Chronic post-embolic pulmonary hypertension: a new target for medical therapies?

The rationale for the use of pulmonary arterial hypertension-targeted drugs in chronic thromboembolic pulmonary hypertension is based on four bundles of evidence, as follows: 1) the pathobiology of the disease, with a distal component of pre-capillary arteriopathy that is very similar to pulmonary arterial hypertension; 2) the inoperability of some patients, and the persistence or recurrence of pulmonary hypertension after pulmonary endarterectomy in others; 3) the short-term efficacy and safety of pulmonary arterial hypertension-targeted drugs in these patients; and 4) their potential effect on survival. Chronic thromboembolic pulmonary hypertension is essentially a surgical disease, curable by pulmonary endarterectomy, with acceptable procedural mortality in experienced centres. Patient selection for surgery is extremely complex and results in 30-50% of patients considered inoperable. A large clinical experience has been built up with endothelin receptor antagonists and phosphodiesterase-5 inhibitors, while evidence from controlled trials is running far behind schedule. More recently, a randomised controlled trial with the guanylate cyclase stimulator, riociguat, achieved its target and showed haemodynamic, as well as functional, improvements within 4 months of therapy. The place of this therapy in the therapeutic arsenal needs to be further defined, but should be strictly limited to inoperable patients.