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

Awori and colleagues reviewed 19 published studies on repair of tetralogy of Fallot (TOF), representing 2,500 patients of which 54.8% had a transannular patch (TAP) inserted to relieve right ventricular outflow tract obstruction. The measured pulmonary annulus size, expressed as a z-score, is often used to determine when to insert a TAP, however similar z-scores derived via different methods can represent different annulus sizes and flow rates. Multiple suggested z-score “cut-offs” are quoted in the literature, and the authors wanted to know whether differences in z-score calculation methods were related to these different cut-off values. Surprisingly few studies (26.3%) mention what pulmonary annulus size “cut-off” was used, but the authors conclude that derivation of z-scores from different data sets may contribute to different cut-off values.