Aortic Aneurysm Expansion Index (AAEI) Calculator

Aortic Aneurysm Expansion Index (AAEI): Explanation and Clinical Context The Aortic Aneurysm Expansion Index (AAEI) quantifies the annual relative increase in aortic diameter, expressed as a percentage per year. It is calculated using the formula: (Follow-up Diameter - Baseline Diameter) / (Baseline Diameter × Time Interval) × 100%. AAEI helps clinicians identify patients at risk of rapid aneurysm growth and potential rupture.

Generally, an expansion rate greater than 10% per year is considered high risk and may warrant surgical or endovascular intervention, whereas rates below 5% per year are considered low risk and may be monitored with routine imaging. AAEI is particularly useful for both thoracic and abdominal aortic aneurysms and can guide follow-up intervals and timing of intervention. Factors influencing expansion include baseline aneurysm size, hypertension, smoking, connective tissue disorders, and age.