Pediatric myocarditis The heart is mainly composed of the myocardial part, except for the inner endocardium and the outer pericardium. The contraction of the heart is actually the contraction of the myocardium, and cardiac insufficiency or heart failure occurs as a result of varying degrees of reduction in myocardial contractility. The causes of myocarditis are multiple, the most common cause is infection, the most common is viral infection, there are about dozens of viruses that can cause myocarditis, other pathogens are bacteria, rickettsia, spirochetes, protozoa, etc. A variety of acute pediatric infectious diseases can complicate myocarditis. In addition, chemicals, disorders of electrolytes (potassium, sodium, chloride, calcium, etc.) in the blood can also cause myocardial changes. Severe anemia, connective tissue disease, and tumors can also involve the myocardium. Myocarditis is part of a systemic disease and can be classified as limited or diffuse depending on the extent of the lesion, and as acute or chronic depending on how quickly the disease develops. In children, acute myocarditis is the most common. Infectious myocarditis can occur in the acute phase of infectious disease or in the recovery phase. In the acute phase, it is most often caused by the direct action of viruses or bacteria and their toxins, while in the recovery phase, it may be caused by an immune response. Myocarditis may occur alone or in conjunction with endocarditis or pericarditis, with myocarditis and pericarditis being particularly common. Pediatric acute pericarditis The pericardium is located on the exterior of the heart and resembles the outer coat of the heart. The inner layer is also called the dirty layer, and the outer layer is also called the wall layer. Between the two layers of the pericardium is the pericardial cavity, which contains a small amount of fluid (about 10-15 ml) to prevent damage when the two layers rub together. The pericardium has a protective role for the heart. When the pericardium becomes inflamed, it is called pericarditis. Pericarditis can be caused by a variety of factors, the most common being infection-induced pericarditis. The most common pathogens are viruses and bacteria, including coxsackievirus, influenza virus, echovirus, adenovirus, hepatitis B virus, and infectious mononucleosis virus. Among the bacteria are staphylococci, pneumococci, streptococci, and Escherichia coli, which cause septic pericarditis. Tuberculous pericarditis caused by Mycobacterium tuberculosis is also common. In addition, connective tissue disease, leukemia, malignancy, uremia, etc. can also occur pericarditis. Pericarditis is mostly a local manifestation of systemic diseases and develops from sepsis and viremia in cases of infectious diseases. Constrictive pericarditis Constrictive pericarditis mostly develops from acute pericarditis. Constrictive pericarditis is a condition in which the two layers of the pericardium are adhered together and no pericardial cavity exists. Due to the adhesion of the pericardium, it is as if the heart is tightly wrapped by the pericardium, affecting the diastole and contraction of the heart. The compression of the heart is more pronounced than in the case of pericardial tamponade. The thickening and narrowing of the pericardium is more pronounced at the entrance to the superior and inferior vena cava, limiting the amount of venous blood returning to the heart. At the same time, the stroke volume of the left heart is restricted and reduced. Prolonged myocardial compression and ischemia, followed by myocardial fibrosis and impaired cardiac function, further reduce the heart’s stroke volume. The most common cases are tuberculous pericarditis and septic pericarditis. In these two types of pericardial cavity exudate contains a large amount of fibrin, fibrin, etc., which makes it easy for the pericardium to become adherent. Rheumatic heart disease Rheumatic fever is active rheumatic disease, which is a connective tissue disease, related to streptococcal infection, which develops 1 to 3 weeks after streptococcal infection, and is an infection that causes a metamorphic reaction in the body, and through the immune system, autoimmunity occurs and the disease develops, which is mostly seen in older children, and few people get the disease before the age of 4. Pediatric hypertension The severity of hypertensive symptoms is not only related to the height, but also to the speed of the rise in blood pressure. If the blood pressure rises slowly, even if it reaches a high level, the child’s performance is mild. Sometimes hypertension is detected only when the blood pressure is measured during a physical examination, and the symptoms of primary hypertension and secondary hypertension are more pronounced in the latter than in the former, even if the heights are the same. When blood pressure increases significantly, there can be dizziness, headache, nausea, vomiting and other manifestations, and in severe cases, hypertensive encephalopathy, confusion, visual impairment, convulsions, aphasia, hemiplegia, etc. Hypertension can cause heart disease, and those caused by primary hypertension appear after a longer period of time. Secondary hypertension can cause heart failure due to the presence of other factors, such as acute nephritis, of which hypertension is only one of the causes. Secondary hypertension still has other manifestations of the primary disease, such as swelling in kidney disease, heart panic, shortness of breath and heart murmur in heart disease, abnormal body shape and abnormal urination in endocrine disease.