Comparison of Diagnostic Parameters Using Cardiac CT–derived Aortic Valve Area and Aortic Valve Calcium Scores for Low-Gradient Aortic Stenosis

Purpose To compare the performance of cardiac CT-derived hybrid aortic valve area (AVA) and planimetry, in combination with aortic valve calcium (AVC) or AVC density (AVCd), for assessing low-gradient aortic stenosis (LGAS). Materials and Methods This retrospective analysis included patients with LGAS (mean gradient < 40 mm Hg) who underwent echocardiography and cardiac CT from November 2018 to March 2022. The performance of absolute and indexed hybrid AVA and planimetry, combined with either absolute AVC or AVCd, was compared by time-to-event analysis and outcome classification ability. Results A total of 215 patients (mean age, 79.2 years ± 8.4 [SD]; 118 male patients) were included in the study. Of these, 74.4% (160 of 215) experienced a composite outcome of valve intervention or all-cause mortality during follow-up. Specifically, 11% (23 of 215) underwent surgical aortic valve replacement, 59% (126 of 215) underwent transcatheter aortic valve replacement, and 15% (32 of 215) died. The median follow-up duration was 478 days (IQR, 283-716 days). Indexed AVA measures performed better than absolute AVA. All models showed comparable discrimination, as measured by Harrell C statistic. The highest performing model was indexed AVA calculated using left ventricular outflow tract area derived from minimum CT diameter combined with absolute AVC (hazard ratio, 2.29; 95% CI: 1.66, 3.15; <i>P</i> < .001; C statistic, 0.60). The lowest performing model was absolute AVA planimetry with AVCd (hazard ratio, 1.62; 95% CI: 1.19, 2.22; <i>P</i> = .002; C statistic, 0.55). Conclusion Diagnostic strategies involving hybrid AVA and AVC or AVCd demonstrated comparable performance in LGAS assessment. Indexed hybrid AVA measures performed better alone or in combination with AVC compared with the absolute AVA measures. <b>Keywords:</b> Aortic Valve Calcium, Cardiac CT, Low-Gradient Aortic Stenosis <i>Supplemental material is available for this article.</i> © RSNA, 2025.