Cardiomyopathy, also known as primary cardiomyopathy, refers to a group of myocardial diseases with unknown causes. It excludes specific cardiomyopathies (also called secondary cardiomyopathies) with clear disease causes or those secondary to systemic diseases, such as alcoholic cardiomyopathy caused by alcohol poisoning. Keshan disease is a unique endemic cardiomyopathy in China, characterized by distinct epidemiological and pathological changes.

Cardiomyopathy is classified into three types: dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), and restrictive cardiomyopathy (RCM). Among these, dilated and hypertrophic cardiomyopathies are the most common, while restrictive cardiomyopathy is rare in China. It mainly refers to endomyocardial fibrosis predominantly occurring in tropical regions and Lof1er eosinophilic cardiomyopathy more commonly seen in temperate zones. This article primarily discusses dilated and hypertrophic cardiomyopathies.

bubble_chart Etiology

The cause of the disease is not yet clear. Dilated cardiomyopathy may be related to certain factors such as viruses, bacteria, drug poisoning disease, and myocardial injury caused by metabolic abnormalities. Viral myocarditis is considered one of the primary causes. Hypertrophic cardiomyopathy may be associated with autosomal dominant inheritance, with about one-third having a significant family history. Abnormal catecholamine metabolism, hypertension, and high-intensity exercise can be contributing factors.

bubble_chart Pathogenesis

1. Dilated cardiomyopathy is primarily characterized by the dilation of cardiac chambers.
   1. Macroscopically, the cardiac chambers are significantly enlarged, the ventricular walls are often thinned, the myocardial trabeculae become thickened and flattened, and mural thrombi may be present. The valves and coronary arteries usually show no significant changes.
   2. Histologically, varying degrees of myocardial fibrosis are observed, along with hypertrophy and degeneration of myocardial cells.
2. Hypertrophic cardiomyopathy
   1. Macroscopically, it mainly manifests as myocardial hypertrophy, involving both the interventricular septum and the free ventricular walls. Cases without obstruction of the ventricular outflow tract are classified as hypertrophic non-obstructive cardiomyopathy; when the ratio of interventricular septal thickness to the posterior left ventricular wall thickness is ≥1.3, and the ventricular outflow tract is narrowed, it is termed hypertrophic obstructive cardiomyopathy. In obstructive cases, significant hypertrophy of the subaortic portion of the interventricular septum is also referred to as idiopathic hypertrophic subaortic stenosis (IHSS).
   2. Histologically, disorganized and bizarrely shaped hypertrophic myocardial cells can be observed.

bubble_chart Clinical Manifestations

1. Dilated Cardiomyopathy: The main features of this disease are cardiac enlargement, congestive heart failure (hence it is also called congestive cardiomyopathy), and arrhythmias.
   1. Symptoms usually develop gradually. Initially, there may only be cardiac enlargement without symptoms, and this asymptomatic period can sometimes last up to 10 years. The primary symptom is progressively worsening congestive heart failure. Early on, it may only manifest as exertional dyspnea, gradually progressing to nocturnal paroxysmal dyspnea, and eventually leading to shortness of breath, cough, and the production of white serous or pink frothy sputum even during Grade I activity or at rest. Due to reduced cardiac output, patients often experience lack of strength. Various arrhythmias are very common and, along with congestive heart failure, are often the cause of death in this disease. Because mural thrombi frequently form in this condition, thromboembolism can lead to pulmonary or systemic stirred pulse embolism, particularly in advanced stage cases. Pulmonary embolism can cause sudden severe chest pain, dyspnea, hemoptysis, and jaundice, among other symptoms. Systemic stirred pulse embolism presents with corresponding symptoms depending on the site of the embolism.
   2. Signs: (1) The cardiac borders expand bilaterally, especially prominently toward the left lower side; (2) The apical impulse shifts toward the left lower side and may exhibit a heaving impulse; (3) Auscultation findings: The first heart sound is diminished; a blowing systolic murmur may be heard over the mitral or tricuspid valve areas, caused by relative mitral or tricuspid insufficiency due to ventricular dilation—this murmur may lessen with improvement in cardiac function; The third or fourth heart sound may be audible, and a gallop rhythm may appear when the heart rate increases due to myocardial relaxation; Arrhythmias and basal lung crackles may also be detected.
2. Hypertrophic Cardiomyopathy
   1. Symptoms usually develop gradually, with onset typically before the age of 30. About one-third of cases have a family history. Non-obstructive cases may be asymptomatic or have minimal symptoms, only being detected during physical examinations or presenting as sudden death. The most common symptom is shortness of breath, caused by impaired left ventricular diastolic function, which elevates left atrial pressure and pulmonary vascular pressure, reflexively leading to tachypnea, especially after exertion. Other symptoms may include chest pain and palpitation. The severity of obstructive symptoms correlates with the degree of left ventricular outflow tract obstruction, often manifesting as cardiac or cerebral ischemia. Myocardial ischemia presents as precordial pain, typically occurring after exertion and resembling atypical colicky pain, due to the increased oxygen demand of hypertrophied myocardium during exertion while coronary stirred pulse supply is relatively insufficient. Cerebral ischemia manifests as dizziness or syncope, often occurring during activity, due to the heart rate increase further reducing the already impaired left ventricular diastolic filling, decreasing cardiac output. Additionally, sympathetic stimulation during activity or emotional stress intensifies the contraction of hypertrophied myocardium, worsening outflow tract obstruction and causing a sudden drop in cardiac output. Excessive myocardial load can lead to sudden death.
   2. Signs: (1) The apical impulse shifts toward the left lower side and exhibits a heaving impulse; (2) The cardiac dullness border expands to the left; (3) Auscultation findings: In obstructive cases, a mid- or advanced stage systolic ejection murmur may be heard at the lower left sternal border or the medial apex, radiating to the apex but not the base, possibly accompanied by a systolic tremor. Measures that increase myocardial contractility or reduce venous return can worsen outflow tract obstruction and intensify the murmur, such as administering Digitalis, isoproterenol (2μg/min), nitroglycerin, performing the Valsalva maneuver, or standing. Conversely, measures that reduce myocardial contractility, increase venous return, or raise peripheral resistance can alleviate outflow tract obstruction and weaken the murmur, such as administering beta-blockers, norepinephrine, squatting, exertion, or handgrip. Additionally, paradoxical splitting of the second heart sound may occur due to delayed closure of the aortic valve caused by obstructed left ventricular ejection.

