European Journal of Cardio-Thoracic Surgery 0 (2018) 1 LETTER TO THE EDITOR RESPONSE echocardiography as a matching element in the propensity score matching. In the propensity score matching, we ended up using only 58% of the patients after we tried a 1:1 ratio data set using the nearest neighbours method, hoping to re- a b a, Hyungtae Kim , Junhee Han and Si Chan Sung * produce the data as similar as possible to randomized controlled trial data. Department of Thoracic and Cardiovascular Surgery, Pusan National During calibration of various parameters, merely 25 of 43 patients were University Yangsan Hospital, Yangsan, Korea matched. It is possible to reduce the calibration conditions later or to sample at Department of Statistics, Hallym University, Chuncheon, Korea a 1:2 ratio in the future. Received 4 April 2018; accepted 6 April 2018 REFERENCES Keywords: Tetralogy of Fallot � Pulmonary valve regurgitation � Biostatistics  Romeo JLR, Papageorgiou G, Takkenberg JJM, Mokhles MM. Time de- We read the Letter to the Editor by Romeo et al.  regarding our recently pub- pendent right statistics: this is the moment. Eur J Cardiothorac Surg lished article . The pulmonary regurgitation (PR) grade is usually divided into none, mild, moderate and severe. In our article, we added a category and divided  Kim H, Sung SC, Choi KH, Lee HD, Kim G, Ko H et al. Long-term results PR grade into none (0), trivial (0.5), mild (1), moderate (2) and severe (3) . With of pulmonary valve annular enlargement with valve repair in tetralogy of respect to these PR grades, as each numerical value does not have quantitative in- Fallot. Eur J Cardiothorac Surg 2018; doi:10.1093/ejcts/ezx497. formation, we believe that it is problematic to compare it as a continuous vari-  Ito H, Ota N, Murata M, Tosaka Y, Ide Y, Tachi M et al. Technical modiﬁ- able. Other tests, such as cardiac magnetic resonance, are usually performed to cation enabling pulmonary valve-sparing repair of a severely hypoplastic quantitatively measure the degree of PR and make a comparison. Unfortunately, pulmonary annulus in patients with tetralogy of Fallot. Interact we did not have access to these quantitative data, and inevitably, comparisons CardioVasc Thorac Surg 2013;16:802–7. were made using the last PR grade as a continuous variable. Moreover, propen- sity score matching showed that the incidence of patients with moderate or higher PR was lower in ourpulmonary valverepairtechnique. *Corresponding author. Department of Thoracic and Cardiovascular Surgery, Another point is that the development of PR increases with time following Pusan National University Yangsan Hospital, Mulgeum-eup, Yangsan-si, surgery. When comparing patients, it is not ideal to make comparisons without Gyeongsangnam-do 50612, Korea. Tel: +82-55-3602127; fax: +82-55-3602157; considering this variable. However, the PR data of our patients were not linear e-mail: firstname.lastname@example.org (S.C. Sung). over time, but rather the PR value seen on the last echocardiography. To over- come this problem to some degree, we considered the follow-up period for the doi:10.1093/ejcts/ezy185 The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. Downloaded from https://academic.oup.com/ejcts/advance-article-abstract/doi/10.1093/ejcts/ezy185/4991912 by Ed 'DeepDyve' Gillespie user on 12 July 2018 LETTER TO THE EDITOR
European Journal of Cardio-Thoracic Surgery – Oxford University Press
Published: May 2, 2018
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