“…Our results do apply to the subgroup of patients with out-of-the-box settings with fixed AV and VV delays; also, our results apply to a population of patients treated in the period 2013-2018 and it is possible that response to CRT in contemporary practice may be better thanks to the progressive use of quadripolar leads and AV optimization algorithms. We analyzed the occurrence of AF > 7 days as a function of PR interval, even if many factors may actually condition AF onset in patients with LV dysfunction and AF [2,27,[31][32][33][34][35]. Additionally, given the observational nature of the study, granular descriptions of specific echocardiographic measurements, such as grade and type of valvular heart disease, were missing.…”