Fig. 4

a, b Relationship between lower TK orientation and CS ostium direction. a Scatter plot of the association between changes in lower TK orientation (ANGlower) and CS ostium direction (ANGcs). Linear regression analysis demonstrated a significant correlation between TK orientation and CS ostium direction. Dashed lines indicated 95% confidence interval. Pearson’s correlation coefficient r = 0.86 (P < 0.001), and R2 = 0.732. TK = triangle of Koch; CS = coronary sinus. b The relationship between the difference between ANGCS and ANGlower (ANGlower-ANGCS) and the average of ANGCS and ANGlower by Bland-Altman analysis. The data reveals that ANGlower-ANGCS was 5.54 ± 0.48° with the 95% confidence limits spanning from − 4.23° to 15.18° (upper and lower dotted lines)