Statistical analysis
The patients were divided into two groups: group A included patients whose NTproBNP levels exceeded the respective cut-off value in any of the three samples while group B included the rest of the patients with NTproBNP levels below the cut-off value. The required sample size was 42 per group, calculated beforehand with the assumption of 25 percentage points of difference in the occurrence of LA/LAA thrombi between the two groups (group A with presumably recent-onset AF and group B with presumably older AF), at an α level of 0.05 to achieve statistical power of 80%. Continuous variables were expressed as mean±SE of the mean and compared using the Student t test. Categorical variables were expressed as counts or percentages and were compared using the χ2 test or the Fisher exact test if the produced matrices contained cells with expected values