Received: 13 July 2019
Revised: 4 December 2019
Accepted: 18 December 2019
First Online: 2 January 2020
Compliance with ethical standards
: MM reports honoraria from Siemens HealthCare and Edwards Lifescience outside the submitted work, and YZ reports lecture fees from Baxter, MSD and Shire outside the submitted work. The other authors declare that they have no conflict of interest.