Accuracy of device landing zone calcium volume measurement with contrast-enhanced multidetector computed tomography

The extent of aortic valve calcification is an important determinant of procedural success in transcatheter aortic valve implantation (TAVI). We sought to validate device landing zone calcium volume (DLZ-CV) measurements on contrast-enhanced multidetector computed tomography (MDCT) with non-contrast-enhanced scans as reference.

We determined DLZ-CV in 141 patients undergoing transfemoral TAVI. Non-contrast-enhanced images were analyzed using a threshold of 130 HU as reference (DLZ-CV₁₃₀). For contrast-enhanced scans, we applied various thresholds including 450 HU (DLZ-CV₄₅₀), 850 HU (DLZ-CV₈₅₀), mean aortic attenuation (Atten_Ao) + 2 SD (DLZ-CV_2SD), Atten_Ao + 4 SD (DLZ-CV_4SD), Atten_Ao + 4 SD + 5 mm³ volume filter (DLZ-CV_4SD+), and based on visual estimation (DLZ-CV_vis). We compared DLZ-CV values between patients with versus without paravalvular leak (PVL), and between patients with versus without post-dilatation stratified by the type of prosthesis.

All DLZ-CV measurements on contrast-enhanced scans significantly differed from DLZ-CV₁₃₀ (p < 0.001 for all comparisons). The best approximation to DLZ-CV₁₃₀ was achieved with DLZ-CV_4SD+ (508 mm³ [332-772]; Pearson correlation: R = 0.87, p < 0.001; Bland-Altman: mean difference 1339 mm³ [limits of agreement 79;2600]). Moreover, DLZ-CV_4SD+ allowed for discrimination of PVL ≥1° or the need for post-dilatation in patients receiving self-expanding prostheses. Procedural outcome using balloon-expandable prostheses was independent of DLZ-CV.

Measurement of DLZ-CV using contrast-enhanced scans with unadjusted thresholds results in incorrect estimation of the calcium volume. The use of a scan-specific individual HU threshold including a volume filter (DLZ-CV_4SD+) provides the best approximation to the reference and allows for discrimination of PVL ≥ 1° in patients receiving the Acurate neo prosthesis.