I do not know a gold standard. However, we were using ilomedin (iloprost) intravenously in increasing concentration during right heart cath to assess a response on TPG/PVR before listing patients for cardiac transplantation. If they respond well and TPG decreases during iloprost infusion the patient could be listed. Yet, I know from other centres who treat patients with bosentan p.o. for 6 month before they are re-evaluated for heart transplantation