PREOPERATIVE CARDIAC CT ASSESSMENT OF THE PULMONARY ANNULUS AND RIGHT VENTRICULAR OUTFLOW TRACT IN TETRALOGY OF FALLOT: A RETROSPECTIVE STUDY WITH SURGICAL CORRELATION

Abstract

Background: Accurate preoperative characterization of the pulmonary valve annulus and right ventricular outflow tract (RVOT) is important in tetralogy of Fallot (TOF), particularly when assessing the likelihood of transannular enlargement at repair. Cardiac CT permits standardized multiplanar evaluation of pulmonary annular and RVOT morphology while simultaneously delineating pulmonary arterial, coronary, aortic arch, and collateral vascular anatomy. Objective: To evaluate preoperative cardiac CT-derived pulmonary annular and RVOT parameters in TOF and assess their association with transannular patch (TAP) placement at definitive surgical repair. Methods: This single-center retrospective observational study included all 26 eligible patients aged ≤10 years with TOF available in the institutional cardiac CT database between June 2025 and May 2026 who subsequently underwent complete surgical repair with documented TAP status. Pulmonary valve (PV) annular minimum and maximum diameters and area were measured on a standardized en-face double-oblique annular plane. PV Dmin Z-scores were derived using the CT specific pediatric reference of Soszyn et al. with Haycock body surface area (BSA). The predefined principal CT variables were PV Dmin Z-score, PV-to-aortic annular minimum-diameter (PV/Ao Dmin) ratio, and minimum RVOT diameter. Operative TAP placement served as the surgical endpoint. Between-group comparisons and receiver operating characteristic (ROC) analysis with stratified bootstrap confidence intervals were performed. Multivariable modeling was not undertaken because of the limited sample size. Results: Seventeen patients (65.4%) underwent TAP placement and nine (34.6%) underwent non-TAP repair. The TAP group had a smaller PV Dmin (10.10 ± 1.87 vs 12.19 ± 2.37 mm; p=0.039), a more negative PV Dmin Z-score (−2.51 ± 0.65 vs −1.50 ± 0.85; p=0.008), and a lower PV/Ao Dmin ratio (0.505 ± 0.065 vs 0.637 ± 0.049; p<0.001). Minimum RVOT diameter was smaller in the TAP group but did not differ significantly (5.28 ± 1.39 vs 6.17 ± 1.04 mm; p=0.080). PV/Ao Dmin ratio demonstrated the highest observed discrimination for TAP placement (AUC 0.961; 95% bootstrap CI 0.863–1.000), followed by PV Dmin Z-score (AUC 0.837) and minimum RVOT diameter (AUC 0.706). Conclusion: Pulmonary annular hypoplasia on preoperative cardiac CT was associated with TAP placement. PV/Ao Dmin ratio and the CT-derived PV Dmin Z-score demonstrated the strongest discriminatory performance, whereas minimum RVOT diameter alone was less informative. Cardiac CT should be interpreted as an integrated quantitative and morphological tool supporting surgical planning rather than as a stand-alone operative decision method.