Measure the aortic annulus in systole (area, perimeter, diameters), the coronary ostial heights, sinus and sinotubular dimensions, valve calcification, and the iliofemoral access calibre — the numbers that choose the valve size and route.
Orient first
- The annulus is a virtual ring at the hinge points of the leaflets — measured on a double-oblique plane.
- Low coronary heights (< 10–12 mm — verify) and a small sinus raise the risk of coronary obstruction.
- Minimum iliofemoral lumen diameter guides transfemoral access (device-specific).
Acquire the study
- ECG-gated CT angiography of the aortic root (systolic phase ~30–40% for the annulus, full cycle if possible), then non-gated CTA of the aorta to the femoral arteries.
The manoeuvre
- Double-oblique plane at the three hinge points: annulus area in mm², perimeter in mm, minimum and maximum diameters.
- Coronary ostial heights above the annulus in mm (left and right).
- Sinus of Valsalva diameters and sinotubular junction diameter in mm.
- Calcification of leaflets and left ventricular outflow tract (annular rupture risk).
- Iliofemoral arteries: minimal lumen diameter in mm, tortuosity, calcification on curved reformats.
- Fluoroscopic projection angle perpendicular to the valve.
What confirms it
- A complete measurement set consistent across phases.
What licenses you to exclude it
- Access vessels below the device threshold exclude transfemoral access — name alternative routes.
The classic misread
- Measuring the annulus in diastole or on an axial slice.