Aortic Size Distribution in the General Population: Explaining the Size Paradox in Aortic Dissection

Area of Science:

• Cardiovascular Medicine
• Radiology
• Epidemiology

Background:

• Current guidelines recommend ascending aorta surgery at 5-5.5 cm diameter.
• A previous study noted dissections occurring at <5.5 cm, termed the 'aortic size paradox'.
• The population at risk for dissection at smaller aortic sizes was previously unknown.

Purpose of the Study:

• To calculate the relative risk of aortic dissection at ascending aorta sizes below 5.5 cm.
• To analyze the number of dissections and the population at risk for each aortic size.
• To investigate the underlying causes of the aortic size paradox.

Main Methods:

• Utilized a database of 3,573 individuals from the general population.
• Assessed ascending aortic size distribution using magnetic resonance imaging.
• Calculated relative risk by dividing dissection proportion by population proportion for each aortic size.

Main Results:

• The mean ascending aorta diameter was 3.2 cm; the largest were 4.9 cm (women) and 5.0 cm (men).
• Relative risk of dissection increased significantly with aortic size, from 0.055 (<3.5 cm) to 346.8 (≥4.5 cm).
• Individuals with aortas ≥4.5 cm were 6,305 times more likely to experience dissection than those with aortas <3.5 cm.

Conclusions:

• The 'aortic size paradox' is an artifact of large populations with smaller aortas.
• Normal ascending aorta diameters are typically smaller than the surgical threshold.
• Findings support current surgical intervention guidelines for ascending aorta diameters of 5-5.5 cm.