An official website of the United States government
Here's how you know
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Event-free probability curves comparing time to event in Open vs. Closed groups using median time of fenestration closure as time zero for calculating event intervals (see text for explanation).