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What causes pulmonary hypertension?

The small arteries of the lung narrow throughout the lungs. Pulmonary hypertension is the result of greater resistance to blood flow. As a result of the increased workload caused by this resistance, the right side of the heart becomes enlarged. Eventually, progressive heart failure may develop. Pulmonary hypertension may develop after pregnancy, hypothyroidism,

pulmonary embolism, autoimmune disorders, or human immunodeficiency virus (HIV) infection or result from the use of drugs such as appetite suppressants, oral contraceptives, and cocaine.

Primary pulmonary hypertension likely begins with spasm (contraction) of the muscle layer in the pulmonary arteries. Women are affected by primary pulmonary hypertension twice as often as men, and half of the people are 35 or older at the time of diagnosis. Normal pulmonary artery systolic pressure at rest is 18 to 25 mm Hg, with a mean pulmonary pressure ranging from 12 to 16 mm Hg. This low pressure is due to the large cross-sectional area of the pulmonary circulation, which results in low resistance. An increase in pulmonary vascular resistance or pulmonary blood flow results in pulmonary hypertension. In primary pulmonary hypertension, the pulmonary vasculature is the exclusive target of disease, although the pathogenesis remains speculative. The most widely accepted theory suggests that certain persons may be predisposed to primary pulmonary hypertension. In these persons, various stimuli may initiate the development of pulmonary arteriopathy. Vascular-wall remodeling, vasoconstriction and thrombosis in situ all play a role. Diet suppressants, cocaine, and pregnancy are some of the factors that are thought to trigger constriction or narrowing of the pulmonary artery. In about 6–10% of cases, primary pulmonary hypertension is inherited.

Secondary pulmonary hypertension can be associated with breathing disorders such as emphysema and bronchitis, or diseases such as scleroderma, systemic lupus erythematosus (SLE) or congenital heart disease involving heart valves, and pulmonary thromboembolism. Secondary pulmonary hypertension can be caused by any disease that impedes the flow of blood through the lungs or that causes sustained periods of low oxygen in the blood. One of the most common causes is chronic obstructive pulmonary disease. When the lungs are impaired by disease, it takes more effort to pump blood through them. Over time, chronic obstructive pulmonary disease destroys the small air sacs (alveoli) together with their small vessels (capillaries) in the lungs. The single most important cause of pulmonary hypertension in chronic obstructive pulmonary disease is the narrowing of the pulmonary artery that occurs as a result of low blood oxygen levels.

Pulmonary hypertension can be related to excessive pulmonary blood flow, such as occurs in congenital cardiac anomalies involving left to right shunts. Increased pulmonary pressure is also a potential consequence of any condition that impedes pulmonary venous drainage. Pulmonary hypertension frequently occurs in response to alveolar hypoxia. A reduction in oxygen tension causes pulmonary vasoconstriction by a variety of actions on endothelium and smooth muscle. Pulmonary hypertension may occur when blood flow through large pulmonary arteries is hindered. The classic cause is pulmonary embolism.

More information on pulmonary hypertension

What is pulmonary hypertension? - Pulmonary hypertension (PH) is a rare lung disorder in which the blood pressure in the pulmonary artery rises far above normal levels.
What is primary pulmonary hypertension? - Primary pulmonary hypertension is a rare, progressive disorder characterized by high blood pressure of the main artery of the lungs.
What is secondary pulmonary hypertension? - Secondary pulmonary hypertension is a disorder of the blood vessels in the lungs. It is the result of other lung diseases.
What causes pulmonary hypertension? - Pulmonary hypertension is the result of greater resistance to blood flow. Secondary pulmonary hypertension can be associated with breathing disorders.
What're the symptoms of pulmonary hypertension? - Symptoms of primary pulmonary hypertension include shortness of breath especially during exercise, chest pain, and fainting episodes.
How is pulmonary hypertension diagnosed? - Diagnostic tests for pulmonary hypertension involve blood tests, electrocardiography, arterial blood gas measurements, X-rays.
What's the treatment for pulmonary hypertension? - Treatment of pulmonary hypertension involves treating the underlying causes, using supplemental oxygen to increase blood oxygen levels, diuretics.
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