Dilated cardiomyopathy (DCM), also known as congestive cardiomyopathy (CCM), is the most common form of cardiomyopathy. There is enlargement of the heart, systolic insufficiency, and the occurrence of heart failure, etc. It is an unexplained cardiomyopathy of one or both sides caused by primary cardiac disease. The etiology of the disease remains unclear in most cases and may be related to genetic, toxic, metabolic (e.g. carnitine deficiency) and nutritional disorders (e.g. selenium deficiency) factors. In recent years, it is believed that viral persistence of infection in subclinical or occult viral myocarditis and virus-mediated humoral and cellular immune responses cause or induce dilated cardiomyopathy. Analysis of the etiology of DCM in adults: 47% with unknown etiology, 12% with myocarditis, 11% with coronary artery disease, and 30% with other etiologies. Children of all ages can be affected. Most of them have a slow onset and mainly present with chronic congestive heart failure, occasionally with sudden onset of acute heart failure or arrhythmias. Older children present with weakness, poor appetite, inactivity, abdominal pain, dyspnea and marked tachycardia after activity, hypuria, and edema. Infants have difficulty feeding, do not gain weight, have difficulty breathing while suckling, sweating, restlessness, and reduced food intake.
Syncope or presyncope occurs in about 10% of children. The patient’s face is pale, breathing and heart rate are accelerated, pulse is weak, and blood pressure is normal or low. The precordial region is dilated, the apical beat is shifted to the left, the heart border is enlarged to the left, and the first heart sound is diminished, often with a galloping rhythm. Due to the enlargement of the heart chambers, functional mitral valve closure insufficiency occurs, and a mild to moderate blowing systolic murmur is present in the apical region. The enlarged left atrium may compress the left main bronchus and cause left lower lung atelectasis, so the left lower dorsal breath sounds are reduced.
I. Examination
1. Chest X-ray: The chest X-ray shows moderate to severe general enlargement of the heart shadow, with left ventricular enlargement as the main feature and weakened heartbeat. The heart beat is weakened under fluoroscopy. In heart failure, pulmonary stasis or pulmonary edema can be seen, and sometimes pleural effusion and left lower lung atelectasis can be seen.
2. Electrocardiogram: The electrocardiogram shows myocardial damage, arrhythmia and ventricular hypertrophy as the main changes. Sinus tachycardia, left ventricular hypertrophy and ST-T changes are most common. Atrial hypertrophy, right ventricular hypertrophy and abnormal Q waves may also be present. First-degree AV block, bundle branch block and ventricular asystole are the most common arrhythmias. About half of the patients have ventricular and supraventricular arrhythmias on ambulatory ECG monitoring.
(1) ST-T changes: ST-segment reduction is mostly horizontal, with inverted or low flat T waves.
(2) Ectopic beats and ectopic rhythm: ventricular or atrial precontractions are the most common. It may show frequent, polymorphic, and multi-source ventricular asystole. It may develop into ventricular tachycardia or ventricular fibrillation.
(3) Conduction disturbances: Atrioventricular block (first to third degree), intraventricular, bundle branch and branch block are seen in some cases.
(4) Ventricular hypertrophy: left ventricular hypertrophy of varying degrees is seen in some cases, while right ventricular hypertrophy or bilateral ventricular hypertrophy is uncommon.
(3) Echocardiography: each ventricular cavity is obviously enlarged, mainly in the left ventricle; septum and posterior left ventricular wall motion is reduced, anterior and posterior mitral valve leaflets open less; left ventricular systolic dysfunction (decreased ejection fraction and shortening rate of short axis), posterior left ventricular wall and septum motion is reduced, ejection fraction and shortening fraction are significantly decreased.
II. Treatment
There is no specific therapeutic measure, let alone the establishment of primary prevention of the disease; early detection, early diagnosis and early treatment should be emphasized; the main measures include controlling heart failure, reversing myocardial hypertrophy and preventing ventricular remodeling. Long-term regular anti-heart failure treatment may be beneficial to the improvement of prognosis.
1.General treatment
(1) Prevention and control of infection: upper respiratory tract infection can induce or aggravate heart failure in DCM. Some scholars suggest using human gammaglobulin or transfer factor as appropriate in susceptible and high-risk DCM patients to enhance the body’s immunity and prevent respiratory tract infection. Once infected, antibiotics should be used promptly.
(2) Diet: Patients with DCM heart failure should limit sodium and control water appropriately, with sodium intake of 2-5 g in mild heart failure, 1.0-2.5 g in moderate heart failure, and 0.5-1.0 g in severe heart failure. diet should be high in protein, high in vitamins and rich in nutrients, easy to digest, and avoid stimulating foods. Increasing the content of linoleic acid in the diet may have a certain impact on the prognosis of DCM; selenium supplementation therapy may lead to upregulation of myocardial β-receptor function, which is beneficial to the improvement of heart failure in DCM.
(3) Rest: Ensure adequate sleep, avoid strenuous exercise and excessive fatigue. Bed rest for heart failure to reduce cardiac load.
(4) Oxygenation: Intermittent oxygenation can improve the oxygen supply of the child, which is beneficial to the recovery of heart failure. Low-flow oxygen can be administered by nasal cannula.
2. Etiology and symptomatic treatment
If there is a clear cause, the cause should be eliminated first, such as drugs or alcohol poisoning, and symptomatic treatment should be given. If the cause is unknown or not eliminated, heart failure should be controlled. For severe heart failure, intravenous positive inotropic drugs, such as catecholamines or phosphodiesterase inhibitors, which also have a vasodilating effect, should be administered first. Sodium nitroprusside can also be added to reduce ventricular afterload, but blood pressure changes should be closely monitored. In severe edema or pulmonary edema, strong diuretics should be given intravenously and electrolytes should be monitored. After the condition stabilizes, long-term captopril or enalapril, digoxin and diuretics should be given. If conventional anti-heart failure treatment is not effective, beta blocker metoprolol may be added with caution. Drugs to improve myocardial metabolism such as pan-decolone (coenzyme Q10) can also be used.
3.Immunosuppression
There are still different opinions on the application of immunosuppressive drugs.
4.Treatment of complications
Amiodarone is used for complications of ventricular arrhythmias. Thrombolytic therapy should be applied in case of embolism.
5.Surgical treatment
In addition to medical treatment, acute severe heart failure needs to be resuscitated with mechanical devices that assist ventricular function outside the body, such as intra-aortic balloon counterpulsation and cardiopulmonary machines for assisted circulation. In a small number of patients, the condition deteriorates even after treatment, and eventually heart transplantation is required.
III. Prognosis
The prognosis of pediatric DCM is poor, with rapid deterioration and most dying of severe heart failure within 6 months to 1 year after onset, and a small number of sudden death due to ventricular arrhythmias. 5-year survival rate is about 60%. In category 2, cardiac function improves but does not return to normal, and there is still a risk of sudden death; in category 3, cardiac function does not improve or deteriorates further, and death usually occurs early in the course of the disease due to severe heart failure. Other indications of poor prognosis are severe cardiac enlargement, cardiothoracic ratio ≥ 0.65, ejection fraction < 0.20, embolic phenomena and ventricular arrhythmias. The prognosis has improved in recent years due to improved treatment and improved heart transplantation survival rates.
There is no definite preventive measure, but we should actively prevent and treat viral myocarditis; balance diet and strengthen nutrition, especially to prevent selenium deficiency, linoleic acid deficiency, potassium and magnesium deficiency, which can cause myocardial damage.