Aortic Diameter Guidelines

Normal Aortic Diameters

The normal diameter of the ascending thoracic aorta in adults ranges from 2.5-3.8 cm, with men having larger diameters (3.4-3.9 cm) than women (3.0-3.5 cm), and the aortic root diameter is approximately 3.63-3.91 cm (±0.38 cm) 1, 2, 3
The proximal ascending aorta diameter is approximately 2.9 ± 0.3 cm, and men have larger aortic diameters than women by 1-3 mm 2, 4, 1
The normal ascending aorta diameter in an 80-year-old male is approximately 3.7-4.4 cm, with an upper normal limit of 4.5 cm 4, 1

The aorta naturally dilates with age at a rate of approximately 0.12-0.29 mm per year, and body mass index affects aortic diameter by approximately 0.27 mm per unit of BMI 1, 4
Body size and gender are factors that influence aortic diameter, with body mass index and gender affecting aortic diameter by approximately 0.27 mm per unit of BMI and 1-3 mm, respectively 4, 1

Aortic diameters greater than the upper limits of normal (2 standard deviations above the mean) but not meeting aneurysm criteria are considered ectatic or dilated, and an aneurysm is defined as a diameter that is 150% of normal, which is approximately 5.0 cm for the ascending aorta and 4.0 cm for the descending aorta 3
For patients with connective tissue disorders like Marfan syndrome, intervention may be considered at smaller diameters (5.0 cm), and the American College of Cardiology and other guideline societies may recommend surgical intervention at 5-5.5 cm for the ascending aorta 3, 4, 1

Measurements should be made perpendicular to the axis of blood flow, from outer wall to outer wall, and specify the exact location of measurement (e.g., sinus of Valsalva, sinotubular junction, mid-ascending aorta) 4, 1
Different imaging modalities may yield slightly different measurements, with CT and MRI measurements from sinus to commissure generally being smaller than echocardiographic measurements from sinus to sinus 5
Regular monitoring is recommended when aortic dimensions approach upper normal limits, although the exact frequency and modality may depend on individual patient factors and guideline recommendations 4, 1