Conclusions and study implications
The findings of the present study indicate that the short-term increase in NTproBNP levels after AF onset—which according to previous observations lasts for 24–48 h even in patients remaining in AF—may be used to assess the age of the arrhythmia in patients with AF of unknown onset. This conclusion is supported by the finding that raised NTproBNP levels, presumably indicative of recent-onset AF, were indeed associated with less thrombotic burden on TEE and thus, by extrapolation, with lower thromboembolic risk.