The incidence of aortic aneurysm increases with age. There is evidence that this condition is becoming more frequent. Aortic aneurysm has the potential to result in sudden and complete incapacitation.
Coming out of the heart, the thoracic aorta has a maximum dimension of 3.7 cm at the root, < 3.5-3.8 cm by the time it becomes the ascending aorta and 3.0 cm at the arch. The descending aorta's diameter should not exceed 2.5 cm. The normal size for the aorta depends on body surface area.
Aortic dilatation may remain static for long periods, particularly if causal factors such as hypertension have been well addressed. On average however, if aortic dilatation is present, the diameter is reported to increase by 1 mm per year for the ascending aorta, 3 mm for the descending thoracic aorta and 1.2 mm for the abdominal aorta. These figures are highly variable. However one cannot confidently determine the ascending aorta diameter better than within a 2 - 3 mm margin of error. This is true for echocardiography, MRI or CT as the measurement is technically difficult. This makes the assessment of diameter stability difficult.
For asymptomatic thoracic aneurysms, and those with bicuspid aortic valve, an ascending aorta diameter of 55 mm is generally an indication for intervention as the risk of the procedure becomes less than the risk of doing nothing. The threshold is 5.0 cm for patients with Marfan syndrome, and those with a family history of aortic dissection, but recent recommendations suggest a threshold of 5.5 cm for these patients also. Dissection may happen at smaller size and the risk of this occurring is not negligible.
Applicant with dilated aorta of 40 mm or more:
An applicant with a dilated ascending aorta diameter of less than 40 mm may be considered as having a condition that is not of aeromedical significance if: