When the aorta ruptures spontaneously, rather than as the result of trauma, it is usually in an aortic aneurysm. Rupture of an aortic aneurysm should not be confused with aortic dissection.

The aorta is such a large blood vessel that, if it ruptures, death is very rapid although the process might be slow enough to permit emergency surgery. However, time is of the essence. The ideal management is to repair the aneurysm before rupture occurs. Often there is no knowledge of the presence of an aneurysm and the first sign is rupture, rapid exsanguination and death.¹

Epidemiology

About 6,000 men a year die from ruptured aortic aneurysm in England and Wales, accounting for about 2% of deaths in men.² Women are much less frequently affected.

Risk factors

The presence of an aneurysm is a risk for rupture. The larger the lesion, the more likely it is to bleed. Smoking and hypertension are additional risks.

Presentation

Thoracic aortic aneurysm (TAA)

• It will cause chest pain that may be indistinguishable from acute myocardial infarction (MI) in terms of nature and distribution.
• Haemoptysis can occur.
• If bleeding occurs into the mediastinum it can cause cardiac tamponade and rapidly be fatal. The patient will probably never reach hospital alive and the diagnosis is made post mortem.

Abdominal aortic aneurysm (AAA)

• Ruptured AAA presents with a classical triad of pain in the flank or back, hypotension and a pulsatile abdominal mass; however, only about half have the full triad.
• The patient will complain of the pain and may feel cold, sweaty and faint on standing.
• The following symptoms are listed with approximate frequency of presentation:
  • Abdominal pain (60%)
  • Back pain (70%)
  • Syncope (30%)
  • Vomiting (20%)

Examination

• A patient with a ruptured aneurysm at any level is likely to look pale and unwell and to be cold and sweaty.
• The pulse will be rapid, weak and thready. Hypotension is common.
• With a ruptured AAA there may well be a pulsatile mass in the vicinity of the bifurcation of the aorta. This is a few centimetres above the umbilicus and a little to the left.
• It may be tender and a bruit may be audible. Bleeding causes peritoneal irritation and it may appear as an acute abdomen.
• The following findings are listed with approximate frequency:
  • Palpable mass (90%)
  • Tenderness (80%)
  • Systolic blood pressure (BP) below 80 mmHg (40%)

Differential diagnosis

• The differential diagnosis for a ruptured TAA is that of chest pain, especially MI with cardiogenic shock but also massive pulmonary embolism.
• The differential diagnosis for ruptured AAA involves other causes of abdominal pain, including acute abdomen.

Investigations

If an aneurysm is ruptured investigations need to be swift and pertinent.

Laboratory studies

• Full blood count:
  NB: if there has not been time for haemodilution then haemoglobin will be normal. Anaemia is present in less than half of patients. Around 80% have a white cell count of 10x10⁹/l or more.
• Group and rapid cross-match whilst arranging surgery.
• Baseline biochemistry of urea and electrolytes should be performed.

Radiology

• Chest X-ray:
  For a TAA the chest X-ray may well show an enlarged base of aorta.
• Plain abdominal X-ray:
  For an AAA this will show the lesion in about 75%, as it is often calcified.
• Portable ultrasound:
  This examination may be helpful but there is not time for detailed assessment. If there is strong suspicion of a ruptured aneurysm then immediate surgery may be the investigation of choice.
• Other investigations:
  CT scan, MRI and angiography are occasionally useful in stable patients, but most patients require life-saving emergency surgery before these investigations can be carried out.

Electrocardiogram

• In patients presenting with chest pain, electrocardiogram (ECG) is important.

Management

This is a surgical emergency.

• Get large bore intravenous access as soon as possible and preferably before hospital.^1,2
• Group and cross-match. Large supplies of blood and blood products, including platelets and fresh-frozen plasma should be readily available.
• Arrange theatre immediately.
• The aim of surgery in an unstable patient is to secure surgical proximal aortic control without disturbing any tamponade effect provided by extra-aortic structures or haematoma.
• Resuscitation of hypovolaemic shock may require surgery to stem the bleeding rather than satisfactory resuscitation before induction of anaesthesia. Therefore an experienced anaesthetist is essential.
• The leaking or ruptured piece of aorta is replaced by a prosthetic graft. Techniques previously used in elective surgery for pre-ruptured aneurysms, such as stent graft therapy, are now being used in patients with ruptured aneurysms, with encouraging results.⁴

Complications

This is dramatic surgery, often in the old and frail.¹ Complications include:

• Acute renal failure
• Multi-organ failure
• Respiratory problems including failure and pneumonia

Prognosis

No more than 1 in 3 patients with a ruptured aortic aneurysm will reach hospital alive and, 20% of those who do, fail to reach theatre.¹Delay in diagnosis is a major risk factor.
Elective repair of AAA has a mortality of around 5% compared with 60% for emergency repair.⁵

The following factors are associated with a mortality rate in excess of 80%:

• Age over 80
• Presentation in shock with free intra-peritoneal rupture
• Failure of BP to rise, despite attempts at resuscitation
• Haematocrit below 25% on admission
• Pre-operative cardiac arrest

Document references

1. Tan WA; Abdominal aortic aneurysm, rupture. eMedicine, March 2007.
2. Earnshaw JJ, Shaw E, Whyman MR, et al; Screening for abdominal aortic aneurysms in men. BMJ. 2004 May 8;328(7448):1122-4.
3. Nelson, B Benzer T; Aneurysm, Thoracic. eMedicine. November 2008.
4. Mehta M, Taggert J, Darling RC 3rd, et al; Establishing a protocol for endovascular treatment of ruptured abdominal aortic aneurysms: outcomes of a prospective analysis. J Vasc Surg. 2006 Jul;44(1):1-8; discussion 8. [abstract]
5. Basnyat PS, Biffin AH, Moseley LG, et al; Mortality from ruptured abdominal aortic aneurysm in Wales. Br J Surg. 1999 Jun;86(6):765-70. [abstract]

Acknowledgements