Pulmonary Hypertension

Marc Humbert, M.D., Ph.D. Rajan Saggar, M.D.

This issue of Seminars in Respiratory and Critical Care Medicine is dedicated to the topic of pulmonary hypertension (PH). This combined effort by physician-scientist experts from the United States and Europe provides a “state of the art” discussion of a rapidly growing body of literature.

The potential for PH is a common thread in a group of diseases with seemingly variable underlying pathophysiology. Importantly, pulmonary arterial hypertension (PAH), either idiopathic or complicating another disease, unvaryingly imparts a negative prognosis, and as such, regardless of proven available therapies, clinicians must maintain a high index of suspicion. The first four articles discuss the definition and classification, pathology, genetics, and hemodynamic assessment of PAH.

The next several articles highlight the heterogeneity of the diseases that may be complicated by PAH, including idiopathic PAH, pulmonary veno-occlusive disease, congenital heart disease, connective tissue disease, HIV infection, liver disease, schistosomiasis, and hemoglobinopathies. Interestingly, the incidence/prevalence, prognosis, and response to available therapies in these variable settings of PAH also lack uniformity and predictability. One example highlighting this discrepancy may be pulmonary veno-occlusive disease, wherein one patient overtly decompensates with initiation of vasodilator therapy, while another may have undeniable, objective long-term benefits.

PH can also develop in the setting of parenchymal lung disease, a myriad of both obstructive and restrictive lung diseases. Work is ongoing to define which therapies, if any, may be beneficial in this unfortunate “double-hit” population. The next article discusses chronic thromboembolic disease, a more fortunate PH population, given a surgical therapeutic option with very acceptable long-term outcomes.

The final articles are dedicated to available therapies for PAH, and although existing options appear to improve morbidity and survival, the only cure for PAH remains lung transplantation. The limitations of the current lung allocation scoring system, the existing medical therapeutic options, and the relatively younger age of these patients can, however, still cloud the optimal timing for referral and active listing for lung transplantation.

In summary, this issue provides an outstanding overview of the existing PH literature by several experts in the field. An exciting foundation has been established on which to build bench, clinical, and translational research platforms to further define and understand this disease process. In addition, PH clearly extends across several specialties and lends itself to the potential for combined future research initiatives.