Letter by Charitos et al regarding article, "Reoperation of left heart valve bioprostheses according to age at implantation".

Letter by Charitos et al Regarding Article, “Reoperation of Left Heart Valve Bioprostheses According to Age at Implantation” To the Editor: We read with great interest the work of Chan and colleagues1 on the age-stratified incidence of reoperations after left heart biological valve implantation. Results on this area of research were greatly anticipated because previous works in this field were sparse and often plagued by small patient populations or older valve prostheses that are now off the market. We have some concerns, however, about the graphical representation of freedom from reoperation as a continuous function of patient age at the time of operation (Figure 2).1 There seems to be a discrepancy between the actuarial freedom from reoperation estimates in Figure 1A and the age-stratified estimates in Figure 2A. If Figure 2 presents actuarial estimates, the authors should provide more information on how these estimates were obtained. If Figure 2 represents predictions of a Cox proportional hazards model, the estimates for freedom from reoperation in young patients based on a model averaging risk factors from a population heavily skewed toward older patients may provide dysfunctional estimates. The authors should explain the discrepancy between Figures 1 and 2 in the young patients, because this bears the potential of misinterpretation both from clinicians and patients. We believe that the data presented in this work will facilitate decision making when informing patients before heart valve replacement, and we congratulate the authors for undertaking this project.