*Limitations*

The number of patients in our study was small. We were not able to track patients for a long period of time, particularly those who were referred from external facilities, because this was a retrospective study. This study included data from over approximately 15 years. During this period, the development of disease-modifying treatments was improved, which may have altered study outcomes. The small number of patients with genetic variants also has a limitation regarding the significance of the association with variants and prognosis. To clarify the effect of variants on clinical manifestations and prognosis, further analyses of larger numbers of patients are required. Additionally, functional analyses are also required to clarify the significance of the identified variants which contribute to the etiology of LVNC.

#### **5. Conclusions**

To the best of our knowledge, this is the first large cohort study to reveal the etiology and genetic background of LVNC and CHD. Recognition of the association between LVNC and CHD is crucial considering the increased risk of CHF as demonstrated in our results. Moreover, our data suggest that concomitant LVNC with CHD is a surgical risk factor, so additional perioperative planning such as CHF treatment may be beneficial if identified preoperatively. Therefore, elucidation of genotype-phenotype correlation in patients with LVNC and CHD may be important to understand the pathophysiology and development of LVNC in patients with CHD. Further studies will continue to determine long-term and genotype–phenotype correlations.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2077-0383/9/3/785/s1, Table S1: List of 182 analyzed genes of NGS, Table S2: Silico predictive algorithms used in the study, Table S3: List of patients with extracardiac anomaly, and Table S4: Gene collapsing test of rare variants.

**Author Contributions:** Conceptualization, K.H.; methodology, Y.H.; validation, N.N. and N.Y.; formal analysis, Y.H; investigation, S.T. and H.N. and K.I. and S.O.; data curation, M.O.; writing—original draft preparation, K.H.; writing—review and editing, K.H.; visualization, N.M.; supervision, F.I.; project administration, K.H.; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors wish to acknowledge Masaya Aoki, Teruhiko Higashida, Daisuke Torizuka, Hitoshi Moriuchi, Haruna Hirai, and Eriko Masuda for their expert technical assistance.

**Conflicts of Interest:** The authors declare no conflict of interest.
