Predictors of Transannular Patch Enlargement in Tetralogy of Fallot Repair; a Single Center Experience

Introduction: Tetralogy of Fallot (ToF) accounts for 5% to 10% of all congenital heart diseases (CHD) and is the commonest cyanotic heart disease beyond the neonatal period. Surgical repair is directed at relieving the right ventricular outflow tract obstruction (RVOTO) and has evolved over time from the frequent use of transannular patch enlargement (TAPE) of the pulmonary valve annulus (PVA), to the more recent trend of conservation of the PVA using valve-sparing surgical techniques. This is latter technique is preferred to avoid serious and progressive complications associated with TAPE. The decision on TAPE is primarily base on the PVA z-score which is subject to variability across different surgeons and centers; as such, other parameters have been proposed and some determined to be better predictors of TAPE in ToF surgeries. Aim: To determine the predictors of transannular patch enlargement in ToF surgeries in a CHD specialist center. Methods: This was a retrospective analysis of all patient with ToF who presented at a major CHD center - the Sri Sathya Sai Sanjeevani Hospital (SSSSH), in Raipur India between July 2018 to April 2019. Parameters sought and obtained included patients’ demographics, anthropometry and echocardiographic parameters. The z-scores and other derivable variables were calculated and entered into a data base. Analysis using SPSS was done. Descriptive statistics was used to represent continuous variables in means, medians and ranges while categorical variables were represented in bar chats. Analysis of variance was done among group means. Results: There were 135 patients with age range from 7months to 199 months, with more males 89 (65.9%). TAPE was done in 36(26.7%). The aortic valve diameter (18.3 Vs 20mm, p=0.037), Pulmonary valve diameter (10.1 vs 12.0mm, P=0.003), and pulmonary valve Z-score (-2.48 vs -1.47, p=0.011) were significantly smaller for the group that received TAPE. Univariate analysis of the great artery ratio (PVA/AoV) did not significantly predict TAPE use. However, a GA ratio of < 0.54 was significantly associated with a higher likelihood of having TAPE, odds ratio 2.37(CI: 1.47 to 3.9). Multivariate logistic for use of TAPE in TOF explained 15% (R2) of the variance seen in the use of TAPE and correctly predicted 70.8% of the children with TOF who received TAPE. The area under curve for predictability of who received TAPE was 65% (95% CI 53.5% to 76.6. Conclusion: The PVA diameter, Aortic valve diameter and PVA z-score are predictors of TAPE. A GA ratio < 0.54 increases the likelihood of TAPE. Clinical parameters are not useful as determinants of TAPE.