A critical appraisal of the updated 2014 Nice Pulmonary Hypertension Classification System

In 2013, the Fifth World Symposium on Pulmonary Hypertension (PH) was held in Nice, France. This meeting has been held every 5 years since the Second World Symposium in 1998, when the modern-day classification system of PH was initially conceived. PH is a pathophysiologic state of the pulmonary circulation characterized by an increased mean pulmonary artery pressure ≥ 25 mm Hg at rest, and can be the consequence of a variety of distinct disease entities. The rationale of a classification system for PH was to group together disease entities that share similar pathomechanisms, clinical presentation, and therapeutic approaches. Refinements of the classification system have been made at each subsequent World Symposium, reflecting the ongoing research and new knowledge acquired in the science of PH. We provide an update of the recent changes made to the PH classification system from the Nice meeting.