Key result
An 850 HU threshold on contrast CT correlates best with Agatston aortic calcium scores.
Why the study?
Evaluating aortic valve calcium burden is important when planning TAVI, but a standard reference for calcium assessment on contrast-enhanced CT series is lacking.
What is the optimal Hounsfield Unit threshold for evaluating aortic valve calcium volume on contrast-enhanced CT scans compared to noncontrast-enhanced Agatston scores in TAVI patients?
Observational (n=244)
What is the optimal Hounsfield Unit threshold for evaluating aortic valve calcium volume on contrast-enhanced CT scans compared to noncontrast-enhanced Agatston scores in TAVI patients?
Effect estimate: r = 0.45
p-value: p=< 0.0001
The optimal threshold for aortic valve calcium evaluation on contrast-enhanced CT depends on LVOT contrast enhancement, with 450 HU recommended for LVOT <300 HU and 850 HU for LVOT ≥300 HU.
May support individualized HU thresholds by LVOT enhancement for aortic calcium quantification in TAVI; leaves open prospective outcome validation.
BACKGROUND: The evaluation of aortic valve calcium burden is important when planning for transcatheter aortic valve implantation (TAVI). Although a robust golden standard methodology is available for calcium evaluation on noncontrast-enhanced (NCE) computed tomographic (CT) series, a standard reference for calcium assessment on contrast-enhanced CT series is currently lacking. METHODS: Two hundred and forty-four preprocedural CT scans from patients who had received TAVI were analysed. We correlated the aortic calcium volumes obtained on CE series at three thresholds [450, 850, and 'probe + 100' Hounsfield Units (HU)] with the Agatston score obtained on NCE scans. A subgroup analysis was performed taking into account the contrast enhancement of the left ventricular outflow tract (LVOT), with a prespecified cut-off of 300 HU. RESULTS: The overall population analysis showed higher correlation with the Agatston score using the 850 HU threshold (r = 0.45, P < 0.0001); no correlation was found with the 450 HU threshold, whilst the 'probe + 100' HU threshold showed a weaker correlation (r = 0.30, P < 0.0001). In patients with LVOT enhancement less than 300 HU, 450 HU showed the highest accuracy in calcium identification (r = 0.70, P < 0.0001), whereas in patients with LVOT enhancement of at least 300 HU, the most accurate threshold was 850 HU (r = 0.46, P < 0.0001). CONCLUSION: The thresholds for correct calcium identification using the automatic 3Mensio software depend on the contrast enhancement of aortic and cardiac structures, which can be estimated by measuring the HU in the LVOT. In patients with LVOT HU of less than 300, the correct threshold to be set in the software is 450 HU, whereas in patients with LVOT HU of at least 300 the correct threshold is 850 HU.
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Angelillis et al. (2020) conducted an observational in Aortic valve stenosis (n=244). Calcium volume evaluation on contrast-enhanced CT series vs. Agatston score on noncontrast-enhanced scans was evaluated on Correlation of aortic calcium volumes on contrast-enhanced series with Agatston score on noncontrast-enhanced scans (r = 0.45, p=< 0.0001). Aortic calcium volume evaluation on contrast-enhanced CT using an 850 HU threshold correlated best with Agatston score overall (r=0.45, P<0.0001), though optimal thresholds depend on LVOT enhancement.
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