I. Brief description of the disease
This type is characterized by enlargement of the left or right ventricle or bilateral ventricles with myocardial hypertrophy. The ventricular systolic function is reduced with or without congestive heart failure. Ventricular or atrial arrhythmias are common. The disease is progressive and death can occur at any stage of the disease
Etiology
The etiology of the disease is unknown to date, but it has been found to be associated with the following factors.
1, the etiology of infection
In animal experiments, coxsackievirus and cerebral myocarditis virus can not only cause viral myocarditis, but also cause lesions similar to dilated cardiomyopathy, and the chance of transformation into dilated cardiomyopathy in patients with acute viral myocarditis was found to be significantly greater than in the general population during long-term follow-up. Many patients with this disease have higher titers of coxsackievirus B neutralizing antibody in their blood than normal people; in recent years, RNA of enterovirus or cytomegalovirus has been found in myocardial biopsy specimens from patients with this disease by molecular biology techniques, all of which indicate that this disease is closely related to viral myocarditis and that this disease is likely to be a persistent infection.
2, genetic and autoimmune
It was found that the disease is related to histocompatibility antigens. Compared with non-patients with the disease, there is an increase in HLAB27, HLAA2, HLADR4, HLADQ4 loci and a decrease in HLADRw6 loci in the disease. The change in HLA is related to autosomal recessive inheritance, which can explain the familial tendency of some patients with the disease. On the other hand, there can be altered immune response, increased susceptibility to viral infection, leading to myocardial autoimmune damage.
3. Cellular immunity
In patients with this disease, the activity of natural killer cells is reduced, weakening the body’s defensive capacity, and the number and function of suppressor T lymphocytes are reduced, resulting in a cell-mediated immune response that causes vascular and myocardial injury.
In summary, it is thought that the possible pathogenesis of the disease may be that the coxsackievirus encroaches on the myocardium, proliferates in the myocardium and causes myocardial cell necrosis; in the second stage, the virus cannot be found in the myocardium, but there is an increase in lymphocytes, which sensitize the myocardial cells and cause an immune response and myocardial cell necrosis; in the later stage, the inflammatory cell infiltrate decreases or disappears and becomes fibrotic, which intermingles with hypertrophic or reduced The inflammatory cell infiltration decreases or disappears and becomes fibrotic, intertwined with hypertrophic or reduced cardiomyocytes, constituting the lesion of dilated cardiomyopathy. Although the theory of viral infection and immune response is the main pathogenesis, there are still many problems that remain to be clarified and need further study.
Third, the pathological changes
The weight of the heart increases and is approximately double the normal weight. The chambers of the heart are enlarged and the myocardium is gray and flaccid. Although the ventricular wall myocardium is hypertrophied, the thickness of the ventricular wall is still nearly normal because of the enlarged chambers. The endocardium may also be thickened. Intracavitary wall thrombus formation is not uncommon. Myocardial fibrosis is common and is focally distributed on the inner edge of the ventricular wall, or the wall may be damaged in patches.
Microscopic examination of the heart in this disease lacks specific findings. Myocardial fibers may be seen to be hypertrophied, with nuclei that are fixed, deformed, or absent and intracytoplasmic vacuole formation. There is an increase in fibrous tissue, either due to an increase in interstitial collagen tissue or due to focal myocardial fibers being replaced by fibrous tissue. Myocardial fibers may be divided by striated fibrous tissue. Collagen and elastic fibers are also increased in the endocardium. Degenerative changes of varying degrees can be seen, mostly cardiomyocyte lysis, especially in cases with long duration of disease.
Electron microscopy reveals swollen mitochondria with broken or absent cristae in cardiomyocytes; enlarged interstitial spaces in the sarcoplasmic membrane with fibrous material and granular lipofuscin; myogenic fibers may disappear.
