OVERVIEW
• Pulmonary hypertension refers to elevated pressure in the blood vessels of the lung, which transport blood from the right ventricle to the lungs. It is a rare condition
• Pulmonary hypertension can be broadly divided into pulmonary arterial hypertension (PAH) that occurs due to disorders of the lung or arterial vasculature and pulmonary venous hypertension that occurs due to disorders of the pulmonary venous drainage or of the left heart

This topic will deal with pulmonary arterial hypertension

TYPES OF PULMONARY ARTERIAL HYPERTENSION (PH)
The clinical classification of is useful in understanding the aetiology and to plan treatment
• Group 1 Pulmonary arterial hypertension (PAH)
o idiopathic or primary PAH
o Can be associated with connective tissue disease such as scleroderma, certain drugs and toxins, HIV infection, chronic liver disease
• Group 2 Left heart disease
o Usually seen with left heart dysfunction either systolic, diastolic and valve disease
• Group 3 Lung disease
o Occurs in patients with COPD or interstitial lung disease, sleep apnea, exposure to high altitudes
• Group 4 Chronic thromboembolic pulmonary hypertension
• Group 5 Unclear and multifactorial mechanisms
o Rare diseases

RISK FACTORS OF PAH
• Young adult – Idiopathic pulmonary arterial hypertension
• Family history
• Raised BMI (increased incidence of sleep apnea)
• Taking illegal drugs, such as cocaine, appetite suppressants
• You take certain appetite-suppressant medications
• Living at high altitudes

PATHOLOGY OF PAH
PAH occurs when the pulmonary arteries and capillaries that transport blood from the right ventricle to lungs become narrowed or destroyed. This is thought to be triggered by a variety of factors (see above), but the exact cause why PAH occurs remains unknown. In some cases, PAH can be familial and is inherited

SYMPTOMS OF PAH
• Most common symptom is breathless on exertion that progressively worsens and then occurs even at rest
• Tiredness and fatigue
• Fainting episodes (syncope)
• Fast heart beat or palpitations
• Chest heaviness or pain
• Bluish tinge of lips and skin (cyanosis)
• Swelling (edema) in feet, legs and abdomen (ascites)

COMPLICATIONS OF PAH
• Right ventricular enlargement and failure
• Arrhythmias
• Bleeding into lung and potentially fatal hemoptysis

DIAGNOSIS OF PAH
There are many causes of PH and treatment depends on the etiology. If a diagnosis of PAH is suspected clinically, several tests will be performed to assess the severity and possible cause. These include

• Blood tests – to rule out or identify illnesses that can cause PH
• Echocardiogram – This is basically ultrasound of the heart to check the heart for size, blood flow, ability to function, and any abnormalities in the chambers or valves.
• Ventilation-perfusion scan – A dye is injected through an IV (intravenous line) to determine how well air and blood pass through lungs and presence of blood clots in the lungs.
• Pulmonary function test – measures amount of air and how fast the patient can expire into a machine. The test helps to diagnose lung diseases such as asthma or emphysema.
• CT scan – Specialized imaging test to look for changes or abnormalities in the lung tissue
• Heart catheterization – Minimally invasive procedure to measure the blood pressure in the heart and arteries. A thin, flexible tube is introduced into an arm, leg, or neck vein, and then guided slowly into the heart and lung artery. In pulmonary arterial hypertension mean pulmonary artery pressure >=25 mmHg at rest, measured at right heart catheterisation
• A dye may be injected into the heart arteries to look for blockages. This test can detect presence and severity of PAH and possible etiology in some cases
• Sleep study – Measures oxygen levels in the blood while sleeping. The test identifies occurrence of sleep apnea which can cause PAH
• Open-lung biopsy – Rarely, an open-lung biopsy may be performed to obtain a sample of lung tissue and to check histologically to determine the cause of secondary hypertension

STAGES OF PAH
The WHO has divided PAH into 4 stages to determine severity of disease. These are
• Class I – Pulmonary hypertension, with no symptoms while doing normal activity.
• Class II – Asymptomatic at rest, but symptoms such as shortness of breath, tiredness or chest pain are present while performing normal physical activity
• Class III – comfortable at rest, but have symptoms with minor physical exertion
• Class IV – Occurrence of symptoms at rest

TREATMENT OF PAH
There is no cure for PAH but the condition can be successfully controlled. Treatment may help improve symptoms and slow the progress of the disease

MEDICAL TREATMENT
Bosentan (Tracleer) – A tablet taken twice a day to reduce pressure in your lungs, improve exercise tolerance and slow down the disease.
Epoprostenol (Flolan)– This is administered continuously via an IV line. A permanent IV catheter is inserted into a vein along with a portable pump. This is reserved for patients with more serious illness. It decreases symptoms, and can prolong life.
Treprostinil (Tyvaso, Remodulin, Orenitram), another form of the Epoprostenol, is given four times a day as inhaler, oral medication or by injection.
Calcium channel blockers can be given to dilate narrowed blood vessels in the lungs but works only in some patients.
Soluble guanylate cyclase (SGC) stimulator – interact with nitric oxide to dilate narrowed pulmonary arteries and reduce pulmonary hypertension

SUPPORTIVE TREATMENTS
Diuretics and Digoxin are given to treat fluid build-up and heart failure
Anticoagulants such as warfarin are given to prevent clot formation
Oxygen therapy to improve oxygen levels in blood

SURGERY
Atrial septostomy – An opening is created between the upper left and right chambers of the heart (atria) to reduce the pressure in the right heart
Transplant – When patient is unresponsive to medications, a lung transplant or a heart-and-lung transplant may be considered particularly in younger patients with idiopathic PH

PROGNOSIS
Treatment options have improved for PAH although it cannot be cured. Early diagnosis and treatment is key to reduce risk of complications, and prolong survival in PAH. The 5 year survival following transplant is about 50-60%

RAPID REVIEW
Pulmonary arterial hypertension is elevated pressure in the pulmonary arteries and capillaries
In pulmonary arterial hypertension mean pulmonary artery pressure >=25 mmHg at rest, measured at right heart catheterisation
Idiopathic or primary PH is more common in younger patients
There is no cure for PAH but symptoms can be controlled and progression of disease can be slowed down with early diagnosis
In patients not responding to medical treatment, heart-lung transplant can help