[malaya_zemlya]

My guess, they delay risky procedures until senior doctors get back from the conference

[MattRix]

This is not it, they were measuring 30-day mortality, not just mortality during the exact days of the conference.

[JamisonM]

Even with 30-day mortality this can be the case, heart patients I am sure do survive risky procedures and die two weeks later because of complications due to the procedure fairly regularly. (Not that I have an opinion on the root cause here.)