Negative logarithmic relationships between IL-6 and RV function and RV-PA coupling in PAH. Negative logarithmic relationships between IL-6 and RVFAC (r = −0.67) (A), TAPSE (r = 0.61) (B), RV-PA coupling Model 1 (RVFAC/mPAP) (r = −0.53) (C) and RV-PA coupling Model 2 (TAPSE/mPAP) (r = −0.48) (D) exist in PAH patients. The natural logarithmic transformation of IL-6 is significantly associated with RVFAC (r = −0.64, p < 0.0001), TAPSE (r = −0.55, p = 0.0002), RVFAC/mPAP (r = −0.50, p = 0.001) and TAPSE/mPAP (r = −0.44, p = 0.005).