Coronary Artery Pseudoaneurysm

Coronary artery pseudoaneurysm is a contained rupture of a coronary artery or graft. The sac is formed by thrombus, adventitia or pericardium and has no true vessel wall. It communicates with the lumen through a neck, so it can enlarge and rupture.

It is rare. Most cases follow percutaneous coronary intervention, particularly with perforation, atherectomy, oversized balloons or stents, or cutting balloons. Others follow coronary bypass surgery (at a graft anastomosis), trauma, or infection.

Infected pseudoaneurysm after stent implantation usually develops within 2 to 4 weeks. Organisms include Staphylococcus aureus and Pseudomonas aeruginosa, with Candida species less often. Corticosteroids, diabetes and repeated arterial access increase risk.

Natural history is unpredictable. Rupture produces tamponade or haemothorax, and thrombus within the sac can embolise or occlude the artery.

Pathophysiology.

Wall injury allows blood to escape the lumen. Surrounding tissue and clot contain it and form a sac that is continuous with the lumen. The sac expands under arterial pressure.

In infected cases, bacteria destroy the wall and the stent struts, which prevents healing. In graft anastomoses, suture line dehiscence from infection or tension produces a pseudoaneurysm at the proximal or distal anastomosis.

A true aneurysm contains all three layers and has a wide neck, so the two are distinguished by imaging and history.

Many patients have no symptoms, and the finding is incidental on follow up imaging. Others present with chest pain, an acute coronary syndrome, fever and sepsis, pericardial effusion with tamponade, haemothorax, a mediastinal mass, a continuous murmur or heart failure. After surgery, sternal wound infection or bleeding may be present.

• Coronary angiography: a contrast filled sac outside the expected vessel contour, with a narrow neck and delayed washout. Intravascular ultrasound or optical coherence tomography shows stent malapposition or a wall defect.
• CT coronary angiography or cardiac MRI shows sac size, thrombus, rim enhancement, relation to the sternum, pericardium and adjacent structures. Fluorodeoxyglucose PET-CT supports infection.
• Echocardiography for effusion, tamponade and regional wall motion. Chest radiograph for mediastinal widening.
• Infection workup: blood cultures (three sets before antibiotics), C-reactive protein, white cell count, and cultures of any wound or aspirated fluid.
• Perforation grading by contrast: crater without extravasation, myocardial or pericardial blush, extravasation with a jet of 1 mm or more, and cavity spilling.

Differential diagnosis.

• True aneurysm and ectasia.
• Coronary fistula and loculated pericardial effusion.
• Graft aneurysm of other cause, and mediastinal haematoma.
• Mycotic aneurysm from endocarditis.

Acute perforation with active leak (emergency).

• Occlude the leak with a prolonged balloon inflation at low to moderate pressure (10 to 15 minutes, with a perfusion balloon when available). Reverse heparin with protamine 1 mg for each 100 units given in the previous 2 to 3 hours (maximum 50 mg, slowly) when bleeding persists.
• Covered stent for a leak at a proximal or mid vessel segment. Coil or gelfoam embolisation for distal vessel leaks.
• Pericardiocentesis for tamponade, with a pigtail catheter left in place, and return of drained blood intravenously when needed. Emergency surgery for failed percutaneous control.
• Platelet transfusion is not routinely needed. Hold glycoprotein IIb/IIIa inhibitors.

Non-infected, stable pseudoaneurysm.

• Small (under 10 mm), asymptomatic and not enlarging: observe with CT angiography at 1, 3, 6 and 12 months. Continue single antiplatelet therapy, and avoid unnecessary anticoagulation.
• Symptomatic, enlarging, over 10 mm, thrombus filled or leaking: covered stent exclusion or coil embolisation by an experienced operator, or surgical resection or ligation with bypass grafting.
• Covered stent: aspirin 75 to 100 mg daily with ticagrelor 90 mg twice daily (or clopidogrel 75 mg daily) for 6 to 12 months because of the stent thrombosis risk. Pantoprazole 40 mg daily.

Infected pseudoaneurysm.

• Draw cultures, then start vancomycin 25 mg/kg intravenously as a loading dose, then 15 to 20 mg/kg every 8 to 12 hours (trough 15 to 20 mg/L), with piperacillin and tazobactam 4.5 g intravenously every 6 hours. Adjust to culture results and renal function.
• If Candida is isolated: liposomal amphotericin B 3 to 5 mg/kg intravenously daily, with step down to fluconazole 400 to 800 mg daily by susceptibility.
• Antibiotic duration is at least 6 weeks after source control.
• Surgical resection of the infected segment and stent, with bypass grafting using autologous conduit, is the definitive treatment. Percutaneous covered stents are not used in infected pseudoaneurysm except as a bridge.

Graft anastomotic pseudoaneurysm. Re-operation with revision of the anastomosis. Transcatheter coil embolisation or covered stent in selected patients who are poor surgical candidates.

Monitoring. Haemodynamics and ECG for 24 to 48 hours after any leak, echocardiography at 24 hours, 1 week and 1 month, inflammatory markers weekly during antibiotics, imaging of the aneurysm at 1 week, 1 month and 3 months.

Referral and escalation. Refer every pseudoaneurysm to a centre with interventional and surgical capacity. Same hour escalation for tamponade, sepsis, enlarging sac, or new myocardial ischaemia.

Special groups.

• Pregnancy: rare; treat urgent leaks with the same techniques while limiting fluoroscopy; avoid fluconazole in the first trimester.
• Kidney impairment: adjust vancomycin by levels, avoid prolonged piperacillin and tazobactam with vancomycin when possible because of nephrotoxicity, and limit contrast.
• Immunosuppressed patients: lower threshold for fungal cover and surgery.