Myocardial lesions reduce the contractility of the heart. The early left ventricular isovolumic systole period slows down the rate of pressure rise in the left ventricle and the rate of blood ejection. At this time, the reduction in heart beat volume is compensated by accelerated heart rate, and the cardiac output can still be maintained. Later, the left ventricle is not emptied, there is residual blood volume, the end-diastolic pressure increases, and gradually develops left heart failure. The left atrial and pulmonary artery pressures increase one after another over time, and finally right heart failure develops. In a few cases, the lesion is predominantly right ventricular, and right heart failure develops. The dilatation of the ventricle enlarges the atrioventricular valve annulus, resulting in mitral or tricuspid valve closure insufficiency. The dilated heart chambers, increased tension within the ventricular wall, increased oxygen consumption, myocardial hypertrophy, and accelerated heart rate cause relative myocardial ischemia, while the myocardial capacity to take up oxygen has reached its limit, thus causing angina pectoris. Myocardial lesions involving the pacing and conduction system can cause various arrhythmias.
Clinical manifestations
The disease can develop at all ages, but middle-aged people are the most common. The onset of the disease is slow, and the initial examination reveals an enlarged heart with compensated cardiac function without conscious discomfort. After a period of time, symptoms gradually appear, and this period can sometimes be more than 10 years. The symptoms are mainly congestive heart failure, with shortness of breath and swelling being the most common. The shortness of breath initially occurs after labor or exertion, and later also during light activity or rest, or with nocturnal paroxysmal shortness of breath. Due to low cardiac output, patients often feel weak. On physical examination, the heart rate is accelerated, the apical beats are shifted to the lower left, there may be elevated beats, the turbinate is enlarged to the left, a third or fourth tone can often be heard, and the heart rate is in gallop rhythm when it is fast. Due to the enlargement of the heart chambers, there may be a systolic blowing murmur due to relative mitral or tricuspid valve insufficiency, which decreases when cardiac function improves. Blood pressure is mostly normal, but in advanced cases blood pressure decreases, pulse pressure is small, and diastolic pressure may be mildly elevated in the presence of heart failure. The presence of alternating pulses indicates left heart failure. The pulse is often weak. A rhotic sound may be present at the base of the second pulse in heart failure. In right heart failure, the liver is enlarged, and edema begins in the lower extremities. Hydrothorax and ascites are not uncommon in patients with advanced disease. A variety of arrhythmias can be present, and they are the first or main manifestation, and multiple arrhythmias can be combined to form a more complex rhythm, which can be recurrent and sometimes very persistent. High atrioventricular block, ventricular fibrillation, sinus block or pause can lead to A.S. syndrome, which is one of the causes of death. In addition, there may be embolism in the brain, kidney, lung, etc.
V. Diagnosis
In 1980, the World Health Organization pointed out that this disease is unexplained left ventricular or biventricular enlargement, impaired ventricular systolic function, with or without congestive heart failure and arrhythmia, and other causes must be excluded before the diagnosis of this disease can be made.
In 1995, the Chinese Society of Cardiovascular Diseases organized a symposium and proposed the following reference criteria for the diagnosis of this disease.
1, clinical manifestations of cardiac enlargement, reduced ventricular systolic function with or without congestive heart failure, often with arrhythmias, can occur embolism and sudden death and other complications.
2, heart enlargement X-ray examination cardiothoracic ratio> 0.5, echocardiography shows the whole heart enlargement, especially the left ventricle enlargement is obvious, the left ventricular end-diastolic internal diameter ≥ 2.7cm/m2, the heart may be spherical.
3, ventricular systolic function is reduced echocardiographic detection of diffuse reduction of ventricular wall motion, ejection fraction is less than normal values.
4. Other specific (secondary) cardiomyopathies and endemic cardiomyopathies (Keshan disease) must be excluded, including ischemic cardiomyopathy, perinatal cardiomyopathy, alcoholic cardiomyopathy, cardiomyopathies due to metabolic and endocrine disorders such as hyperthyroidism, hypothyroidism, amyloidosis, diabetes mellitus, cardiomyopathies due to genetic familial neuromuscular disorders, systemic systemic diseases such as systemic Idiopathic dilated cardiomyopathy can be diagnosed only when it is caused by systemic diseases such as systemic lupus erythematosus, rheumatoid arthritis, and toxic cardiomyopathy.
