Received: 12 July 2019
Accepted: 19 December 2019
First Online: 10 January 2020
Ethics approval and consent to participate
: Ethical approval was obtained from Beijing Anzhen Hospital ethics committee (No. 2018011X). This retrospective study was conducted without informed consent for some objective reasons and was approved by the ethics committee. The protocols of our study obeyed the principles of the 1983 Declaration of Helsinki. The data used in this study was anonymous before its use.
: Not applicable.
: The authors declare that they have no competing interests.