To the Editor,

We thank Thomas Krasemann for his interest in our article published by Schran(t)z al. regarding the experience with the “Hybrid Approach” for treatment of patients with hypoplastic left heart (HLH) and its variants [3]. We fully agree with Krasemann’s remarks. The Aristotle score system was originally developed as a complexity score for surgical procedures for congenital heart disease, and divides into a procedure-dependent basic score and a comprehensive Aristotle score [1]. We didn’t assume that the complexity of the hybrid stage I approach is similar as Norwood stage I procedure, because one of the advantages of the hybrid procedure is its technical simplicity. Therefore, the Hybrid approach is not only a procedure for elective patients with HLH, but more importantly an effective treatment for high-risk cases. The Aristotle score was not changed by simply subtracting the calculated score number by 14.5 (surgical) points as published by Lloyd et al. [2] because we believe that the readers of the Pediatric Cardiology might be able to do this mathematical calculation, if they want to. The Aristotle score of 19 is well known as a cut-off value considering a high-risk candidate for a Norwood operation, but score number of 4.5 is not. Therefore, we prudently used the Aristotle score assessing the complexity of our hybrid patient population in terms to compare the preoperative risk factors, as if a Norwood operation would have been considered for the first stage. Calculating preoperative risk factors for an established surgical approach like a Norwood operation, but with the consequence to avoid such risky procedure by a less invasive alternative could be summarized as progress.