neck, all layers intact)
• Penetrating atherosclerotic ulcer
• Aortic dissection with aneurysmal false lumen
• Ductus diverticulum (smooth, obtuse margins with no wall disruption)
• Kommerell diverticulum
• Periaortic abscess and mediastinal haematoma
• Mediastinal mass and mycotic aneurysm

Repair is indicated at diagnosis, because rupture risk is high. Delay is acceptable only when the neck is tiny, the patient is stable and surgical risk is prohibitive, with close imaging.

Impulse control while awaiting repair. Esmolol 500 microgram/kg intravenously over 1 minute, then infusion 50 microgram/kg/min, repeating the bolus and increasing the infusion by 50 microgram/kg/min every 4 to 5 minutes, maximum 200 microgram/kg/min, to a heart rate near 60/min and systolic pressure of 100 to 120 mm Hg. Morphine 2.5 to 5 mg intravenously, titrated, for pain. Crossmatch blood.

Surgical repair.

• Redo sternotomy carries a risk of sac rupture. Establish cardiopulmonary bypass first through femoral or axillary cannulation and cool before re-entry.
• Patch or direct repair for a small neck, graft replacement for a large defect, and debridement with in situ reconstruction (graft or homograft) when infected.
• Transcatheter closure with a vascular plug or coil, or a covered stent, is used for a narrow neck or high surgical risk in selected patients.
• Thoracic endovascular repair for isthmus and descending pseudoaneurysm. Traumatic injuries of grade III or IV are repaired within 24 hours when the patient is stable, and sooner if unstable. Minor injuries (grade I, small grade II) are managed with beta blockade and surveillance imaging.
• Complications: stroke, spinal cord injury, endoleak, graft infection and recurrence.

Infected pseudoaneurysm.

• Empirical antibiotics after blood cultures: vancomycin 25 to 30 mg/kg intravenously as a loading dose (maximum 3 g), then 15 to 20 mg/kg every 8 to 12 hours (usual maximum 2 g for each dose), adjusted to a trough of 15 to 20 mg/L or an AUC of 400 to 600 mg·h/L, lengthening the interval and using levels in renal impairment. Plus piperacillin-tazobactam 4.5 g intravenously every 6 hours (4.5 g every 8 hours at creatinine clearance 20 to 40 mL/min, every 12 hours under 20 mL/min), or meropenem 1 g every 8 hours (1 g every 12 hours at creatinine clearance 26 to 50 mL/min, 500 mg every 12 hours at 10 to 25 mL/min, 500 mg every 24 hours under 10 mL/min).
• Directed therapy by culture: flucloxacillin 2 g every 4 hours (maximum 12 g daily) or cefazolin 2 g every 8 hours for methicillin susceptible staphylococci, ceftriaxone 2 g every 24 hours for susceptible streptococci and Salmonella.
• Duration: at least 6 weeks intravenously after debridement, with oral suppression chosen by susceptibility for months to lifelong when an endograft or prosthetic material remains.
• Source control: treat endocarditis, osteomyelitis or other sources.

After repair. Aspirin 75 to 100 mg orally once daily after an endograft or patch. Anticoagulation only with another indication. Blood pressure under 130/80 mm Hg.

Special groups. Renal impairment: adjust antibiotics and use levels. Region: tuberculosis and syphilis cause pseudoaneurysm in sub-Saharan Africa, so test for both.

Monitoring. CT angiography at 1 month, 6 months and 12 months, then yearly. CRP and white count weekly during antibiotics. Vancomycin levels and creatinine twice weekly. PET-CT when infection is suspected.

Referral and escalation. Refer urgently to a cardiothoracic or vascular centre with an aortic team and infectious diseases. Emergency for rupture, bleeding, sepsis or enlargement.