From the Guidelines
The normal diameter of the proximal ascending aorta in adults is approximately 3.4 cm for males and 3.0 cm for females, as measured by transthoracic echocardiography (TTE) 1.
Key Factors Influencing Aortic Diameter
- Age: The aorta naturally dilates with age at a rate of approximately 0.1 cm per decade.
- Sex: Men generally have slightly larger aortic diameters than women.
- Body size: Body surface area (BSA) influences aortic size, with larger individuals having proportionally larger aortas.
Diagnostic Considerations
When evaluating aortic dimensions, clinicians often index measurements to BSA for more accurate assessment.
- An ascending aorta is generally considered dilated when its diameter exceeds 4.0 cm.
- Surgical intervention may be considered when it reaches 5.0-5.5 cm, depending on other clinical factors 1.
Monitoring and Intervention
Regular monitoring with imaging such as echocardiography, CT, or MRI is recommended for patients with aortic dilation to track progression and determine appropriate timing for intervention.
- Aortic diameters greater than the upper limits of normal (2 SD above the mean diameter as adjusted for age, sex, and body surface area), but not meeting criteria for aneurysm, may be considered ectatic or dilated 1.
- The term aneurysm is reserved for diameters that are 150% of normal, which is approximately 5.0 cm for the ascending aorta 1.
From the Research
Normal Diameter of Proximal Ascending Aorta
The normal diameter of the proximal ascending aorta in adults can vary based on several factors including age, gender, and body size.
- According to a study published in 2009 2, the predicted aortic diameters for each patient based on the individual's age, gender, and body size were calculated at all four aortic positions using previously published regression equations derived from a large cohort of normal patients.
- A study from 2017 3 investigated the fate of a moderately dilated ascending aorta and found that the mean growth rate of the patients with a 40-44 mm, 45-49 mm, and ≥50 mm ascending aorta was 0.3 ± 0.5,0.3 ± 0.5, and 0.7 ± 0.9 mm/year, respectively.
- Another study from 2008 4 established the normal criterion of ascending aortic diameter measured by 64 multidetector computed tomography (MDCT) and electron beam computed tomography (EBT) based on gender and age, and found that the mean intraluminal AAOD was 31.1 ± 3.9 and 33.6 ± 4.1 mm in females and males, respectively.
Factors Influencing Aortic Diameter
Several factors can influence the diameter of the proximal ascending aorta, including:
- Age: The diameter of the ascending aorta increases with age 4.
- Gender: Males tend to have larger aortic diameters than females 4.
- Body size: The aortic diameter is related to body size, with larger individuals tend to have larger aortic diameters 2.
- Aortic valve disease: Patients with aortic valve disease, such as aortic stenosis or regurgitation, may have larger aortic diameters 5.
Clinical Implications
The diameter of the proximal ascending aorta has important clinical implications, particularly in relation to the risk of aortic dissection or aneurysm.
- A study from 2009 2 found that elective ascending aortic replacement is recommended to prevent acute type A aortic dissection when any segment of the proximal aorta is greater than 5.5 cm.
- Another study from 2017 3 found that patients with an aortic diameter ≥45 mm and aortic valve regurgitation were significantly associated with significant progression of aortic dilatation.