If available, anti-cardiac peptide antibodies such as anti-cardiac mitochondrial ADP/ATP carrier antibodies, anti-myosin antibodies, anti-β1-receptor antibodies, and anti-M2 cholinergic receptor antibodies can be detected in the patient’s serum as an aid to the diagnosis of this disease. Coronary angiography is required for those who are clinically difficult to differentiate from coronary artery disease.
Endomyocardial biopsy: Pathological examination is not specific for the diagnosis of this disease, but it helps in the differential diagnosis with atopic cardiomyopathy and acute myocarditis. Multimerase chain reaction (PCR) or in situ hybridization with endomyocardial biopsy specimens can help in the diagnosis of the etiology of infection; or genetic analysis for specific cellular abnormalities.
(A) Rheumatic heart disease
Cardiomyopathy may also have a systolic murmur in the mitral or tricuspid region, but it is usually not accompanied by a diastolic murmur, and is louder in heart failure and decreases or disappears when heart failure is controlled, as opposed to rheumatic heart disease. In cardiomyopathy there is often simultaneous enlargement of multiple heart chambers, as opposed to rheumatic heart disease in which the left atrium, left ventricle or right ventricle predominates. Ultrasonography helps to differentiate.
(b) Pericardial effusion cardiomyopathy
The enlarged heart and weakened heartbeat must be distinguished from pericardial effusion. In cardiomyopathy, the apical pulsation is shifted to the lower left and corresponds to the left outer edge of the cloudy heart border, while in pericardial effusion, the apical pulsation is often inconspicuous or medial to the left outer edge of the cloudy heart border. Systolic murmurs in the mitral or tricuspid region, ventricular hypertrophy on the electrocardiogram, abnormal Q waves, and various complex arrhythmias are indicative of cardiomyopathy. It is not difficult to distinguish the two on ultrasound. Multiple flat segments or dark areas of fluid in the pericardium indicate pericardial effusion, while an enlarged heart is indicative of cardiomyopathy. It is important to note that a small amount of pericardial fluid can also be present in cardiomyopathy, but it is neither sufficient to cause cardiac compression nor to affect cardiac signs and cardiac function, and is only an ultrasound finding. The systolic time interval is significantly abnormal in cardiomyopathy and normal in pericardial disease.
(iii) Hypertensive heart disease cardiomyopathy
Transient hypertension may be present, but diastolic blood pressure mostly does not exceed 14.67 kPa (110 mmHg) and appears in acute heart failure, and blood pressure decreases after heart failure improves. Unlike hypertensive heart disease, fundus, urinary routine and renal function are normal.
(iv) Coronary heart disease
In middle-aged patients or older, coronary artery disease and cardiomyopathy must be considered if there is cardiac enlargement, arrhythmia or heart failure without other causes. Those with susceptibility factors such as hypertension, hyperlipidemia or diabetes mellitus, and those with segmental abnormalities in ventricular wall activity are conducive to the diagnosis of coronary artery disease. In recent years, coronary artery lesions cause extensive long-term ischemia and fibrosis of the heart, the development of cardiac insufficiency is called “ischemic cardiomyopathy”, if there is no angina or myocardial infarction in the past, it is difficult to distinguish from cardiomyopathy, and then cardiomyopathy can also have pathological Q waves and angina, then the differentiation must rely on coronary angiography.
(E) Congenital heart disease
Most of them have obvious signs and are not difficult to distinguish. In tricuspid valve subluxation malformation, there are murmurs in the tricuspid region, and there may be gallop rhythm, weakened heartbeat, right heart enlargement and failure, which must be distinguished from cardiomyopathy, but the symptoms of this disease appear in early life, the left ventricle is not large, and cyanosis is more prominent. Echocardiography can clarify the diagnosis.
