Figure 1. Current PH classification system.

Patients with pulmonary hypertension (PH) in association with connective tissue disease may sit in group 1 (pulmonary arterial hypertension), group 2 (PH associated with left heart disease) or group 3 (PH associated with lung disease) while group 4 (chronic thromboembolic pulmonary hypertension) disease must also be excluded. Reproduced with permission [77]