PULMONARY HYPERTENSION

Pulmonary Hypertension (PH ) is a progressive condition in which there is an increase in pressure in the pulmonary arteries. This ultimately leads to increased pressure leading to right heart failure and death.

What is pulmonary circulation?

Our heart has 4 chambers i.e. left atrium, left ventricle, right atrium and right ventricle. The pulmonary artery carries the impure blood from the right ventricle to the lungs while the pulmonary vein carries pure blood from the lungs to the left atrium.

What Is Pulmonary Hypertension (PH)?

Increase in pressure in the pulmonary artery i.e. the blood vessel which carries blood from the right side of the heart to the lungs results in the development of pulmonary hypertension. There are multiple reasons which might lead to the increase in pulmonary arterial pressure. The normal mean pulmonary artery (PA) pressure (mPAP) at rest is 14 ± 3.3 mm Hg with the upper level of normal being 20.6 mm Hg. An increase in mPAP above 25 mm Hg as assessed by right heart catheterization is defined as Pulmonary Hypertension.

Classification of Pulmonary Hypertension

Pulmonary hypertension is classified into 5 groups as follows:

Group 1

This group consists of pulmonary arterial hypertension (PAH). This includes Idiopathic PAH, Heritable PAH, drug and toxin induced and PAH associated with connective tissue disease, HIV infection, portal hypertension and congenital heart disease resistance, which ultimately leads to right heart failure and death.

Group 2 consists of Pulmonary Hypertension secondary to left heart disease.

Group 3 consists of Pulmonary Hypertension secondary to lung disease like COPD and interstitial

lung disease.

Group 4 consists of chronic thromboembolic Pulmonary Hypertension

Group 5 consists of Pulmonary Hypertension with unclear multifactorial mechanisms

Symptoms of Pulmonary Hypertension:

The following symptoms are seen in patients of pulmonary hypertension

• Shortness of breath. This is initially seen while exercising and eventually can also be seen at rest.
• Fatigue
• Swelling in the ankles and the legs (edema)
• Dizziness or fainting spells
• Cyanosis i.e. bluish color of the lips and the skin can also be seen

Risk Factors:

• Family History - Those people who have a family history of 2 or more members of the family having pulmonary arterial hypertension (PAH) are at a higher risk of developing PAH
• Obesity and Obstructive Sleep Apnea -  Obese people having a history of obstructive sleep apnea are more likely to develop PH
• Gender - Females are more susceptible to develop PAH
• High Altitude - Staying at a high altitude for years can make people predisposed to PH. Travelling to high altitude places may also aggravate PH symptoms.
• Other Conditions - Many people who are diagnosed with PH also have other concomitant medical conditions. Congenital heart disease, Chronic Obstructive Pulmonary Disease (COPPD), mixed-connective tissue disease, sleep apnea, liver disease and lupus

Diagnosis

For diagnosis of pulmonary hypertension, the pulmonologist will take your detailed history and do a physical examination. Following tests may also be carried

1. Echocardiography -  An echocardiography helps the physician understand how the heart and its valves are working. It also shows the size and thickness of the right ventricle and the pressure in the pulmonary arteries.

2. Right Heart Catheterization – In case the echocardiogram demonstrates increased pressure in the pulmonary artery, the physician will confirm it by doing a right heart catheterization. This procedure allows the physician to directly measure the pressure in the pulmonary artery and the right ventricle. During this procedure, the physician will insert a catheter in a vein, usually in the groin. The catheter is then gently guided into the right ventricle and the pulmonary artery .

3. Computerized Tomography (CT) Scan – Your physician might also request for a CT scan to understand if there are any underlying lung pathologies which might have resulted in the development of pulmonary hypertension.

4. Magnetic Resonance Imaging – Your physician might also order an MRI test to study the blood flow in the pulmonary arteries and understand the working of the right ventricle.

5. Lung Function Tests – Pulmonary hypertension is the common complication of Chronic Obstructive Lung Disease (COPD). Your physician might also order lung function tests to determine if you have an obstructive/restrictive lung pathology.

6. Ventilation/Perfusion (V/Q Scan)-  This is useful to determine if there is a blood clot in the lungs and if it is leading to pulmonary hypertension. In this test radioisotopes are injected in the vein. It measures the breathing (ventilation) and circulation (perfusion) in all areas of the lungs.

Treatment of Pulmonary Hypertension:

Currently there is no cure for pulmonary hypertension. Whenever there is an underlying cause for pulmonary hypertension, the treatment is directed towards fixing the underlying cause.

The following medications are used for treatment of pulmonary hypertension:

Endothelin receptor antagonists: Endothelin-1 is a potent vasoconstrictor which plays a role in the pathogenesis of pulmonary hypertension. Drugs which block the endothelin receptor are used in the treatment of pulmonary hypertension. Bosentan, ambrisentan and macitentan are the examples of the drugs which belong to this class.

Phosphodiesterase Inhibitors (PDE-5 inhibitors): These drugs inhibit the PDE-5 enzyme and promote relaxation of the pulmonary arteries. Sildenafil and tadalafil are the two drugs from this class which are approved for the treatment of pulmonary hypertension.

Soluble Guanylate Cyclase Activators: These drugs activate the enzyme soluble guanylate cyclase and promote the relaxation of the pulmonary vessels. It is used for the treatment of pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension

Prostanoids: These are another group of drugs which are used in the treatment of pulmonary hypertension. Epoprostenol, iloprost and treprostinil are the three drugs in this class which have been approved for the treatment of pulmonary hypertension.

Surgical Treatment:

In case medical treatment is unable to control the signs and symptoms of pulmonary hypertension, surgery may be performed.

Following surgical procedures are generally performed:

Pulmonary Endarterectomy -  In this procedure clots are removed from the pulmonary arteries in people with chronic thromboembolic pulmonary hypertension.

Balloon Pulmonary Angioplasty - In this procedure, a  balloon is guided into the pulmonary arteries and inflated for a few seconds to push the blockage aside and restore blood flow to the lung. This is generally carried out on patients in whom it is not possible to carry out a pulmonary endarterectomy.

Atrial Septostomy -  In this procedure, the surgeon creates an opening between the upper left and right chambers of the heart to relieve the pressure on the right side of the heart.

Lung or heart-lung transplant: This may be recommended, especially for younger people who have idiopathic pulmonary arterial hypertension.

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References:

• https://www.nhs.uk/conditions/pulmonary-hypertension/treatment/
• https://www.cdc.gov/heartdisease/pulmonary_hypertension.htm
• https://www.uclahealth.org/lungcancer/lung-ventilation
• https://phassociation.org/patients/aboutph/diseases-and-conditions-associated-with-ph/
• https://phassociation.org/patients/aboutph/risk-factors/
• Badesch DB, McLaughlin VV, Delcroix M, Vizza CD, Olschewski H, Sitbon O, Barst RJ. Prostanoid therapy for pulmonary arterial hypertension. J Am Coll Cardiol. 2004 Jun 16;43(12 Suppl S):56S-61S. doi: 10.1016/j.jacc.2004.02.036. PMID: 15194179.
• https://www.mayoclinic.org/diseases-conditions/pulmonary-hypertension/symptoms-causes/syc-20350697

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