Idiopathic pulmonary hypertension is also known as primary pulmonary hypertension. The term “idiopathic” means that the cause is not very clear. The term “primary” means that it is not secondary to other diseases. Therefore, it is a spontaneous pulmonary hypertension of unknown origin. So, what is pulmonary hypertension? Pulmonary hypertension is hypertension of the pulmonary circulation. The human body has two sets of circulation: one is called the body circulation, which is pumped by the left ventricle and flows in the blood vessels of the whole body; the other is called the pulmonary circulation, which is pumped by the right ventricle and flows in the pulmonary vessels. High pressure in the body circulation is what we usually call hypertension, while high pressure in the pulmonary circulation is pulmonary hypertension. Why is the pulmonary artery pressure high? If we compare the pulmonary artery to a river, the main stem of this large river emanates from the right ventricle and then divides into two large tributaries that enter the left and right lungs, each of which continues to divide into many smaller tributaries until it becomes a myriad of small rivers and streams. These small rivers and streams are the small pulmonary arteries, which are located throughout our lungs and through which the oxygen we breathe is carried into our bloodstream. Although the small pulmonary arteries are small (they can only be seen under a microscope), the total number is very large and therefore determines the resistance of the entire pulmonary circulation. Once these small arteries become constricted or blocked, the resistance of the pulmonary circulation becomes very high, and the blood is “trapped” in the large pulmonary arteries, resulting in increased pressure and thus pulmonary hypertension. This is like a small river or stream that is blocked, and the water level of the larger river upstream will rise or even break its banks. What are the consequences of pulmonary hypertension? We know that blood flow in the body depends on the heart “pump”, this “pump” is divided into the left ventricle and the right ventricle, and the “pump” assigned to the pulmonary circulation is the right ventricle. Under normal circumstances, the resistance of the pulmonary circulation is very small, and the workload of driving the pulmonary circulation is not large, so the innate structure of the right ventricle is relatively unable to “suffer and work hard”. Once the resistance of the pulmonary circulation becomes greater and the pulmonary artery pressure becomes higher, the right ventricle, which is connected to the pulmonary artery, will have to exert more effort and do more work each time it contracts. At first, the right ventricle will be more enlarged and thickened “fatigue work” to compensate, but as the disease worsens the right ventricle will be more and more “force is not enough”, and eventually develop into right heart failure. It is clear that the root of pulmonary hypertension is in the lungs, but it is the heart that suffers the most, which is why the disease is seen in both respiratory and cardiology departments. There are two major causes of pulmonary hypertension: one is secondary to other diseases such as congenital heart disease, connective tissue disease, pulmonary embolism, etc.; the other is spontaneous, which is idiopathic pulmonary hypertension. Although the exact cause of idiopathic pulmonary hypertension is unknown, studies have shown that the disease is likely due to certain genetic mutations, triggered by certain environmental factors, which produce extensive constriction, thinning, and blockage lesions in the small pulmonary arteries. The most common and usually earliest symptoms of idiopathic pulmonary hypertension are decreased activity, feeling weak after activity, chest tightness, panic attacks, and other symptoms such as chest pain, syncope, hemoptysis, bruised lips, swelling, abdominal pain, and dry cough. Most of these symptoms are related to right heart failure. It is also right heart failure that usually leads to the deterioration of the patient’s condition or even death. The diagnosis of idiopathic pulmonary hypertension is an exclusionary diagnosis, which means that there is no one definitive test, and the diagnosis can only be made by a series of tests to exclude other possible diseases. Therefore, patients with idiopathic pulmonary hypertension routinely undergo a number of tests during their initial diagnosis. The purpose of these tests is not only to clarify the diagnosis, but also to determine the severity of the disease and to guide treatment. Two of the most important tests are echocardiography and cardiac catheterization. Echocardiography is a non-invasive test that can estimate pulmonary artery pressure, determine right heart function, and also rule out congenital heart disease and cardiomyopathy. Cardiac catheterization is an invasive test that can accurately measure pulmonary artery pressure, detect some cardiac abnormalities that may be missed by ultrasound, rule out pulmonary embolism, and guide the use of medication for treatment. During the treatment of idiopathic pulmonary hypertension, periodic review of echocardiography, blood BNP, and 6-minute walk test are also needed to evaluate the effect of treatment. The current main treatment for idiopathic pulmonary hypertension is long-term drug therapy. We know that the root cause of this disease is in the pulmonary vasculature, but the symptoms and life-threatening effects are mainly due to the involvement of the heart, so there are two main groups of drugs for treatment: those for the pulmonary vessels and those for the heart. The cardiac drugs are those that improve right heart function, including diuretics and cardiac stimulants, which can improve symptoms but have limited effect because they do not address the root of the problem. Drugs targeting the pulmonary vasculature include pulmonary vasodilators and anticoagulants. There are three main classes of drugs that are specifically designed to expand the pulmonary vasculature, also called “targeted drugs”, which have been developed in the last decade or so, namely endothelin receptor antagonists (bosentan, anlisentan), prostacyclin and analogues (iloprost, travoprost, beprost), phosphodiesterase 5 inhibitors (sildenafil, tadalafil ). These drugs are taken orally, as well as by inhalation and injection. Before the emergence of targeted drugs, the treatment of idiopathic pulmonary hypertension could only apply some drugs to improve cardiac function. The emergence of targeted drugs has greatly improved the exercise tolerance, quality of life and survival time of patients with idiopathic pulmonary hypertension, and has become the main method of treatment for this disease. However, the current price of targeted drugs is generally high, which increases the financial burden of patients to a certain extent. For a portion of patients with positive pulmonary vascular response on cardiac catheterization, they can be treated with inexpensive calcium channel blockers instead of targeted drugs, but the efficacy and side effects need to be closely observed during the treatment. In addition, oxygen can also dilate the pulmonary vasculature to some extent and improve bruising, and it is inexpensive and can be used as an adjunctive treatment. In addition to pulmonary vasodilators, anticoagulants are usually used in the treatment of idiopathic pulmonary hypertension to prevent small blood clots in the pulmonary vessels from blocking the vessels and aggravating the disease. Patients with idiopathic pulmonary hypertension may experience a sudden increase in pulmonary artery pressure and aggravation of the disease under special circumstances, such as strenuous exercise, exertion, or respiratory tract infection. Therefore, along with drug treatment, attention should also be paid to avoid strenuous exercise and overexertion, prevent respiratory infections, avoid pregnancy, avoid going to high altitude and low oxygen areas, and avoid high temperature bathing. Surgery is not currently the main treatment for idiopathic pulmonary hypertension. For some patients with very severe right heart failure, atrial septostomy and pulmonary body bypass surgery can be done to relieve the symptoms, but it is not a radical cure. Lung transplantation is theoretically a radical treatment, but currently it is not yet commonly performed due to few donors, high cost, high risk, and unsatisfactory long-term survival, and is only used for some patients with advanced and severe disease that is difficult to control with drugs. For a long time, idiopathic pulmonary hypertension has been regarded as a disease with poor prognosis and no cure, but the continuous progress of modern medical tools, especially the emergence of targeted drugs, is providing better and better prospects for improving the prognosis of this disease. Therefore, patients and their families should have strong confidence and actively cooperate with doctors in the examination and treatment. In addition, idiopathic pulmonary hypertension has a certain degree of heredity, and several genetic mutations related to the disease have been identified. Therefore, patients and relatives diagnosed with idiopathic pulmonary hypertension should undergo relevant genetic tests to avoid having another child with the disease in the future.