Ruptured Thoracic Aortic Aneurysm

Ruptured thoracic aortic aneurysm is rupture of a dilated ascending, arch or descending thoracic aorta (aneurysm diameter 4.5 cm or more in the descending aorta) with bleeding into the mediastinum, pleura or pericardium. Mortality is very high, and most patients die before surgery.

Epidemiology. Thoracic aneurysm occurs in about 6 to 10 people in 100,000 each year. Rupture risk rises sharply over a diameter of 6 cm for the descending aorta and 5.5 to 6 cm for the ascending aorta.

Causes and associations. Atherosclerosis and hypertension, degenerative medial disease, connective tissue disorders (Marfan, Loeys-Dietz, vascular Ehlers-Danlos), bicuspid aortic valve, aortitis (giant cell arteritis, Takayasu, syphilis), infection (mycotic aneurysm), chronic dissection and trauma.

Pathophysiology. Wall stress increases with diameter and pressure and exceeds wall strength, causing rupture into the left pleural space (most often, with haemothorax), mediastinum, pericardium (tamponade), oesophagus (aortooesophageal fistula) or bronchus (haemoptysis).

Presentation is sudden severe chest or back pain, shock, dyspnoea, haemoptysis, haematemesis (fistula), hoarseness, dysphagia or stridor from compression, and syncope. Dullness at the left base suggests haemothorax. Chiari triad (chest pain, sentinel haematemesis, then massive bleeding after a symptom free interval) indicates aortooesophageal fistula.

Red flags.

• Known aneurysm with new pain, or pain with shock.
• Haematemesis or haemoptysis with a thoracic aneurysm.
• Widened mediastinum or left pleural opacity on chest radiograph.

In unstable patients, bedside ultrasound (pericardial and pleural blood) and transoesophageal echocardiography, and go to theatre. In stable patients, CT angiography of the aorta (extent, contrast leak, branch vessels, haemothorax). Send group and crossmatch, coagulation, full blood count, creatinine, lactate and ECG. Do not perform endoscopy blindly when fistula is suspected.

Differential diagnosis. Acute aortic dissection, acute coronary syndrome, pulmonary embolism, oesophageal rupture and tension pneumothorax.

Resuscitation. Permissive hypotension (systolic pressure 80 to 90 mmHg) unless malperfusion or tamponade is present, large bore access, balanced blood products (1 red cell unit to 1 plasma to 1 platelet pool), calcium, warmth and analgesia (fentanyl 25 microgram IV). Limit crystalloid. Control heart rate and pressure if hypertensive and bleeding is contained (esmolol 500 microgram/kg IV then 50 to 300 microgram/kg/min, target systolic pressure 100 to 120 mmHg).

Airway. Intubate in theatre. Selective lung ventilation with a double lumen tube or bronchial blocker helps in left thoracotomy or fistula.

Repair.

• Thoracic endovascular repair for descending aorta with suitable anatomy, which is the first choice because of lower early mortality.
• Open repair (left thoracotomy with clamp, bypass or circulatory arrest) for ascending and arch ruptures and unsuitable descending anatomy.
• Combined endovascular and open procedures for aortooesophageal fistula, with oesophageal repair or diversion and prolonged antibiotics.

Spinal cord protection. Maintain mean arterial pressure over 80 to 90 mmHg after repair, avoid anaemia and hypotension, and use cerebrospinal fluid drainage (keep pressure under 10 to 15 mmHg) when extensive aorta is covered or neurological deficits appear. Neurological checks hourly.

Antibiotic. Cefazolin 2 g IV at induction, and broad cover (for example piperacillin-tazobactam 4.5 g IV every 6 hours plus vancomycin) for mycotic aneurysm or fistula, for at least 6 weeks.

Heparin. 5000 units IV before clamping or stent insertion, when time allows.

Monitoring. Arterial pressure, lactate, urine output, neurological function of the legs, haemoglobin and coagulation.

Referral and escalation. Cardiothoracic or vascular surgery, anaesthesia, interventional radiology, and blood bank at once. Transfer to an aortic centre only if stable.

Special groups. In connective tissue disease, use open repair when feasible. In pregnancy, plan with obstetrics and cardiac surgery.