Physio and Physio II rings: beyond the annular physiology.

Background: Engineering of the Carpentier-Edwards Physio (PR-I) and Physio II (PR-II) rings (Edwards Lifesciences Corp., Irvine, CA, USA) combines flexibility with remodeling. PR-II is considered an improvement of PR-I, as it boasts of an improved shape, a double saddle, and a sewing cuff that reduces tension on sutures.