Pulmonary Arterial Hypertension
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Clinic
- PH or PHTN is a condition of increased blood pressure in the arteries of the lungs.
- It has two types
- Primary PH (resulting from a disease of the pulmonary arteries)
- Secondary PH (resulting secondary to other, non-vascular causes).
Signs / Symptoms
- Shortness of breath / Cyanosis
- Fatigue
- Chest pain
- Palpitations
- Right-sided abdominal pain
- Poor appetite
- Lightheadedness / Fainting
- Swelling (Legs/ Ankles)
Pathogenesis
- The pathogenesis of pulmonary arterial hypertension (WHO Group I) involves the narrowing of blood vessels connected to and within the lungs.
- This makes it harder for the heart to pump blood through the lungs, as it is much harder to make water flow through a narrow pipe as opposed to a wide one.
- Over time, the affected blood vessels become stiffer and thicker, in a process known as fibrosis
- The mechanisms involved in this narrowing process include vasoconstriction, thrombosis, and vascular remodeling (excessive cellular proliferation, fibrosis, and reduced apoptosis/programmed cell death in the vessel walls, caused by inflammation, disordered metabolism and dysregulation of certain growth factors).
- This further increases the blood pressure within the lungs and impairs their blood flow.
Molecular pathology
- The molecular mechanism is not known yet, but it is believed that the endothelial dysfunction results in a decrease in the synthesis of endothelium-derived vasodilators such as nitric oxide and prostacyclin.
- Moreover, there is a stimulation of the synthesis of vasoconstrictors such as thromboxane and vascular endothelial growth factor (VEGF).
- These result in a severe vasoconstriction and vascular smooth muscle and adventitial hypertrophy characteristic of patients with PAH.