The following are excerpts from Resource (1) below:
Pulmonary hypertension is a common, complex group of disorders that result from different pathophysiologic mechanisms but are all defined by a mean pulmonary arterial pressure of 25 mm Hg or greater. Patients often initially present to family physicians; however, because the symptoms are typically nonspecific or easily attributable to comorbid conditions, diagnosis can be challenging and requires a stepwise evaluation.
(2) Echocardiography in Pulmonary Arterial Hypertension: from Diagnosis to Prognosis [PubMed Abstract] [Full Text HTML] [Full Text PDF]. J Am Soc Echocardiogr. 2013 Jan;26(1):1-14. doi: 10.1016/j.echo.2012.10.009. Epub 2012 Nov 8.