Comparison of plasma NT proBNP in studied groups. Boxes show median and interquartile ranges (IQR) between the 25th and the 75th percentiles. The horizontal line inside the box represents the median, and I bars (lines) represent the highest and lowest values (range of concentrations). The small closed squares represent extreme values (more than 3 IQR), and small open circles represent the outlier values (between 1.5 and 3 IQR).