Although higher FC at diagnosis was significantly associated with greater days of ICU hospitalization per year of life (FC IV 138 ± 146 days vs. FC I 12 ± 19 days, p = 0.0001), it was not significantly associated with hemodynamic parameters at time of diagnostic right heart catheterization, occurrence of cardiac arrest or syncope, treatment with prostacyclin derivatives, ERAs, or PDE5 inhibitors, total lifetime number of PH therapies, or highest recorded BNP level (data not shown). This evidence concerns the gene PDE5A and cardiac arrest.