The rare and life-threatening disease pulmonary hypertension (PH) is characterized by high blood pressure in the lungs and occurs when the pulmonary arteries become clogged and narrowed. The pulmonary arteries are the vessels responsible for the transport of blood from the heart to the lungs. Due to this condition, the heart, and particularly the right heart ventricle, becomes overworked in order to properly pump the blood, which can result in enlargement and weakening of the organ and ultimately,death.
Pathophysiology refers to a derangement or defect that occurs in the body and is characteristic of specific diseases. In the case of pulmonary hypertension, the pathophysiology of the disease is not always completely identified, but the two main mechanisms of pulmonary hypertension pathophysiology are increased pulmonary vascular resistance and increased pulmonary venous pressure.
Increased Pulmonary Vascular Resistance As Pulmonary Hypertension Pathophysiology
Increased pulmonary vascular resistance is the result of the obliteration of the pulmonary vascular walls, pathologic vasoconstriction or both. Vascular wall remodeling that is associated with pulmonary hypertension is caused by different factors, such as pathologic vasoconstriction endothelial and smooth muscle proliferation, hypertrophy, and chronic inflammation. Additionally, vasoconstriction is related to thromboxane and endothelin-1 enhanced activity.
The vascular obstruction is also responsible for an increase in pulmonary pressure and endothelium injuries that activate coagulation. Due to this capacity, pulmonary hypertension gets worse, which is exacerbated by a decrease in tissue plasminogen activator activity that occurs as consequence of platelet dysfunction, plasminogen activator inhibitor type 1 and fibrinopeptide A high activity and thrombotic coagulopathy. If platelets are stimulated they segregate substances able to enhance fibroblasts proliferation and soften the muscle cells.
Increased Pulmonary Venous Pressure As Pulmonary Hypertension Pathophysiology
The other mechanism of pulmonary hypertension pathophysiogy is increased pulmonary venous pressure, which is often a result of other medical conditions that harm the left side of the heart and increase pressure in the left heart ventricle. Due to the excessive stress, the pulmonary arteries also gain high pressure, which can result in acute injuries in the alveolar-capillary wall and subsequent edema. In the long-term, it can also cause irreversible thickening of the walls of the alveolar-capillary membrane, compromising lung function.
Pulmonary hypertension patients, particularly older women, may suffer pulmonary venous hypertension is in left heart failure with preserved ejection fraction (HF-PEF). It is even more dangerous for patients who also suffer from metabolic syndrome. Patients have little chance of survival if the mean pulmonary artery pressure to pulmonary artery occlusion pressure gradient or transpulmonary gradient is higher than 12 mm Hg or the pulmonary artery diastolic pressure to pulmonary artery occlusion pressure gradient is higher than 6 mm Hg.
Unknown Pulmonary Hypertension Pathophysiology
Idiopathic pulmonary hypertension is diagnosed when the cause for the disease is unknown. There is little understanding of the idiopathic pulmonary hypertension pathophysiology. It is however known that in some cases there is an endothelium defect, which results in the increase of the lung susceptibility to pulmonary vascular damages. Due to this risk, a series of problems can occur, including vascular scarring, endothelial dysfunction, and intimal or medial proliferation also known as smooth muscle.
In 15 to 20% of the cases, if there is a history of pulmonary hypertension in the family, which leads to believe that in can be related to a genetic defect. Researchers have focused on the BMPR-II gene to explain the heredity disease, but no conclusions were found yet. Five other mutations – ALK1, ENG, SMAD9, CAV1 and KCNK3 – may also be in the foundations of idiopathic pulmonary hypertension pathophysiology.
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