Pulmonary Arterial Hypertension

Aka: Pulmonary Arterial Hypertension, Primary Pulmonary Hypertension, Pulmonary Hypertensive Crisis, Idiopathic Pulmonary Arterial Hypertension, Familial Pulmonary Arterial Hypertension

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II. Epidemiology

  1. Incidence: 1-2 cases per 1 million (rare)
  2. Female predominance after Puberty in ratio of 1.7 to 1
  3. Most prevalent in ages 20 to 40 years old

III. Causes

  1. See Pulmonary Arterial Hypertension Causes
  2. Idiopathic or familial
  3. Genetic associations
    1. BMPR2 gene
    2. ALK1 gene
    3. Endoglin (with or without Hereditary Hemorrhagic Telangiectasia)

IV. Associated Conditions

  1. Collagen Vascular Disease (e.g.` Systemic Sclerosis)
  2. HIV Infection
  3. Includes Persistent Pulmonary Hypertension of the Newborn
  4. Predisposing medication use (see Pulmonary Arterial Hypertension Causes)

V. Pathophysiology

  1. Progressive narrowing of distal pulmonary arteries and arterioles
  2. Processes
    1. Inflammation
    2. Hypercoagulability
    3. Pre-capillary pulmonary arteriole disorder
      1. Endothelial dysfunction with remodeling and hyperplasia
      2. Excess cell proliferation and dysfunctional apoptosis
      3. Vasoconstriction with increased pulmonary vascular resistance
  3. Mediators
    1. Nitric oxide
    2. Prostacyclin
      1. Reduces Platelet aggregation and causes vasodilation
      2. Reduced in PAH
    3. Cyclic guanosine monophosphate (cGMP)
      1. Vasodilator
      2. cGMP is rapidly degraded by PDE5 (Phosphodiesterase 5) which present in right ventricle of PAH patients
    4. Endothelin-1
      1. Vasoconstricor and Smooth Muscle mitogen
      2. Increased in PAH
  4. Pulmonary circulation obstruction results from underlying factors
    1. Increased pulmonary vascular resistance
      1. Contrast with the normal low-resistance, high compliance pulmonary circulation
    2. Right Ventricular Afterload
      1. Right ventricle gradually compensates for increasing right Ventricular Afterload increases
      2. Right ventricular increased pressure and volume force interventricular septum to bow into left ventricle
        1. Results in decreased left ventricular filling and ejection fraction
      3. Ultimately compensation fails, resulting in Right Ventricular Failure
      4. Right ventricle is unable to compensate for acute increases to Afterload resulting in PAH Crisis

VI. Symptoms

  1. See Pulmonary Hypertension
  2. Dyspnea (60%)
  3. Fatigue (19%)
  4. Syncope or Presyncope (13%)
  5. Chest Pain
  6. Palpitations

VII. Signs

  1. See Pulmonary Hypertension
  2. Signs of underlying cause (e.g. Portal Hypertension, Connective Tissue Disease)
  3. Signs of right ventricular Heart Failure
    1. Jugular Venous Distention
    2. Hepatomegaly
    3. Ascites
    4. Peripheral Edema
    5. Tricuspid regurgitation murmur

VIII. Diagnosis

  1. See Pulmonary Hypertension
  2. Pulmonary Hypertension testing in general
    1. See Pulmonary Hypertension Diagnosis
    2. Includes CBC, Comprehensive Metabolic Panel, BNP, TSH
    3. Includes Chest XRay and possibly CT Chest, EKG, Echocardiogram
  3. Consider additional testing for specific conditions associated with Pulmonary Arterial Hypertension
    1. See Pulmonary Hypertension Causes
  4. Right Heart Catheterization is required for Pulmonary Arterial Hypertension diagnosis
    1. Diagnosis
      1. Normal pulmonary artery wedge pressure (left atrial pressure)
      2. Increased pulmonary vascular resistance (PVR)
    2. Vasoreactive Testing
      1. Response to pulmonary vasodilators during right heart catheterization
      2. Response to vasodilators is an indication for high dose Calcium Channel Blockers

IX. Management

  1. See Pulmonary Arterial Hypertension Management

X. Complications

  1. See Pulmonary Arterial Hypertension Crisis (PAH Crisis)

XI. Prevention

  1. Avoid predisposing factors (e.g. weight loss drugs)
  2. Avoid pregnancy (mortality risk approaches 50% in some studies)
  3. Vaccinations
    1. Influenza Vaccine
    2. Pneumococcal Vaccine
  4. Advanced Directives: Severe Pulmonary Arterial Hypertension
    1. Advise Do-Not-Resuscitate (very poor outcomes for ROSC)
    2. Discuss end-of-life wishes

XII. Prognosis

  1. Modern treatment five year survival (U.S.): 59%
    1. Gall (2017) J Heart Lung Transplant 36(9): 957-67 [PubMed]
  2. Median survival from diagnosis
    1. Prior medications: 2.8 years
    2. New medications: may exceed 10 years

XIII. References

  1. Meter (2013) Crit Dec Emerg Med 27(5): 2-10
  2. Dunlap (2016) Am Fam Physician 94(6):463-9 [PubMed]
  3. Galie (2009) Eur Heart J 30(20): 2493-537 [PubMed]
  4. Simmonneau (2009) J Am Coll Cardiol 54(1 Suppl): S43-54 [PubMed]

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