From the Guidelines
The normal size of the ascending thoracic aorta is typically considered to be between 3.5 and 4.0 cm in diameter, as stated in the ACR Appropriateness Criteria for suspected thoracic aortic aneurysm 1. When evaluating the size of the ascending thoracic aorta, it's essential to consider individual variations based on age, gender, and body size.
- The aortic diameter decreases in size as it courses distally, with larger diameters seen particularly in older males 1.
- Aortic dilatation of <50% over normal qualifies as aortic ectasia, whereas thoracic aortic aneurysms (TAAs) are diagnosed when there is at least 50% enlargement of the aortic lumen, or alternatively when the aortic diameter is more than two standard deviations above the mean for the patient’s sex and age 1.
- The most common locations for TAA are in the ascending aorta, followed by the descending aorta, and are seen in similar incidence in the aortic arch and thoracoabdominal aorta 1. Regular monitoring is recommended for individuals with borderline measurements or risk factors for aortic disease, as an enlarging aorta may indicate developing pathology such as aneurysm formation.
- Larger aneurysms that reach >5 cm in diameter, and TAAs that increase in size >0.5 cm per year, trigger an evaluation for possible intervention due to their association with increased morbidity and mortality 1. Maintaining healthy blood pressure and avoiding tobacco are important preventive measures for aortic health.
- Clinicians typically use imaging studies such as echocardiography, CT scans, or MRI to evaluate aortic size, and body surface area (BSA) is often used to index aortic measurements for more personalized assessment 1.
From the Research
Normal Size of the Ascending Thoracic Aorta
The normal size of the ascending thoracic aorta can vary depending on several factors such as age, sex, and body surface area.
- According to 2, the normal distribution of the ascending aortic diameter in the general population can be used to determine personalized risk stratification for patients with ascending aortic aneurysms.
- The study found that the risk of adverse aortic events increases when the aortic diameter exceeds a certain threshold, which can be calculated based on the patient's sex, age, and body surface area.
- For example, a 75-year-old male with a body surface area of 2.1 m2 would be at increased risk of adverse events if the root diameter exceeds 5.15 cm or the mid-ascending diameter exceeds 5.27 cm.
Diagnostic Criteria
The diagnosis of thoracic aortic aneurysms is typically made using imaging techniques such as:
- Computed tomography angiography (CTA) 3
- Echocardiography 4, 5
- Magnetic resonance imaging (MRI) 3
- Positron emission tomography (PET) 3
- The gold standard for aneurysm evaluation is CTA, which allows for precise diameter assessment and accurate preoperative planning.
Treatment Strategies
The treatment of thoracic aortic aneurysms depends on the diameter of the aneurysm and the presence of symptoms.
- Elective treatment is recommended for aneurysms with a diameter > 55 mm 3
- Endovascular repair is associated with lower perioperative morbidity and mortality rates compared to open surgery 3
- Open surgery is typically reserved for young patients who are fit for surgery 3
- Hybrid procedures, such as debranching of supra-aortic vessels and TEVAR, are also used to treat aneurysms involving the aortic arch 3