Abdominal Aortic Aneurysm (AAA) Prognosis Calculator

AAAs medical guidelines

The AAA calculator above uses the aortic dilatation size to prognosticate the predicted average annual expansion rate, absolute lifetime risk of rupture and clinical recommendation.

The method applies to aneurysms of sizes from 3 cm to 7 cm and above in incremental steps of 0.10 cm.

For example, in the case of an aneurysm of 4.4 cm, the answer provided will consist of:

■ Predicted Average Annual Expansion Rate: 3 to 5 mm;

■ Absolute Lifetime Risk of Rupture: 20%;

■ Clinical Recommendation: Ultrasonography or Computed Tomography every 6 to 12 months plus considering surgical consultation.

Enlargement of the abdominal aorta to 3 cm diameter or more is caused by a degeneration of the media portion, the middle layer of the arterial wall.

This is caused by atherosclerosis hardening or other even natural wear and tear with age. The dilatation is gradual and does not stop naturally.

The patient category at highest risk is men older than 65 of age. Patients with peripheral atherosclerotic vascular disease are at increased risk of developing an AAA.

Most aortic aneurysms are only diagnosed at an advanced state because they don’t have any accompanying symptoms until the point they reach vast expansion or rupture.

Expanding abdominal aneurysms may be palpable during physical exams. They are also characterized by sudden, severe low back pain, pain in flank or groin.

Local compression may lead to nausea, vomiting or venous thrombosis.

Diagnostic is performed through imagistic means such as:

■ Computed tomography (CT);

■ Ultrasonography;

■ Magnetic resonance imaging (MRI);

■ Angiography;

■ Plain radiography.

When the artery wall stress exceeds the strength of the vascular wall, the rupture produces.

Presentation with ruptured aneurysm is characterised in most cases by cyanosis, tachycardia, hypotension and altered mental status.

However, there are also cases in which vital signs remain in norms because the hematoma is contained retroperitoneally.

Small aneurysms that are associated with high blood pressure may be recommended drug therapy with beta blockers.

The main repair method is surgery (elective or emergency), either open surgery with transperitoneal or retroperitoneal approach or endovascular repair with a graft.

Abdominal aortic aneurysm prognosis

Prognosis in AAAs is largely dependent on the size and location of the aneurysm but also on other patient risk factors and cardiovascular condition.

The size of an aneurysm expands at a rate of 10% per year. The higher the diameter size, the higher the risk of rupture.

Its size can be determined via finite element method (FEM), rupture potential index (RPI) and the finite element analysis rupture index (FEARI) or the analysis of geometrical parameters during CT.

Elective surgery reduces the risk of rupture and rebuilds the affected aortic region. Complications of this type of surgery are relatively low compared to other cardiac surgery.

Aneurysm ruptures result in deadly hemorrhage in 80% of cases and in case the patient survives to reach the ER unit and does not die of sudden cardiovascular collapse, urgent surgery has a rate of 50% success.

Survival rate is lower than 45% in most ruptured AAAs and intervention needs to be very rapid as survival chances are said to drop with 1% per minute.

Long term prognosis with AAA is correlated with associated comorbidities such as chronic heart failure or chronic obstructive pulmonary disease.

References

1. Hirsch AT et al. ACC/AHA 2005 guidelines for the management of patients with peripheral arterial disease. J Am Coll Cardiol. 2006; 47(6):1239-312. 

2. Lederle FA, Kane RL, MacDonald R, Wilt TJ. Systematic review: repair of unruptured abdominal aortic aneurysm. Ann Intern Med. 2007; 146(10):735-41. 

3. Gadowski GR, Pilcher DB, Ricci MA. Abdominal aortic aneurysm expansion rate: effect of size and beta-adrenergic blockade. J Vasc Surg. 1994; 19(4):727-31.