Aorta (Ao)
Aortic Root
The aortic root is the most commonly measured aortic dimension. If only one aortic measurement is reported, it almost always refers to the aortic root and is often abbreviated Ao. A useful rule of thumb for beginners is that the aortic root diameter should generally not exceed 4 cm.
To measure the aortic root, first freeze the 2D image using the Freeze button. Then use the trackball to move to the end-diastolic frame, where the aortic valve is closed.
Figure: Aortic root measurement from the 2D image. The measurement is performed with the aortic valve closed (end-diastole).
Video: Measurement of the aortic root and left atrium from the parasternal long-axis view.
Other Aortic Dimensions
Like the aortic root, the ascending aorta is measured at end-diastole.
Figure: Sinotubular junction and ascending tubular aorta. Measurements are performed at end-diastole.
Video: Measurement of the ascending aorta. Notice how the aorta moves closer to the top of the image during systole and closer to the bottom during diastole. In this video, the measurement is performed in early diastole, although current guidelines recommend measuring the ascending aorta in end-diastole.
Measurement Technique
According to recommendations from ASE and EACVI, aortic dimensions should be measured using the leading edge-to-leading edge principle. For clarity, however, this guide presents all 2D diameter measurements using the inner edge-to-inner edge principle. A detailed discussion of these measurement principles is beyond the scope of this guide. Readers interested in the topic are referred to the article by Oxborough and colleagues.
According to current recommendations, only the aortic annulus is measured in mid-systole, whereas all other aortic dimensions are measured at end-diastole. No specific recommendation is provided for measuring the aortic arch. In routine echocardiography, measuring the aortic root is usually sufficient. Other aortic dimensions are most commonly measured when aortic dilatation is suspected or being followed.
| Aortic Dimension | Timing | When to Measure |
|---|---|---|
| Aortic annulus | Mid-systole | For example, before TAVI |
| Aortic root | End-diastole | Always |
| STJ | End-diastole | At least if aortic dilatation is present |
| ATA | End-diastole | At least if aortic dilatation is present |
| Aortic arch | (no recommendation) | At least if aortic dilatation is present |
| Abbreviations: | ||
| STJ, sinotubular junction. ATA, ascending tubular aorta. |