Evolution of the Z-score in size-reduced bicuspid homografts

Human homografts are frequently used to establish an anatomic continuity between the right ventricular outflow tract (RVOT) and the pulmonary artery. Their limited availability, especially in small sizes, has encouraged the use of alternative strategies, such as size-reduced bicuspid homografts. The study aim was to analyze the follow up of patients who had received a standard tricuspid or size-reduced bicuspid homograft in the RVOT position, and to investigate modifications of the patients' Z-scores over the years.

A consecutive series of 107 patients aged < or = 16 years, who underwent RVOT repair between 1989 and 2010 to treat tetralogy of Fallot (ToF), was retrospectively reviewed. Of these patients, 17 received a size-reduced bicuspid pulmonary homograft, while 90 received a standard tricuspid homograft. The mean follow up periods were 10.5 years (range: 0.02-21.4 years) for the whole study population, and 11.8 years and 3.4 years, respectively, for the tricuspid and size-reduced bicuspid homograft groups.

Freedom from mortality at 10 years was 95 +/- 3%. During the observation period, 27 patients (31%) in the tricuspid homograft group and two (125) in the size-reduced bicuspid group presented with graft failure. According to the multivariable analysis, the only independent predictor of graft failure was patient age (hazards ratio 0.86). The 17 patients who had received a size-reduced bicuspid homograft were then age-matched to an equal-sized population of tricuspid homograft patients. A comparative analysis of the time-weighted average of the Z-scores for these tricuspid and size-reduced bicuspid homograft subgroups during the follow up period failed to identify any statistical difference (p = 0.5).

In terms of Z-score evolution, size-reduced bicuspid homografts offer results which are comparable to those achieved with tricuspid homografts.