Performance of Computed Tomography Angiography (CTA) for the Diagnosis of Hypo-Attenuated Leaflet Thickening (HALT).

(1) Background: Early hypo-attenuated leaflet thickening (HALT) is diagnosed by computed tomography angiography (CTA) in approximately 15% of patients undergoing transcatheter aortic valve replacement (TAVR). We sought to investigate the diagnostic performance of CTA for the diagnosis of HALT, focusing on timing data assessment within the cardiac cycle. (2) Methods: The study enrolled 50 patients with and 50 without HALT with available post-TAVR-CTA. The primary objective was to compare the diagnostic performance of CTA readings at specific intervals and time points during the cardiac cycle (entire systole, entire diastole, end-systole, and mid-diastole) versus gold standard (consensus reading by two observers based on multiphase full cardiac cycle data sets). (3) Results: 100 CTAs were independently analysed by two observers blinded to clinical characteristics of the study population and the results from the gold standard reading. Sensitivity and specificity for the diagnosis of HALT were 84%/94% in systole, 87%/92% in diastole, 78%/95% at end-systole, and 80%/94% at mid-diastole. End-systole had the highest positive predictive value (0.88) and positive likelihood ratio (36). Cohen's kappa for interobserver reliability was 0.715 in systole, 0.578 in diastole, 0.650 at end-systole, and 0.517 at mid-diastole. (4) Conclusion: Limiting CTA reading to distinct intervals or time points during the cardiac cycle has good specificity but lowers sensitivity. For a reliable diagnosis of HALT, data sets from a multiphase CTA covering the entire cardiac cycle should be analysed. A double reader approach would be desirable in further studies investigating HALT.