Pulmonary hypertension

• Pulmonary hypertension (PH) is a pathophysiological disorder occurring when mean pulmonary artery pressure is >25mmHg at rest when assessed with right heart catheterisation
• Pulmonary hypertension is an umbrella term for many different diseases which lead to increased pressure in the pulmonary arteries
• Pulmonary arterial hypertension (PAH) is a subtype of PH, characterised by pre-capillary pulmonary hypertension in the absence of other causes (e.g. lung disease or other systemic diseases)
• In general, pulmonary hypertension occurs when the pulmonary arteries become narrowed (due to hypoxic pulmonary vasoconstriction or thrombosis), thickened or damaged causing increased pressure in the vessels
• Left heart disease can reduce flow from the right side of the heart, and in turn increase the pulmonary artery pressure
• Subtypes:

  • Pulmonary arterial hypertension - can be idiopathic, inherited or associated with other systemic diseases e.g. connective tissue disorders
  • Pulmonary hypertension due to left heart disease
  • Pulmonary hypertension due to lung disease e.g. COPD, OSA
  • Chronic thromboembolic pulmonary hypertension (CTEPH) and other pulmonary artery obstructions - chronic pulmonary embolism or intravascular tumours
  • Pulmonary hypertension with unclear/multifactorial mechanisms e.g. sarcoidosis
• Risk factors are related to the subtype:

  • PAH - family history and female gender
  • Pre-existing diseases: lung disease, left heart disease, congenital heart disease and connective tissue disorders
  • Obesity and sleep apnoea
  • Prolonged exposure to high altitude
• Symptoms:

  • Related to gradually worsening right ventricular function
  • SOB
  • Weakness and fatigue
  • Chest pain
  • Syncope
  • Haemoptysis (uncommon but may be present in chronic thromboembolic disease)
• SSRIs and weight loss medication are linked to pulmonary hypertension
• Exam findings:

  • Loud pulmonary component of S2
  • Third heart sound
  • Pansystolic murmur - tricuspid regurgitation
  • Diastolic murmur - pulmonary regurgitation
  • Later stages - oedema, parasternal heave, elevated JVP and hepatomegaly
• The most useful initial investigation in suspected cases of pulmonary hypertension is an echocardiogram to estimate pulmonary pressure. In cases of suspected pulmonary arterial hypertension, right heart catheterisation is usually performed. 
• ECG: to look for evidence of right ventricular strain including right ventricular hypertrophy, right axis deviation, right bundle branch block, and arrhythmias (atrial flutter and fibrillation may be present in later stages). A normal ECG does not exclude PH.
• Lab investigations:

  • Liver function tests: to assess for liver disease
  • Serology: to look for HIV and hepatitis
  • Autoimmune screen: to look for evidence of connective tissue disease (e.g. anti-centromere antibodies and U3-RNP in scleroderma)
  • Arterial blood gas: to look for evidence of respiratory disease
• Imaging:

  • CXR - to assess for signs of underlying lung disease or left ventricular dysfunction. PAH may present with central pulmonary arterial dilation, pruning of peripheral vessels, right atrial and ventricular enlargement.
  • Echo - asses right ventricular function and estimate pulmonary arterial pressure
  • V/Q scan - look for chronic thromboembolic disease or other underlying lung disease
  • Cardiac MRI
• Other investigations:

  • Pulmonary function tests and overnight oximetry: to look for signs of underlying lung disease as an aetiology. PAH can lead to mild/moderate reduction in lung volumes.
  • Right heart catheterisation: used to diagnose PAH, assess severity and guide treatment.
  • Genetic testing: in specific patients with PAH.
• Management varies depending on the underlying cause of PH.

  It is important to treat the underlying cause and refer to specialist services for PAH or severe PH.
• All patients should be advised on the following conservative measures:1

  • Exercise (within symptom limits) and rehabilitation
  • Influenza and pneumococcal vaccination
  • Contraceptive advice (pregnancy is associated with 30-50% mortality in PAH patients)
  • Psychosocial support
• Medical management:

  • Diuretics: for symptomatic benefits in decompensated right heart failure.
  • Long term oxygen therapy including ambulatory oxygen.
  • Digoxin: improves cardiac output acutely but has unknown efficacy in the long term.
  • Oral anticoagulation: there is thought to be increased risk of thrombosis intrinsically as part of the disease process and through comorbid factors including immobility and heart failure.
  • Specific drug therapy: calcium channel blockers, endothelin receptor antagonists (i.e. bosentan), phosphodiesterase inhibitors (e.g. sildenafil)
• Cardiopulmonary transplant is used in selected cases. There is a good prognosis with long term immunosuppressive therapy
• Complications relate to worsening right heart failure and include:

  • Peripheral oedema
  • Severe exertional dyspnoea

  Pneumonia and sudden cardiac death (including during childbirth) can also occur.