What is the recommended method for measuring the sinus of Valsalva?

Sinus of Valsalva Measurement: Recommended Methods

For echocardiography, measure the sinus of Valsalva at its maximal diameter at end-diastole using the leading-edge to leading-edge (L-L) convention from the parasternal long-axis view, while CT and MRI should use inner-edge to inner-edge (I-I) measurements with consistent sinus-to-sinus or sinus-to-commissure approaches. 1

Echocardiographic Measurement Technique

Timing and Imaging Plane

• Measure at end-diastole (not systole, which is reserved only for the aortic annulus measurement). 1
• Obtain measurements from the parasternal long-axis view that depicts the aortic root and proximal ascending aorta—this plane differs slightly from the standard left ventricular long-axis view. 1
• The measurement plane must be strictly perpendicular to the long axis of the aorta to capture the maximum diameter accurately. 1

Measurement Convention

• Use the leading-edge to leading-edge (L-L) convention for echocardiography, measuring from the outer anterior wall to the inner posterior wall. 1, 2
• This L-L convention provides measurements that are 2-4 mm larger than the inner-edge to inner-edge method used by CT/MRI. 1, 2
• The L-L convention was maintained for echocardiography (despite attempts to standardize across modalities) because all established reference values and surgical thresholds are based on this method. 1

Technical Considerations

• Use simultaneous biplane orthogonal images from matrix transducers when available to ensure proper plane selection. 1
• Verify correct imaging plane by checking that the closure line of the aortic leaflets is centered in the aortic root lumen—an asymmetric closure line indicates the cross-section is not capturing the largest diameter. 1
• If the ascending aorta is not well visualized from standard windows, move the transducer closer to the sternum or try right parasternal windows in the second or third intercostal space. 1

CT and MRI Measurement Technique

Measurement Convention

• Use inner-edge to inner-edge (I-I) measurements for both CT and cardiac MRI. 1
• Measurements can be obtained using either sinus-to-sinus (S-S) or sinus-to-commissure (S-C) approaches, but consistency is mandatory for serial surveillance. 1

Technical Approach

• Obtain reformatted images orthogonal to the aortic root at the level of the sinuses of Valsalva. 1
• Use double-oblique reconstruction to ensure measurements are perpendicular to the aortic long axis and avoid overestimation from oblique slices. 2
• Measure all three sinuses consistently using the same approach (sinus-to-sinus or sinus-to-commissure) for comprehensive assessment. 1

TAVR-Specific Measurements

For transcatheter aortic valve replacement planning, the approach differs significantly:

• Measure the aortic annulus at mid-systole using inner-edge to inner-edge convention (not L-L). 1
• Use 3D echocardiography with multiplanar reconstruction or CT for direct planimetry of the annular area, as this provides superior accuracy compared to 2D diameter measurements. 1
• The sinus of Valsalva diameter requirements are valve-specific: ≥27 mm for 26-mm valves and ≥29 mm for 29-mm and 31-mm valves. 1

Comparison Across Modalities and Clinical Implications

Understanding Measurement Discrepancies

• TTE consistently underestimates maximum aortic root diameter compared to both CTA and MRA, contrary to what the measurement convention differences would predict. 2
• This underestimation occurs despite the L-L convention theoretically providing larger measurements, due to technical factors including limited acoustic windows, oblique imaging planes, and cardiac motion artifacts. 2

Serial Monitoring Recommendations

• Use the same imaging modality with the same measurement method for all follow-up studies to ensure accurate assessment of progression (Class I recommendation). 1, 2
• If TTE shows an increase of ≥3 mm per year, obtain confirmation with CTA or MRI before making surgical decisions. 2
• For patients with measurements near surgical thresholds, do not rely solely on TTE—obtain cross-sectional imaging for surgical planning. 2

Reference Values and Indexing

• Compare measurements to age- and body surface area (BSA)-related nomograms using published allometric equations. 1
• Normal values for sinuses of Valsalva: 3.4 ± 0.3 cm in men, 3.0 ± 0.3 cm in women (absolute values). 1
• Indexed values: 1.7 ± 0.2 cm/m² in men, 1.8 ± 0.2 cm/m² in women. 1
• Aortic dilatation is defined as diameter above the upper limit of the 95% confidence interval for the reference population. 1

Common Pitfalls to Avoid

• Never assume TTE overestimates aortic size—evidence shows it underestimates compared to CT/MRI despite using the L-L convention. 2
• Avoid oblique imaging planes that can cause significant measurement errors in all modalities. 2
• Do not switch measurement conventions between follow-up studies, as this will create artificial changes in measured dimensions. 1, 2
• For comprehensive pre-surgical assessment, particularly for the aortic root and ascending aorta, ECG-triggered CTA is recommended over TTE alone. 2