From the Guidelines
The size of the ascending aorta is typically considered in relation to the patient's height, with a maximal cross-sectional area to height ratio of ≥10 cm2/m being a threshold for prophylactic aortic root replacement. When evaluating the size of the ascending aorta, it's essential to consider factors such as age, sex, height, and body size, as these can influence aortic diameters and the risk of aortic events, including dissection 1.
Key Considerations
- Aortic event rates increase as the aortic size indexed to height or body size increases
- The maximal cross-sectional area of the aortic root or ascending aorta divided by the patient's height is a critical factor in determining the need for prophylactic surgery
- A ratio of ≥10 cm2/m is considered a reasonable threshold for prophylactic aortic root replacement, as it has been associated with favorable outcomes 1
Clinical Implications
- Regular monitoring and assessment of the ascending aorta are crucial, particularly in individuals with risk factors for aortic disease
- The use of imaging studies such as echocardiography, CT, or MRI can help track changes in aortic size and guide clinical decision-making
- Surgical intervention may be necessary when the ascending aorta reaches a certain size or when the risk of aortic events is deemed high, and the maximal cross-sectional area to height ratio can inform this decision 1
From the Research
Size of the Ascending Aorta
The size of the ascending aorta can vary among individuals. According to a study published in 2015 2, the mean ascending aortic diameter of the reference population was 3.2 cm (±0.4 cm). The largest diameter was 4.9 cm in women and 5.0 cm in men.
Distribution of Ascending Aortic Size
The distribution of ascending aortic size is as follows:
- The proportion of subjects with an aorta <3.5 cm was 79.2%
- The proportion of subjects with 3.5-3.9 cm was 18.0%
- The proportion of subjects with 4.0-4.4 cm was 2.6%
- The proportion of subjects with ≥4.5 cm was 0.22% 2
Threshold for Surgery
Current guidelines recommend a diameter of 5-5.5 cm as the threshold for surgery on the ascending aorta 2. However, other studies suggest that the threshold for surgery may be lower, especially for patients with certain risk factors 3, 4.
Factors Affecting Aortic Size
Several factors can affect aortic size, including:
- Age: Advancing age makes the aorta more vulnerable, increasing the likelihood of dissection 5
- Sex: Female sex confers some increased risk, which can be largely accommodated by using body-size-based nomograms 5
- Body surface area: Aortic diameter should be placed in context vis-a-vis the normal distribution in the general population with similar sex, age, and body surface area 4
- Aortic valve disease: Patients with aortic regurgitation had a tendency to faster aortic dilation compared to those with aortic stenosis 3
- Genetic aberrations: Specific genetic aberrations provide a powerful predictor of aortic behavior; malignant genetic variants obligate earlier surgery 5
- Family history: Aortic events closely follow those in relatives with a threefold increase in likelihood of aortic dissection for other family members once an index family dissection has occurred 5