HDAC2 and idiopathic pulmonary arterial hypertension: The mean levels of RVSP with respect to PAI-1 genotypes were (X±SD) 101.90 ± 24.84 for Hd1/Hd1, 100.52 ± 30.79 for Hd1/Hd2, and 102.29 ± 16.23 for Hd2/Hd2, with mean RVSP being higher in the Hd2/Hd2 genotypes, further supporting the Hd2 association with IPAH; and the association can be correlated to the severity of the disease, increased mPAP pressures, and Tricuspid regurgitation (TR) velocity [Table 4].