It has become increasingly clear in the last two decades, thanks to epidemiological studies and clinical trials, that Group 3 pulmonary hypertension is in fact a constellation of different and varied phenotypes.

Reports documenting the presence and impact of pulmonary hypertension (PH) complicating lung disease date back to the early 1980s. Ever since effective therapies for group 1 pulmonary arterial hypertension started to emerge in the 1990s with IV epoprostenol, through the early 2000s with the endothelin receptor antagonists and PDE-5 inhibitors, there has been increasing interest in the potential role of these therapies for PH beyond group 1 disease (1)...