Pulmonary Hypertension : Epidemiology, Pathology, Classical Features

Traditional definition

• If the mean pulmonary arterial pressure, in any child or adult is equal to or more than 25 mmHg at rest as measured by right heart catheterization, that is called as pulmonary hypertension. (5th WSPH, 2013; AAP, AHA). As per Nelson, If the mean pulmonary arterial pressure, in Any child or adult is equal to or more than 200 mmHg at rest as measured by right heart catheterization, that is called as pulmonary hypertension. (6th WSPH, 2018; AAP, AHA). This is the latest definition of Pulmonary hypertension.

Difference Between Pulmonary Hypertension And Pulmonary Arterial Hypertension

• It is important to understand that they are synonymously used but they are not same. There is a difference between these two terms.  Pulmonary arterial hypertension (PAH) is considered to be a subtype of pulmonary hypertension (PH). PAH is also called as pre capillary pulmonary hypertension.

Definition of Pulmonary Arterial Hypertension

• There should be normal pulmonary, along with capillary wedge pressure. So, the pulmonary capillary wedge pressure, which is labelled as pulmonary arterial wedge pressure, it should be equal to or less than 15mm Hg. Moreover, the pulmonary vascular resistance, must be greater than three wood units per square meter.

Epidemiology Of Pulmonary Hypertension

• Pulmonary hypertension can occur at any age. Idiopathic or familial cases which comprise about 10 to 15 percent. Females are more commonly affected than means by a ratio of 1.7 ratio 1 in the other forms.  The top causes of pulmonary hypertension are the following: Congenital heart disease, is the primary cause, and comprises 40 to 55 percent. Second most common cause is chronic respiratory disorders, which is 20 to 35 percent. Third most common cause is idiopathic or familial disease, which is responsible in 10 to 15 percent. There is a vascular Tropic virus called as Human herpes virus (HHV-8), which is a viral trigger for pulmonary hypertension to develop.

What Is BMPR 2?

• It stands for bone morphogenic protein receptor-2. This belongs to the family of tumour, necrosis Factor Alpha receptors, which are basically protein receptors.  Mutations in BMPR-2 gene are considered to be the most common inherited cause or most common genetic cause of pulmonary hypertension. It is present on chromosome 2q33.  Gene is implicated in 70% cases of familial pulmonary hypertension and 10-15% cases of idiopathic primary pulmonary hypertension. 

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Pathological Features In Pulmonary Hypertension

• There are five pathological features of Pulmonary hypertension.

Consequences of Pulmonary Hypertension

• It will result in increase in the back pressure changes.  That is, it will increase the afterload to the right ventricle due to this. 

The right ventricle will now add have to generate more pressure to send blood into the loo into the pulmonary system and this will lead to concentric type of right ventricular hypertrophy. This remodelling will make the RV prone to failure. There will be decreased cardiac output once failure and shoes, so decreased cardiac output will be present. In the right ventricle which will ultimately result in the involvement of the left ventricle as well. In addition, due to increased back pressure, you will find that many of these patients will develop features of pulmonary regurgitation.

Classical Features Of Pulmonary Hypertension

• The first and the most common symptom that we find is exercise intolerance, also known as dyspnea, along with easy fatigability. Syncope occurring in 30% of paediatric patients. Patients may also be seen with precordial chest pain, dizziness and headache, and peripheral cyanosis. In the later stages, cold and greyish extremities can be noticed. Signs of right-sided heart failure can be seen. Raised JVP with prominent A waves. Hepatomegaly and pedal edema. Cardiomegaly and right ventricular heave. In heart sounds, the S1 shall be followed with an ejection click. S2 will be loud and narrowly split. Gallop Rhythm may be present. Decrescendo which means it is maximally loud at the beginning and then comes down, will be noticed. A holosystolic murmur due to TR.