(vi) Secondary cardiomyopathy
Systemic diseases such as systemic lupus erythematosus, scleroderma, hemochromatosis, amyloidosis, glycogen accumulation disorder, neuromuscular diseases, etc. have their primary manifestations for differentiation. More important is the distinction between myocarditis and myocarditis. Acute myocarditis often occurs at the time of viral infection or shortly thereafter and is not very difficult to distinguish. In fact, many dilated cardiomyopathies develop from myocarditis, which is called “post-myocarditis cardiomyopathy”.
In recent years, endomyocardial myocardial biopsy has been carried out clinically, and specimens are obtained from cardiac catheters with biopsy forceps for pathological and viral examination, which can reveal evidence of myocardial inflammation, but there are still some problems to be solved in terms of diagnostic criteria for pathological histology and removal of artifacts.
X-rays show an enlarged cardiac shadow with a spherical appearance in advanced stages, indicating that all chambers of the heart are enlarged and the appearance is rather like a pericardial effusion. In a few patients, enlargement of the left ventricle, left atrium, or right ventricle is predominant, with an appearance similar to mitral valve lesions. Fluoroscopy reveals a weaker than normal heartbeat. The aorta is usually not enlarged. Pulmonary stasis and interstitial edema are often present in patients with more advanced disease, and there may be septal lines at the diaphragmatic angle of the ribs of both lungs.
The electrocardiogram is almost always abnormal in symptomatic patients, and many asymptomatic patients have electrocardiogram changes, with changes dominated by cardiac hypertrophy, myocardial damage and arrhythmias. Left ventricular hypertrophy is common, often combined with myocardial strain, and right ventricular hypertrophy is often present in advanced stages; left or right atrial hypertrophy may also be present. Myocardial damage is common, with ST-segment depression, flat or biphasic or inverted T waves as the main manifestation, and sometimes T waves show ischemic changes. A few patients may have pathological Q waves, similar to myocardial infarction, which are mostly located in the anterior septum (V1 and V2 leads), probably as a result of septal fibrosis. Intraventricular conduction block is common and can occur in both left and right bundle branches or in branches of the left bundle branch. Arrhythmias are common, especially in the later stages, and are dominated by ectopic rhythm and conduction block. Ectopic rhythms may arise from the atria, atrioventricular junction, or ventricles, and may evolve from premature beats to tachycardia, to flutter or fibrillation, or from sinus lesions, atrioventricular junction escape or escape rhythms, or ventricular rhythms themselves. First- to third-degree atrioventricular block can occur.
In the early stages of the disease, mild enlargement of the heart chambers is seen on echocardiography, especially in the left ventricle, and wall motion is reduced. The anterior mitral leaflet bifurcation may disappear, while the anterior and posterior leaflets show anisotropic activity. The left ventricular ejection ratio is often reduced to less than 50%, and the myocardial shortening ratio is also reduced. There may be a small amount of pericardial effusion.
Nuclear ventriculography may also show enlarged chambers and reduced wall motion, with a reduced left ventricular ejection fraction, more pronounced after exercise.
The systolic time interval may be abnormal early, with a shortened LVET and a prolonged pre-ejection period (PEP) and increased PEP/LVET.
Early cardiac catheterization is nearly normal, and right and left ventricular end-diastolic pressures may be slightly increased. In the presence of heart failure, the cardiac expulsion index is reduced, the arteriovenous oxygen difference is large, and pulmonary artery and atrial pressures are increased. Cardiac angiography shows enlarged heart chambers and reduced ventricular wall motion.
VI. Treatment
(a) Treatment principles.
1, general treatment: rest, sedation if necessary, low salt diet in heart failure.
2, prevention and control of arrhythmias and cardiac insufficiency.
3. anticoagulation therapy for those with a history of embolism.
4, with a large amount of pleural effusion, thoracentesis for fluid extraction.
5.Severe patients may consider artificial heart surgery or heart transplantation.
