How frequently and how soon after starting a patient on flecainide should they undergo exercise treadmill testing to look for QRS widening due to use-dependence?

This concept has been around, but in my training and experience is mostly theoretical. This has been looked at in a small study and found to be very rare (Vallurupalli et al., PMID 26100588).

It is not located in the guidelines for AF management (it is only briefly mentioned in the 2011 guidelines).

T...

Following initiation of flecainide or after a dose escalation, exercise treadmill testing is typically performed once, early in therapy, generally within 1–2 weeks, after steady-state drug levels are achieved. The purpose is to evaluate for rate-dependent QRS widening related to use-dependent sodium...