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bubble_chart Auxiliary Examination

1. Electrocardiogram Approximately 70% of hypertrophic cardiomyopathy cases exhibit abnormal electrocardiogram (ECG) findings, making it one of the screening tests for this disease. The main manifestations include: (1) Various arrhythmias, with ectopic rhythms and atrioventricular block being the most common. (2) ST-segment depression, flattened or inverted T waves; deeply inverted T waves may sometimes resemble coronary T waves. The presence of such findings in younger patients should raise suspicion for hypertrophic cardiomyopathy. (3) Hypertrophic cardiomyopathy often presents with ventricular hypertrophy and strain, with left ventricular hypertrophy being the most common. (4) Abnormal Q waves, often a characteristic feature of hypertrophic cardiomyopathy. Large and deep Q waves may appear in left precordial leads or any limb leads, related to abnormal conduction through disorganized and fibrotic myocardium in the interventricular septum and left ventricle.
2. X-ray Examination Cardiac enlargement is observed, particularly prominent in dilated cardiomyopathy, with a cardiothoracic ratio often exceeding 0.60. In some cases of hypertrophic cardiomyopathy, the cardiac silhouette may appear nearly normal.
3. Echocardiography Echocardiography is of significant value in diagnosing cardiomyopathy, especially hypertrophic cardiomyopathy.
   1. Dilated Cardiomyopathy Echocardiography reveals the following characteristics: one "large" (marked dilation of the ventricular cavity), two "small" (reduced mitral valve opening amplitude and relatively small mitral valve compared to the dilated ventricular cavity), three "thin" (thinning of the interventricular septum and left ventricular posterior wall), and four "weak" (weakened motion of the interventricular septum and left ventricular posterior wall).
   2. Hypertrophic Cardiomyopathy Asymmetric thickening of the interventricular septum and/or left ventricular posterior wall is observed. In obstructive cases, the interventricular septum is significantly thickened, with a diastolic thickness ratio to the left ventricular posterior wall of ≥1.3:1. Systolic anterior movement (SAM phenomenon) of the mitral valve is present. The ventricular cavity is reduced, and the outflow tract is narrowed.
4. Myocardial Biopsy In dilated cardiomyopathy, compensatory hypertrophy of some cardiomyocytes is observed, interspersed with focal degeneration or necrosis, and interstitial fibrosis. These pathological changes are generally considered nonspecific. In hypertrophic cardiomyopathy, disorganized myocardial fibers and abnormally large nuclei are seen, which can confirm the diagnosis.

