Aortic annulus sizing: echocardiographic versus computed tomography derived measurements in comparison with direct surgical sizing.
OBJECTIVES
The precise sizing of the aortic annulus is crucial in order to select the most appropriate valve size for transcatheter aortic valve implantation (TAVI). Owing to the closed heart situation in TAVI, sizing has to be performed based on preoperative imaging when compared with direct sizing during conventional procedures. The aim of the study was to evaluate valve sizing performed either by CT-scan or by echocardiography by comparing these imaging-based measurements with direct intraoperative sizing.


METHODS
Prior to the standard conventional aortic valve replacement, 26 patients underwent cardiac CT-scan and echocardiographic examination. Maximal annular diameter was measured by echocardiography at end-diastole and end-systole, including the leaflet calcifications. The CT-scan maximal, minimal and mean diameters were measured as well as the 'effective' diameter (CT(eff)). CT(eff) represents the diameter of a circle with the exact same area as the measured area of the annular circumference reconstructed from the CT-data set. Direct intraoperative diameters were measured after decalcification using metric sizers.


RESULTS
CT(eff) and end-systolic echocardiographic diameters showed best agreement with intraoperative direct sizing (intraop) in the Bland-Altman analysis [mean difference for transoesophageal echocardiography (TEE) vs intraop 0.5 mm (limits of agreement -2.5-3.5); mean difference for transthoracic echocardiography (TTE) vs intraop 0.38 mm (limits of agreement -3.28-4.03) and CT(eff) vs intraop -0.56 (limits of agreement -3.16-2.05)]. In patients with an oval-shaped annulus, CT(eff) demonstrated the best agreement with intraop [mean difference -0.32 (limits of agreement -2.29 to 1.66)].


CONCLUSIONS
Both the 'effective' CT diameter and end-systolic TEE values are the most reliable approaches for preoperative aortic annulus sizing. In patients with a pronounced oval-shaped annulus, the 'effective' CT diameter seems to be the method of choice. Therefore, aortic annulus measurement using 'effective' CT diameters should be included into current recommendations for TAVI sizing.