NPPB and sleep apnea syndrome: On the contrary, although no step-by-subgroup interactions were found between the variation of the fSVI and the subgroups of age, BMI, AF, type of predominant SDB, BNP, baseline RVSP, baseline LVEDV index, and baseline MR degree, significant differences were found in the variations of fSVI based on sex, baseline LVESV index, and baseline fSVI (P for interaction = 0.006, 0.034, and 0.017, respectively; Figures 3A–C).