Noncompaction of the ventricular myocardium is a rare congenital cardiac malformation due to failure of myocardial densification during embryogenesis, characterized anatomically by excessive protrusion of myocardial trabeculae in the ventricular wall and deep sunken fossa between the trabeculae. It is also known as 1eft ventricular noncompaction (LVNC) because it mainly involves the left ventricle. When present alone, it is called isolated myocardial densification insufficiency, with an annual incidence of 0.05% to 0.24%. The disease can also be combined with other congenital heart diseases, the most common being atrial septal defect, followed by coronary artery anomalies (left coronary artery originating from the pulmonary artery, coronary ventricular fistula), conical arterial trunk anomalies (aortic atresia, bilobed aortic valve, aortic constriction, pulmonary valve agenesis, pulmonary atresia, tricuspid atresia, transposition of the great arteries, permanent arterial trunk), ventricular septal defect, tricuspid valve subluxation malformation, pulmonary vein ectopic drainage and left heart dysplasia syndrome. The main clinical manifestations are heart failure, arrhythmias and endocardial thrombosis with embolism in the body circulation. There is no specific treatment available. The disease has a tendency to run in families, with 12% to 50% of patients having a family history. Most of the patients have autosomal dominant inheritance, but a few cases have X-chromosome chain recessive inheritance and mitochondrial inheritance. LVNC occurs mostly in the left ventricle, with a few cases involving the right ventricle and some cases involving both ventricles. The outer layer is the epicardial zone, which is composed of densified myocardium, and the inner layer is the endocardial zone, which is composed of non-densified myocardium, showing numerous myocardial trabeculae protruding into the ventricular cavity and deep trabecular fossae, which often reach the outer 1/3 of the ventricular wall and communicate with the ventricular cavity. Clinical manifestations The disease is more common in children, with the age of onset ranging from 1 day to 80 years after birth, and the average age of onset in children is 90 days to 3 or 9 years. There are more males than females. According to the aforementioned 60 cases reported in China, there were 39 males and 21 females, and the ratio of males to females was 1,6:1. The clinical manifestations were mild and severe. The clinical manifestations vary from asymptomatic in mild cases to progressive deterioration of cardiac function leading to congestive heart failure, ventricular arrhythmias, embolism, and even sudden death in severe cases. The time of appearance and severity of symptoms of heart failure are related to the extent of myocardial involvement. Most of the arrhythmias are fatal ventricular arrhythmias, such as ventricular tachycardia, some of which can be in the form of tip-twisting; they can also be atrial arrhythmias, such as atrial precontraction and atrial fibrillation, etc. A few patients can develop atrioventricular block, and complete atrioventricular block is mostly seen in children. Complete AV block is usually seen in children. In children, it is often combined with preexcitation syndrome and is usually a right-sided anterior septal collateral tract, which can be complicated by supraventricular tachycardia. Patients may show recurrent palpitations, even syncope and sudden death. 3, thrombosis cardiac thrombosis and body circulation thromboembolic events are due to atrial fibrillation and slow blood flow in the deep crypt leading to ventricular appendage thrombus formation, embolus dislodgement, causing body circulation embolism such as cerebral infarction. 4.Other Child patients may also have malformations other than the heart, such as developmental delay, facial abnormalities, cleft palate, cataract, scoliosis, small genitalia, etc., while developmental delay and facial abnormalities are more common. The special facial features mainly include prominent forehead, nystagmus, low ear position and high palatal arch. The majority of cases have electrocardiogram changes, and there are often multiple changes. The most common ones are: (1) T-wave inversion and ST-segment downshift; (2) conduction block, such as right bundle branch block (occasionally left bundle branch block) and atrioventricular block; (3) cardiac hypertrophy, such as left ventricular hypertrophy, left atrial hypertrophy, right atrial hypertrophy and biventricular hypertrophy; (4) rhythm disturbances, such as premature ventricular beats, persistent ventricular tachycardia, paroxysmal supraventricular tachycardia, atrial fibrillation, sinus bradycardia, etc. 2. Echocardiography Two-dimensional echocardiography is of decisive value for diagnosis. In order to show myocardial trabecular lesions, the exploration site should be chosen as parasternal, apical and subxiphoid. In most cases, the left heart chamber is enlarged, and in a few cases, the right or both chambers are enlarged, often in combination with atrioventricular valve insufficiency. In this disease, many protruding and enlarged myocardial trabeculae can be detected in the cardiac cavity, which are arranged in a honeycomb pattern, and the number of myocardial trabeculae increases gradually from the middle of the septum to the apical part of the heart, and deep sunken fossae of different sizes can be seen between the trabeculae. 3.CT and MRI examination CT showed the 2-layer structure of coarse myocardial trabeculae formation layer and dense layer of the left ventricular wall. 4.Cardiac catheterization and cardiovascular angiography Left ventricular angiography showed sponge-like changes in diastole and contrast retention between trabeculae in systole. In most cases, myocardial hypokinesis with incomplete densification is also seen. V. Diagnosis The age of onset and clinical manifestations of this disease are highly variable, and the symptoms and signs are non-specific, making it difficult to confirm the diagnosis by symptoms and signs alone. In 2001, Jenni et al. summarized the following echocardiographic diagnostic criteria: (1) multiple, coarse, bulging myocardial trabeculae and deep crypt-like structures in the ventricular cavity can be detected; (2) the ratio of thick, non-dense endocardial layer to thin, dense epicardial layer is greater than 1,4 in children and greater than 2 in adults; (3) color Doppler reveals small myocardial motion. (3) Color Doppler shows that there is low velocity blood flow between the trabeculae and the chambers of the heart; (4) The affected ventricular chambers are enlarged, the motion is reduced, and myocardial systolic and diastolic functions are reduced; (5) The presence of other congenital or acquired heart diseases is excluded. Prognosis The overall prognosis of this disease is poor. Intractable heart failure, fatal ventricular tachycardia and embolism of the body circulation are the most common causes of death. The disease is often clinically underdiagnosed and misdiagnosed, so it is important to pay attention to the screening and follow-up of echocardiography in patients without typical symptoms and immediate family members of patients with confirmed disease, to achieve early diagnosis and early treatment as much as possible, to avoid and reduce the emergence of LVNC complications, and to improve the prognosis of patients. VII. Treatment There is no specific treatment for this disease. The main treatment is for heart failure, arrhythmias and thromboembolism. All patients, especially those at risk of atrial fibrillation and thrombosis, should be anticoagulated with oral aspirin to prevent embolism.