What I get from this is that the AF must be a current, ongoing, and possibly co-adjunct disorder or disease with at least valve disease and/or atherosclerosis. So, the cited reference says more must be done in the way of research to establish the relationship.

To me, the risk of all kinds of subsequent disorders and conditions falls when the AF is controlled, either by drugs or by catheter ablation. What people should take from this is that, once you have AF, it's likely to progress, but it's also likely to bring on other undesired conditions. If you'd like to minimize your personal risks of such evolution, seek medical intervention EARLY! AF is more intractable the more it is left untreated. Get medical intervention before it progresses to more advanced forms and before it compromises the rest of the heart.