Aneurysm

SUMMARY: Aortic Aneurysms greater than about 5 cm should be considered urgently for surgery to prevent rupture or dissection. Initial misdiagnosis of ruptured Abdominal and dissecting Thoracic Aortic Aneurysms is common, and for dissection such delays have a significant adverse effect on survival. Missing a sentinel bleed is a relatively common cause of viable medical malpractice litigation

An aneurysm is a dilatation (ballooning) of a blood-vessel, typically an artery or the aorta.

As the wall of the artery or aorta progressively balloons it weakens and is increasingly likely to rupture (leak or burst). A leak may do no serious harm but can produce warning symptoms which, if recognised, can result in intervention that prevents a catastrophic bleed.

Aneurysm can occur or form on many arteries but most commonly encountered in Personal Injury and Medical Malpractice litigation are aneurysms of the aorta and cerebral arteries.

Aortic Aneurysm

Aortic Aneurysm greater than about 5 cm should be considered urgently for surgery to prevent rupture or dissection. Just as inflating a balloon requires most air pressure initially, rate of enlargement of an aortic aneurysm accelerates with increasing size¹^,².

Progressive enlargement also increases the probability of aortic dissection. In this process, which is often quickly lethal, there is rupture of only the intima (inner coat) of the aorta, resulting in the formation in the aortic wall of a pseudo-aneurysm or false passage that the high-pressure blood causes to propagate rapidly.

Although small aortic aneurysms do have a significant tendency to rupture, probability of rupture increases with increasing size^1,³.

For both abdominal¹ and thoracic aortic aneurysm³, 4-5 cm is generally the critical diameter requiring urgent consideration of surgical repair.

Practice Point

The larger an aortic aneurysms, the greater the

rate of annual enlargement
probability of dissection
probability of rupture

Dissection is misdiagnosed more commonly that rupture, perhaps because the wide range of symptoms and clinical signs makes it a mimicker of many other medical conditions⁴.

Initial misdiagnosis of ruptured Abdominal and dissecting Thoracic Aortic Aneurysms is common, and for dissection such delays have a significant adverse effect on survival.

Abdominal Aortic Aneurysm

Rupture of an Abdominal Aortic Aneurysm is initially misdiagnosed⁵ in up to a third of patients, usually as renal colic, diverticulitis, or gastrointestinal hemorrhage. The commonest clinical presentations in misdiagnosed cases are abdominal pain, shock and back pain.

However, the high mortality of ruptured Abdominal Aortic Aneurysm is not significantly increased by initial misdiagnosis, perhaps because those patients are better able to withstand delay.

Thoracic Aortic Dissection

The classic history for thoracic aortic dissection consists of the sudden onset of severe tearing or ripping chest pain radiating to the inter-scapular region (between the shoulder-blades) or low back, occurring in late middle-aged men with a history of hypertension⁶. The simple expedient of asking 3 standard questions about chest pain changed the probability of making a correct diagnosis from unlikely to very probable^{7,[Full-Text]}. The most discriminating clinical signs are absence or diminution of major pulses and neurological abnormalities⁸.

Practice Point

In missed thoracic aortic dissection look for

a history of chest pain
a) quality (tearing or ripping)

b) radiation (between shoulder-blades or to low back)

c) intensity at onset (severe)
comparison of the left and right major pulses
detailed neurological examination

In nearly 40% of hospitalised patients, diagnosis is delayed for more than 24 hours⁹, and such delays have a very significant effect on the probability of survival¹⁰.

Cerebral Aneurysm

Missing a sentinel bleed is a relatively common cause of viable medical malpractice litigation

Cerebral aneurysms occur in up to 6% of the population but in only 2% of those who have no risk factors for subarachnoid hemorrhage^11,[].

Rupture results in SubArachnoid Hemorrhage (SAH), pressure of which commonly causes permanent brain damage. Annual risk of rupture can be as high as 2% for aneurysms that are larger than 10 mm, but vast majority are smaller and have a considerably smaller probability of rupture.

If a cerebral aneurysm leaks only a little blood, a Thunderclap Headache may result. Nearly a half of headaches that are caused by such a sentinel bleed are misdiagnosed, usually as migraine, tension headache, the 'flu, sinusitis, or a "sprained neck"¹².