1. How does blood circulate in the human body?
The heart is like a “pump” that drives the circulatory system to function properly. The blood circulation can be divided into two circuits: the systemic circulation, which delivers oxygen to various organs, and the pulmonary circulation, which supplies oxygen to the hypoxic blood. The heart drives these two processes with each beat.
Look at the body circulation first. The heart has four chambers. When it contracts, the left atrium and left ventricle in turn pump blood with high oxygen content (arterial blood) into the arteries and transport it to various tissues and organs. After the capillaries “unload” oxygen, the amount of oxygen in the blood drops, which is then recycled through the veins (venous blood), into the right atrium.
To increase the oxygen content in the venous blood, the body performs the pulmonary circulation along with the systemic circulation. The hypoxic blood in the right atrium is pumped into the right ventricle, the pulmonary artery in turn, and then reaches the capillaries of the lungs, where gas exchange takes place. Venous blood with low oxygen content is “oxygenated” into arterial blood, and then flows back to the left atrium through the pulmonary veins. This completes a pulmonary circulation, and then enters the next round of systemic circulation along the direction of the left atrium and left ventricle.
Image source: Zhanku Hailuo
Second, what is pulmonary hypertension?
The distance from the heart to the lungs is very short, and under normal conditions, the right heart does not need any special effort to pump blood into the pulmonary artery and to the lungs. However, if the pressure in the pulmonary artery is too high for various reasons, it is difficult for blood to be pumped into the pulmonary artery and pool in the right heart.
At this point, the heart needs to work harder. It’s like trying desperately to blow up a balloon, but the mouth of the balloon is pinched, and the person blowing up the balloon will become flushed and thick-necked. The same goes for the efforts made by the right heart. The long-term burden will increase, the heart will be strained and enlarged, the myocardium will be weakened, and right heart failure will occur. At the same time, the left heart cannot pump enough blood for the body because it does not get enough oxygen-rich blood, resulting in decreased cardiac output and tissue hypoxia.
What are the types of pulmonary hypertension?
According to the different causes of pulmonary arterial hypertension, it is generally divided into the following seven categories [1], and the treatment plans and recovery conditions of different types are also different.
Idiopathic pulmonary hypertension. The etiology is not completely clear, gene mutation is one of the possible causes, but unlike hereditary pulmonary arterial hypertension, there are many unclear etiologies and mechanisms in addition to genes.
Acute pulmonary vasodilation test positive pulmonary hypertension. The cause of this category is mainly pulmonary artery spasm. There is a special class of drugs, calcium channel blockers, which are very effective for this type. The severity of the disease and life expectancy are also better than other types.
Hereditary pulmonary hypertension. The onset is closely related to heredity and is related to certain gene mutations.
Pulmonary hypertension due to related diseases. By connective tissue diseases (such as systemic sclerosis, systemic lupus erythematosus, Sjögren’s syndrome), human immunodeficiency virus (HIV, also known as HIV) infection, portal hypertension, congenital heart disease, schistosomiasis, etc. Caused by a variety of reasons, for example, schistosome eggs can irritate the pulmonary blood vessels, resulting in structural abnormalities, connective tissue disease and inflammatory reactions caused by HIV infection can narrow the pulmonary arteries. In addition to the need for treatment of pulmonary hypertension, these patients should also be treated for the primary disease.
Pulmonary hypertension due to related drug toxicants. Exposure to certain drugs or poisons may also cause pulmonary hypertension, for example, the weight-loss drug fenfluramine, amirelex, dexfenfluramine, the hypoglycemic drug phenylfluramine, the tumor treatment drug dasatinib, the drug A Amylamphetamine, improperly processed poisonous rapeseed oil, etc.
Image source: Zhanku Hailuo
pulmonary veno-occlusive disease/pulmonary capillary hemangioma. Extremely rare, associated with a specific genetic mutation, and patients often die within 1 year of diagnosis.
Neonatal persistent pulmonary hypertension. It occurs mainly in neonates within a few hours of birth and has special diagnostic criteria.
Image source: Zhanku Hailuo
References
[1] Pulmonary Vascular Disease Group of Cardiovascular Branch of Chinese Medical Association, Editorial Board of Chinese Journal of Cardiovascular Diseases. Chinese Guidelines for the Diagnosis and Treatment of Pulmonary Hypertension 2018. Chinese Journal of Cardiovascular Diseases , 2018, 46(12): 933-964.
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