Subclinical AF and stroke risk

18 Mar

Healey JS, Connolly SJ, Gold MR, Israel CW, van Gelder IC, Capucci A, et al. Subclinical atrial fibrillation and the risk of stroke. N Engl J Med. 2012 Jan. 12;366(2):120–129. PMID 22236222

Funded by the PPM company and a huge list of conflicts at the end.


  • Part 1 Observational
  • Part 2 RCT
  • >65 with high BP who had just had a PPM placed for block/sinus disease
  • excluded anyone with a hx of AF
  • they recorded what happened on the PPM
  • they defined a subclinical atrial tachy as >190 which seems very fast. It doesn’t seem clear what “subclinical” means
  • first part of study was just observational with an outcome of stroke/embolism
  • In the second part they randomised some to have the anti-tachy pacing turned off and the outcome was whether or not the pacing worked


  • n = 2500
  • 10% had an atrial tachy; they say only 7/2500 had a “clinical” tachy but they don’t say what this means either


  • stroke rate was 4% (only 11 pts mind you) v 1.7% (over 3 years or so). Of course there are potential confounders here that might mean that the atrial tachys aren’t the cause and shouldn’t be treated. They say that the difference was the same after adjustment if you believe you can do that


  • whether pacing was on or not they didn’t find any difference when the randomised them. in fact there was more hospitalisation for CHF in the group assigned to having the on-demand pacing on

They conclude with the line that subclinical atrial tachys are associated with stroke. You could argue with that but it may well be true. The much more useful take home point is that the pacing of subclinical atrial tachys doesn’t seem to matter in terms of clinical outcomes

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