Editorial Comment: Repair of tetralogy of Fallot: the right ventricle and the two villains

In this issue of the Journal, Awori et al. [1] propose the criteria for valve-sparing repair of tetralogy of Fallot, with emphasis on the lowest acceptable pulmonary annulus size. It is well known, in practice, that repair of tetralogy of Fallot almost never yields a functional arrangement as good as normal. Even an ‘optimal’ repair is eventually unsettled by competing failure mechanisms acting more or less independently on the target cardiac chamber, the right ventricle. Due to the anatomical constraints imposed by an hypoplastic pulmonary annulus, the determinants under consideration, i.e. residual right ventricular pressure and/ or volume overload (the two villains), are most often only partially tackled at repair and are in fact deliberately maintained in a sort of antagonistic balance. Ideally, repair of tetralogy of Fallot should incorporate a normal-sized and well functioning pulmonary valve. And everybody would concur with Dr Geva’s auspice for the development of a bioengineered pulmonary valve substitute, as well as of a contracting right ventricular outflow patch with biomechanical properties of the myocardium [2]. While awaiting research advances, pulmonary outflow reconstruction, as part of repair of tetralogy of Fallot, may only seek the best compromise between residual pressure and volume overload. Depending on the individual anatomy of the right ventricular outflow tract, ‘well balanced’ valve-sparing repairs conceivably provide the best approximation of this principle. The main issue is: how tight of a residual pulmonary stenosis is acceptable in the pursuit of minimal or no residual pulmonary regurgitation? Awori et al .[ 1], with an elegant study on 46 patients undergoing valve-sparing repair of tetralogy of Fallot, identify the minimum acceptable pulmonary valve annulus as the one with a z-score equal to or greater than �1.3. Smaller z-scores determined residual outflow pressure gradients above the acceptable threshold level of 30 mmHg. In the face of a sophisticated analysis, though, the dataset reviewed is quite small and presents some degree of inconsistency. In fact, only four patients (9% of the series) qualified for a z-score just below �1.3 and five patients with a greater z-score (�0.5 to �1.0) had a residual gradient >30 mmHg. These limitations somehow debilitate the rec