Text and Data Mining valid from 2020-02-03
Received: 8 June 2019
Accepted: 24 January 2020
First Online: 3 February 2020
Ethics approval and consent to participate
: The present study was approved by the ethics committee of the Fuwai Hospital.
: All authors have participated in the work and have reviewed and agreed with the article content.
: The authors declare that they have no competing interests.