Optimal Use of Z-Scores to Preserve the Pulmonary Valve Annulus During Repair of Tetralogy of Fallot.

OBJECTIVE: The size of the pulmonary annulus measured as a z-score is often used to determine when to insert a transannular patch (TAP). Multiple "cutoffs" are quoted in the literature; this could lead to inappropriate insertion. We aimed to determine whether the use of z-scores derived from different populations may have contributed to the varied "cutoffs" quoted.

METHODS: PubMed was searched using the terms: "tetralogy," "Fallot," "transannular," "patch," "mortality," and "death." Studies published between January 1, 2005, and October 5, 2017, were included; studies without participants under the age of 18 years and studies that did not describe the operative procedure were excluded.

RESULTS: Of 52 papers retrieved, 19 were included representing 2,500 repaired patients; 1,371 (54.8%) had a TAP. Five (26.3%) papers representing 638 patients (25.5%) quoted a z-score "cutoff" and what data set was used; "cutoffs" ranged from -2 to -4 and were derived from 2 different data sets. Three studies quoted a data set that has been shown in previous work to be problematic; the only quoted "cutoffs" of -4 were from two of these studies.

CONCLUSIONS: Surprisingly few (26.3%) studies mention what pulmonary annulus size "cutoff" was used to decide when to insert a TAP. Z-scores derived from different populations were used by different studies and it is possible that this may have contributed to the varied "cutoffs' quoted. Recommendations to perform valve-sparing surgery in pulmonary annuli as small as -4 may not be warranted. Future papers should record "cutoffs" employing recommended z-score data set.