This study is talking about two groups, one with a target INR of 2.0-2.5 and the other with a target INR of 2.5-3.5. The higher dose is the current standard dose.
The outcomes were extremely close group to group and it looks like the Confidence Interval was greater than 1.5%, so the study was not adequately powered to have confidence of non inferiority. Is that interpretation correct? Obviously the difference in the groups was not large, but it reads to me that they couldn’t be sure it was close enough to not be worse with the lower dose, therefore they can’t eliminate the possibility that low dose treatment is more dangerous than current dose? If so, would they do another study or would that basically amount to p-hacking? Further thoughts are appreciated.
The link to the follow up study seems to be split, but I was able to pick together the link There are two major differences between the two studies: 1. The first one looked at mitral valves, and this one studied aortic valves; 2. The target INRs were different, although given the difference between aortic and mitral valves, both correspond to an INR 0.5 points lower than standard targets.
In your case, given the risks involved, a mechanical valve sounds like the best choice. I mostly see valve replacements in the elderly, so there’s my personal observational bias. I’m from the US. From what I can tell about our warfarin recommendations, On-X aortic valves do get warfarin and aspirin at lower INR targets. In contrast, there is no such recommendation for On-X valves in the mitral position (yet).