So, an update. My surgeon has installed 1000s of St Jude valves over 20+ years. She thinks an On-x is a good choice for me and will install it. Problem is she has not installed an ON-X before but claims the procedure is exactly the same as a St Jude. Is this true? I am now leaning toward just going with the more tested St Jude. Is there a practical difference between an INR of 2.5 and 1.8 anyway?