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Investigations In Pulmonary Hypertension

• Findings seen in an X-ray are A prominent Central or mean pulmonary artery can be seen. A very prominent right-sided hilar region, which will be due to prominent right pulmonary artery and its branches. The peripheral pruning of the pulmonary artery can be noticed. The vascularity will dramatically decrease towards the peripheries.
• Findings that can be seen in an ECG- ECG will show the presence of right-sided heart enlargement, right-sided failure features. Right Axis deviation can be seen. Prominent P waves can be seen. The ratio between the R wave and the S wave, shall be greater than 1.
• Echo and Doppler studies are essential: They are useful to identify the coexisting CHD in the patients. They are also helpful in identifying the QP and QS ratios. 
• Cardiac Catheterization helps in distinguishing the type of pulmonary hypertension, and is thus known as a gold standard test. Risky in critically elevated PH. Helps to determine PAP, PAWP/PCWP, LVEDP and PVR. Also useful for measuring the individual chamber pressures for underlying congenital heart disease.

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Determination Of Risk Factors Of Pulmonary Hypertension

Treatment Of Pulmonary Hypertension

• It has been found that most of the types of pulmonary hypertension are progressive in nature, with no definite cure.  When it comes to non-conventional treatment modalities, there are three treatment options- Oxygen will be administered only in those patients who are having hypoxemia and severe RVF. Diuretics can be given to patients to improve the symptoms.  Anticoagulants is often a part of the treatment plan. Patients undergo acute vasoreactivity testing during cardiac catheterization.  Those showing positive test benefit from CCBs (example: Amlodipine, Nifedipine, verapamil).
• Treatment modalities, especially for children are: PDE-5 inhibitors: Sildenafil, Tadalafil . ERA: Endothelin Receptor Antagonists (Bosentan which is a non-specific ERA, Ambrisentan which is a specific ERA) . Prostacyclin (example, Epoprostenol) and PGI2 analogous (example, lloprost, Teeprostin which has availability issue in India)
• The definitive treatment modality for pulmonary hypertension is heart-lung transplant.

Management Flowchart For Pulmonary Hypertension

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Prognosis For Pulmonary Hypertension

• It is determined by the underlying Etiology and the right ventricular function. Overall survival is poor only two to three years are available. As seen from the time of diagnosis in patients who have genetic form or idiopathic form of pulmonary hypertension. Acquired prognosis have better outcome. Patients with PH diagnosed in infancy, especially those in premature infants with chronic disease, or with pulmonary vein stenosis often have rapid progression and high mortality.  In patients with severe PH and low CO, the terminal event is usually an arrhythmia.  The prognosis of pulmonary arterial hypertension is better. The prognosis for pulmonary hypertension diagnosed at infancy is poor.

Developmental Lung Diseases Associated With Pulmonary Hypertension

• Congenital diaphragmatic hernia, Bronchopulmonary dysplasia., Alveolar capillary dysplasia (ACD), ACD with misalignment of veins, Lung hypoplasia (“primary” or “secondary”). Surfactant protein abnormalities: SP-B deficiency SP-C deficiency, ATP-binding cassette A3 mutation, TTF1/Nkx2.1 homeobox mutation. Pulmonary interstitial glycogenosis, Pulmonary alveolar proteinosis., Pulmonary lymphangiectasia. 

PPHN One-liners Asked In Past Exams

• Also known as persistent foetal circulation. There is absolute/ relative failure of pulmonary pressures to fall postnatally. Seen in multiple conditions that act as risk factors, many of which: Idiopathic, CDH, Birth asphyxia, Meconium aspiration syndrome, Pleural effusions, RDS, Neonatal sepsis.
• Management: Inhaled NO (iNO). It has been shown to reduce the need for ECMO by 40%. The starting dose is 20 parts per million. Sildenafil is used as a substitute for iNO. In vast cases, we need to opt for ECMO and eventually lung transplant will be needed in these patients.

Hope you found this blog helpful for your NEET SS Pediatrics Cardiology preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.