Bob sites a paper above that argues that re-operation is safer than initial operation and further argues that therefore people should choose tissue valves.
http://www.pccvs.com/files/documents/articles/redoavrarticle.pdf
Unfortunately this paper is just another example of the worst form of "research" in the medical literature. The flaws include:
Retrospective design: That means there was not a structured trial to examine if there really was a difference. The study was not planned and then executed so that confounding factors could be controlled. It was executed then an analysis was made to try to somehow deal with confounding factors that definitely did occur. Now, retrospective analysis can be acceptable if there is rigorous attention to other details, but there wasn't any such attention as I enumerate below.
No patient selection criteria: They took all comers and eliminated no one. This made the spread of risk factors huge and unbalanced, some favoring the initial group, some favoring the re-op groups. There was no attempt to match the groups for risk factors. This makes for a complete mess. They tried to do a multivariate analysis but I think that was inadequate considering the mess they started with.
Temporal Effects were not controlled: There was no information about when the operations were done. The reops may have benefited from advances in surgical technique, changes in hospital practices and improvements in supportive care. Yes, things usually get better with time. So, that should favor initial as well as reops, if they were done at the same time.
The results were not statistically significant: In other words, they could not show that the difference between 4.1 % and 3.1% was any thing other than chance. The P value was 0.89. That means there was an 11% chance that this difference is "real". Now, that, in fact, is not the right way to interpret P values, but it is sufficient to say they did not find a difference. A repeat of this at another institution would just as likely show opposite results.
There are many other flaws, but this study is essentially useless.
Now, this doesn't mean that the basic premise of the paper is not true, or that op + reop is not more dangerous than op + coag, but this paper does almost nothing in my mind to support that claim. I think that these questions have more complex answers.
My basic position is that most of us here are not in a position to evaluate the medical literature and draw our own conclusions. Even with my years of training and experience doing so, I am reluctant to suggest others do this. Those who suggest you can gather a bit of "information" here and direct your own care need to reconsider this. Some of what I have read as information here is flat wrong. For example, the notion that exercise increases warfarin metabolism was floated as fact, and the reference cited for this was an early post made here. That is called circular referencing. There is no evidence at all and considerable reason to expect this is not true from basic information about how warfarin is absorbed and metabolized. Ask the medical staff managing your warfarin therapy.
So, read all you want here, then run the information by the health professionals you expect to provide your care and rely on their feedback. I spent more than a month trying to come to my own conclusion about how my AVR should be done, and I had many conversations about information I read here with my surgeon and his team. I never made my own conclusions without the concurrence of the surgical team, and I was very concerned that anything I read here or elsewhere that was counter to their thinking was given a thorough airing with them.
