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Pulmonary Hypertension


  1. Pulmonary hypertension elevation of mean pulmonary artery pressure to >25 mm Hg at rest, or >30 mm Hg with exercise.
    WHO has defined PAH to be present when a systolic pulmonary artery pressure is >40 mm Hg, which corresponds to tricuspid regurgitation on a Doppler echo cardiogram of 3-3.5 m/sec.
  2. Pulmonary hypertension is primary or secondary in origin.
    1. Primary pulmonary hypertension (PPH) is Idiopathic Basic abnormality in gene lies in: Bone morphogenic protein receptor II (BMPR II) 
    2. Secondary pulmonary hypertension

Causes and mechanism of secondary PAH


Important Points:


Table: Mechanisms of pulmonary hypertension and examples of corresponding clinical conditions.


Reduction in cross-sectional area of pulmonary arterial bed

  1. Vasoconstriction
    1. Hypoxia from any cause (chronic lung disease, sleep-disordered breathing, etc)
  2. Loss of vessels:
    1. Emphysema
    2. Interstitial lung disease
  3. Obstruction of vessels
    1. Pulmonary embolism (thromboemboli, tumor emboli, etc)
    2. Schistosomiasis
    3. Sickle cell disease (LQ 2012)
  4. Narrowing of vessels
    1. Secondary structural changes due to pulmonary hypertension
  5. Increased pulmonary venous pressure
    1. Constrictive pericarditis
    2. LVF or reduced compliance
    3. Mitral stenosis
  6. Increased pulmonary blood flow:
    1. Congenital left-to-right intracardiac shunts
  7. Increased blood viscosity:
    1. Polycythemia




Passive (Post-capillary)


Abnormality that leads to elevated

pulmonary artery pressure is located in the pulmonary artery or arterioles.

Abnormalities that lead to elevated pulmonary artery pressure are located beyond the pulmonary arteries.

These are caused by diseases that lead to increased pulmonary venous pressure that in turn produces secondary elevation in pulmonary arterial pressure.

Left Atrial (LA) Pressure (PCWP)


Pulmonary artery mean arterial pressure and left Atrial Pressure


> 12mm



Primary pulmonary hypertension

Disorders of ventilation

Congenital heart disease with pulmonary vascular disease

Pulmonary embolism


Collagen vascular disease

Pulmonary vasculitis

Sickle hemoglobinopathies

Portal hypertension

Left ventricular failure

Mitral valve disease

Cor triatriatum

Obstruction of major pulmonary veins

Congenital pulmonary vein stenosis

• Left atrial myxoma


Important Points:

  1. Pulmonary wedge pressure is not a feature of Precapillary Pulmonary hypertension.
  2. In precapillary pulmonary hypertension the abnormality that leads to elevated pulmonary pressure is located in the pulmonary artery or arterioles.
  3. The Left atrial pressure or Pulmonary capillary wedge pressure is essentially normal. 

Clinical Features

  1. Fatigue is the most common symptom
  2. Dyspnea
  3. Syncope and angina, particularly with exertion, are late manifestations of the disease, suggesting the presence of severe pulmonary hypertension causing reduced cardiac output.
  4. P2 is loud
  5. Narrow splitting of S2
  6. Systolic ejection click, the intensity of this click increases on expiration 



FVC is normal, FEV1 is normal & FEV1/FVC is normal.

  1. Pulmonary function studies to evaluate for the presence of other causes contributing to the development of pulmonary hypertension.
    1. In patients without underlying parenchymal lung disease who have PPH, there have mild restrictive changes but there is no evidence of obstruction.
    2. Hypoxemia is a feature and the diffusing capacity for carbon monoxide (DLCO) is reduced.
  2. The ECG may indicate right ventricular enlargement or show right ventricular strain.
  3. CXR may show enlargement of the pulmonary arteries.
  4. An echocardiogram can estimate pulmonary artery pressures, show evidence of tricuspid regurgitation.  

Important Points:


Features of Primary Pulmonary Hypertension / Idiopathic Pulmonary Arterial Hypertension
  1. Most common in Young women who are 20-40 years of Age (Ref. Robbin's 7th ed., Page - 745) (strong female predominance)
  2. Most common symptom is exertional dyspnea (predominant symptom is dyspnea)
  3. Pulmonary Function tests
    1. Are usually normal with the exception of DLCO which is characteristically reduced.
    2. Non obstructive PFT (FEV1/FVC>0.7 or 70%)
    3. Non restrictive PFT (FVC > 80%)
    4. DLCO 2 is reduced
      (Note: Mild restrictive effects can be seen in upto 20% of patients with advanced IPAH)   
  4. Exercise tolerance
    Exercise tolerance is markedly reduced
    (The exercise capacity of these patients appears to be limited by a low cardiac output because of a decrease in the functional pulmonary vascular bed)


  1. Calcium channel blockers
  2. Endothelin Receptor Antagonists: The endothelin receptor antagonists bosentan and ambrisentan are approved treatments of PAH. (Ref. Hari. 18th ed., Pg- 2079)
  3. Phosphodiesterase-5 Inhibitors – Sildenafil
  4. Prostacyclins analogue – Iloprost, Epoprostenol, Treprostinil
  5. Lung transplantation

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