6, symptomatic, supportive treatment.
Prevention is difficult because the cause of the disease is not known. It is of practical significance to pay attention to cardiac changes at the time of viral infection and treat them early.
Treatment is mainly aimed at clinical manifestations
1.Rest and avoidance of exertion must be very emphasized, such as those with enlarged heart and decompensated heart function should pay more attention, and long-term rest is desirable to avoid deterioration of the condition.
2, there is heart failure treatment principle is the same as general heart failure, the use of cardiac drugs, diuretics and vasodilators, due to the more extensive myocardial damage, detailed Diosmin class, diuretics beneficial, in low glomerular filtration, hydrochlorothiazide may fail, at this time, the need to use tab diuretics, such as: furosemide. Vasodilators, such as angiotensin-converting enzyme inhibitors, are also useful, but they should be used in small doses to avoid hypotension.
In recent years, it has been found that this disease is effective with beta-blockers when there is heart failure. The mechanism may be that the adrenergic nerves are overexcited in chronic heart failure and beta receptor density is downregulated, in this disease its degree is greater than after myocardial infarction, beta receptor density is downregulated, in this disease its degree is greater than after myocardial infarction, after using beta-blockers the harmful effects of adrenergic nerve overexcitation are removed and beta receptor density in the myocardium is Up-regulation, known to have β1 good, starting with a very small agent, and then slowly increase the dose, such treatment can prolong the life of patients.
3, with arrhythmias, especially in symptomatic people need to be treated with antiarrhythmic drugs or electrical methods, the treatment of rapid ventricular rhythm with high atrioventricular block and the risk of sudden death should be active.
4.For the prevention of embolic complications, oral anticoagulants or anti-platelet aggregation drugs are available.
5, improve the myocardial metabolism of drugs such as vitamin C, adenosine triphosphate, coenzyme A, cyclized adenosine acid, coenzyme Q10, etc. can be used as adjuvant therapy.
6, for long-term heart failure, medical treatment is ineffective, should be considered for heart transplantation, postoperative active control of infection, improve immunosuppression, correct rejection, survival rate after 1 year up to 85% or more.
(B) the principles of medication.
1, cardiomyopathy when sensitive to digitalis drugs, the application of a smaller dose is appropriate, and pay attention to toxic reactions, or the use of non-cardiac glycoside positive inotropic drugs.
2, during the application of diuretics must pay attention to electrolyte balance.
3, there is the use of heart rate suppressing drugs or electrical conversion of tachyarrhythmias, should be alert to the possibility of the simultaneous presence of sick sinus syndrome.
4.A permanent artificial pacemaker can be installed for those with combined chronic complete atrioventricular block and sick sinus syndrome.
5, during the application of antiarrhythmic drugs, the electrocardiogram should be reviewed regularly.
6. During the use of anticoagulant drugs, attention should be paid to bleeding manifestations and regular rechecking of bleeding and clotting time and prothrombin time.
VII. Prognosis
The duration of this type of disease varies, with short cases dying within 1 year after the onset of the disease and long cases surviving for more than 20 years. The prognosis is not good for those with significant heart enlargement, persistent heart failure or persistent arrhythmias. Many patients may have sudden death.
Eight, prevention of common sense
Patients diagnosed with dilated cardiomyopathy should maintain a good state of mind, avoid exertion, supplement nutrition, pay attention to the prevention of respiratory tract infections, stop smoking and drinking, and regularly review at the hospital to protect or improve cardiac function and improve the quality of life. If you experience panic, shortness of breath, chest discomfort, or weakness, you should go to the hospital promptly. Female patients should not be pregnant. Once cardiac insufficiency occurs, longer rest and low-salt diet should be given. If severe dyspnea occurs, which is aggravated when lying down and sweating profusely, it may be a severe cardiac insufficiency. The patient should be put in a sitting or semi-sitting position and called for help from the medical emergency center or sent to a nearby hospital by the safest, smoothest and fastest transportation.