Pulmonary Arterial Hypertension (PAH)

Pulmonary hypertension (PH), which is associated with a diverse range of diseases, is characterized by a marked increase in pulmonary vascular resistance. Patients frequently describe nonspecific symptoms, such as worsening weakness and dyspnea on exertion. The course is progressive, and symptom management as well as treatment of underlying disorders is required.1 Individuals with PH have a resting mean pulmonary arterial pressure (mPAP) of 25 mm Hg or higher on right ventricular cardiac catheterization. Group 1 of PH, in the classification of the World Health Organization, is pulmonary arterial hypertension (PAH), which is characterized by a mPAP of 25 mm Hg or higher, a pulmonary arterial wedge pressure of 15 mm Hg or lower, and pulmonary vascular resistance of more than 3 Wood units. PAH is subdivided according to etiology; idiopathic PAH accounts for the majority of cases, followed by PAH secondary to connective tissue disease, PAH secondary to congenital heart disease, toxin-induced PAH, and PAH related to other ailments.2,3 

Clinical Features of PAH 

In PAH, pathological vascular remodeling leads to increased pulmonary arterial pressures and ultimately dysfunction of the right ventricle.4 Dyspnea, tiredness, chest pain, lightheadedness, syncope, and edema of the lower extremities are some of the first symptoms. In most cases, the diagnosis is delayed by an average of 2 years because the symptoms are nonspecific.5 

Progressive dyspnea during exercise, often accompanied by fatigue, is the hallmark symptom of all forms of PH. The symptoms worsen as the disease progresses and new ones emerge, such as dyspnea while bending forward (bendopnea). Syncope generally occurs either during or soon after physical activity. Frequent episodes of syncope, even with light effort, in an individual with PH indicates the presence of a life-threatening condition. The right cardiac filling pressures rise during cardiac decompensation, resulting in the classic triad of cervical venous congestion, ascites, and edema.6

Patients with compensated PH frequently have no physical abnormalities. Peripheral or central cyanosis (typically brought on or exacerbated by exercise), a prominent pulmonary valve component of the second heart sound, and a systolic flow murmur reaching a maximum at a left parasternal site in tricuspid valve insufficiency are the most common and often subtle signs. Cardiac findings therefore include a loud pulmonary component of the second heart sound (93%), a pansystolic murmur of tricuspid regurgitation (40%), and a diastolic murmur of pulmonary insufficiency (13%).5,6 Changes in right ventricular function and structure are reflected in the physical signs of PH. Jugular vein distention, hepatomegaly, edema, and ascites are some of the extracardiac signs. Lung examination findings are generally unremarkable.

Dyspnea in a patient without overt signs of a specific heart or lung disease should raise the clinical suspicion of PH. If dyspnea or other symptoms associated with right ventricular dysfunction develop in a patient with underlying heart or lung disease, or with a disease often associated with PAH (eg, connective tissue disease, liver cirrhosis, congenital heart disease, human immunodeficiency viruses [HIV] infection), the patient should be evaluated for PAH.7

The natural course of PAH is characterized by progression to right-sided heart failure, which is usually noted to some degree at the time of diagnosis. Other causes of death in PAH, apart from right-sided heart failure, include complications of pulmonary artery dilatation. Pulmonary artery dissection and rupture, severe hemoptysis, and left main compression syndrome, in which the trunk of the pulmonary artery compresses the left main coronary artery, are among the complications of PAH. Because hypoxic vasoconstriction in the pulmonary arteries leads to collateralization and proliferation of the bronchial arteries, hemoptysis is frequently secondary to a bronchial arterial source. Supraventricular and, less frequently, ventricular arrhythmias may also arise as a result of right-sided heart illness.8 


  1. McLaughlin VV, Archer SL, Badesch DB, et al. ACCF/AHA 2009 expert consensus document on pulmonary hypertension a report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents and the American Heart Association developed in collaboration with the American College of Chest Physicians; American Thoracic Society, Inc.; and the Pulmonary Hypertension Association. J Am Coll Cardiol. 2009;53(17):1573-1619. doi:10.1016/j.jacc.2009.01.004
  2. Oldroyd SH, Bhardwaj A. Pulmonary hypertension. StatPearls [Internet]. Updated August 11, 2021. Accessed March 16, 2022.
  3. Lan NSH, Massam BD, Kulkarni SS, Lang CC. Pulmonary arterial hypertension: pathophysiology and treatment. Diseases. 2018;6(2):38. doi:10.3390/diseases6020038
  4. Prins KW, Thenappan T. World Health Organization group I pulmonary hypertension: epidemiology and pathophysiology. Cardiol Clin. 2016;34(3):363-374. doi:10.1016/j.ccl.2016.04.001
  5. Krowl L, Anjum F, Kaul P. Pulmonary idiopathic hypertension. StatPearls [Internet]. Updated December 8, 2021. Accessed March 16, 2022.
  6. Hoeper MM, Ghofrani HA, Grünig E, Klose H, Olschewski H, Rosenkranz S. Pulmonary hypertension. Dtsch Arztebl Int. 2017;114(5):73-84. doi:10.3238/arztebl.2017.0073
  7. Jawad A, Heresi GA, Tonelli AR, Dweik RA, Chaisson N. Pulmonary arterial hypertension. Cleveland Clinic Center for Continuing Education. Published August 2017. Accessed March 16, 2022.
  8. Schwab KE. Pulmonary arterial hypertension clinical presentation. Medscape. Updated August 6, 2021. Accessed March 16, 2022.

Reviewed by Kyle Habet, MD, on 3/31/2022.