I'm probably interpolating things I'd been told into what was generally know or which could be spoken of with impunity 
so who knows any more what the real situation was. I only know we didn't see the 'real KS' in the Gold Cup - and said so at the time (vociferously and more than once LOL). I also got a number of emails following up various conversations (I was in Lambourn for all that Cheltenham btw) giving me 'further and better particulars' in strictest confidence.
I'm very much in the Betsmate camp here - another KS nutter; and like him all I'd really love to see is a totally fit and 'up for it' KS and Deman going head to head - but I doubt we ever shall now. A great sadness
Anyway - about Denman and his heart. Just to show that I'm not talking complete bollocks, I've found a few articles on Equine Atrial Fibrillation which make the various kinds of AF and their treatment - and its possible outcomes and consequences - a bit clearer.
Atrial Fibrillation in equines:
http://www.tceh.co.uk/news.htm
Some technical stuff on the various types of AF:
http://www.tufts.edu/vet/sports/cardiac.html
Power-point presentation regarding heart problems in horses.
rover.vetmed.lsu.edu/student/2009/Equine%20CardiologyI.ppt
In case you can't open it (needs powerpoint), it makes three things clear:
1) Recurrence is more likely in some cases than others, but can NEVER be ruled out even in cases with a 95% prognosis for full recovery
2) Testing for actual recurrence is problematical, since almost all horses with an intermittent AF problem will only manifest symptoms when under maximum (or near-max) pressure at excercise. So you can't really tell how successful the treatment has been until you put the horse to the acid test of being under racing pressure again
3) The drug of choice, and with which Denman was treated, is Quindine. It can only be employed three times and it's pretty toxic; one inevitable consequence is severe loss of condition. Another of its common side-effects in horses is *depression*
Horse & Hound forum - some interesting posts with varied experience:
http://www.horseandhound.co.uk/forums/showflat.php/Cat/0/Number/3891388/Main/3880604/
Trainer Magazine has an article on the equine heart in the December issue, but it's not all available online for free (I'll be able to read it at the weekend I hope). It has toher articles on AF as well btw
http://www.trainermagazine.com/europe/index.php?mact=News,cntnt01,detail,0&cntnt01articleid=98&cntnt01origid=15&cntnt01returnid=27