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bubble_chart Diagnosis

1. The diagnosis of dilated cardiomyopathy can be confirmed when there is unexplained cardiac enlargement, heart failure, arrhythmia, and characteristic changes on X-ray and echocardiography, while other organic heart diseases can be ruled out.
2. If the patient has a family history of sudden death, frequently experiences dizziness, syncope, or colicky heart pain that cannot be explained by coronary artery disease or other heart conditions, the possibility of hypertrophic cardiomyopathy should be considered. If echocardiography reveals thickening of the interventricular septum or (and) the posterior wall of the left ventricle, with a ratio ≥1.3, a reduced ventricular cavity, narrowed outflow tract, and a systolic murmur along the left sternal border—and if the murmur intensifies or diminishes with maneuvers that increase or decrease outflow tract obstruction—then the diagnosis is hypertrophic obstructive cardiomyopathy.

bubble_chart Treatment Measures

1. The cause of dilated cardiomyopathy is unknown, making prevention difficult. Treatment primarily focuses on symptomatic management of clinical manifestations.
   1. Avoid overexertion and maintain a low-salt, easily digestible diet. Patients with cardiac enlargement or decreased cardiac function should rest long-term to prevent worsening of the condition.
   2. Patients with heart failure may be treated with cardiotonic drugs, diuretics, and vasodilators. Due to the widespread myocardial damage in this disease, the efficacy and tolerance of digitalis drugs are relatively poor, and toxicity is prone to occur. Therefore, the dose must be carefully controlled and closely monitored. Diuretics and vasodilators can be used in the early stages, but in the late stage (third stage), when combined with hypotension or decreased renal function, drug doses should be adjusted under hemodynamic monitoring.
   3. Patients with rapid ventricular arrhythmias or high-grade atrioventricular block, who are at risk of sudden death, require antiarrhythmic drugs or electrical therapy.
   4. Drugs that improve myocardial metabolism, such as vitamin C, energy mixtures, cyclic adenosine monophosphate, and coenzyme Q10, can be used as adjuvant treatments.
   5. Oral anticoagulants or antiplatelet aggregation drugs may be used to prevent thromboembolic complications.
   6. Since immune mechanisms are involved in the pathogenesis of this disease, prednisone (10mg) or dexamethasone (1.5mg) can be tried, administered 3–4 times daily. After 1–2 weeks, continuation should be based on efficacy.
2. Hypertrophic cardiomyopathy
   1. Avoid overexertion, emotional agitation, and sudden exertion.
   2. Drugs that enhance myocardial contractility, such as digitalis, or those that reduce cardiac load, such as nitroglycerin, may worsen outflow tract obstruction and should be avoided whenever possible.
   3. To relieve symptoms and control arrhythmias: (1) Beta-blockers can inhibit myocardial contractility and reduce left ventricular outflow tract obstruction. Propranolol is commonly used, starting at 10mg per dose, 3–4 times daily, with gradual dose increases until symptoms improve, while ensuring heart rate and blood pressure do not drop too low. The maximum dose may reach around 200mg per day. (2) Calcium antagonists can reduce myocardial contractility, alleviate left ventricular outflow tract obstruction, and improve myocardial compliance, thereby benefiting diastolic function. Verapamil (40–120mg, 3–4 times daily) or diltiazem (30–60mg, 3 times daily) are often used with good efficacy.
   4. For rapid ventricular arrhythmias or atrial fibrillation, amiodarone is commonly prescribed. If drugs are ineffective, electrical cardioversion may be performed.
   5. For patients with a clear diagnosis and poor response to drug therapy, surgical options such as ventricular septal myotomy or partial resection of hypertrophic myocardium may be considered to alleviate symptoms.

bubble_chart Differentiation

(1) Dilated cardiomyopathy should be differentiated from the following diseases:

1. Coronary heart disease: Coronary heart disease with cardiac insufficiency is similar to dilated cardiomyopathy and requires careful differentiation. The following points aid in the diagnosis of coronary heart disease: (1) A family history of coronary heart disease is common; (2) There are often predisposing factors for coronary heart disease, such as hypertension, hyperlipidemia, smoking, etc.; (3) It is more common in the elderly; (4) There may be a history of typical colicky pain or myocardial infarction; (5) Chest X-rays often show mild or grade II enlargement of the heart shadow; (6) Electrocardiograms may show ischemic ST-T changes; (7) Echocardiography may reveal segmental abnormalities in ventricular wall motion; (8) 201Ti-myocardial imaging may show perfusion defects.
2. Pericardial effusion: Pericardial effusion with significant bilateral enlargement resembles dilated cardiomyopathy. The following points favor the diagnosis of pericardial effusion: (1) The apical impulse is weakened or absent, and the apical impulse is located within the left cardiac border; (2) Heart sounds are distant; (3) The heart shadow often appears flask-shaped and changes with body position; (4) Echocardiography shows signs of pericardial effusion; (5) Venous pressure is significantly elevated; (6) Pericardiocentesis can yield effusion.
3. Rheumatic valvular heart disease (rheumatic heart disease): When dilated cardiomyopathy causes relative mitral regurgitation, a systolic murmur may be heard at the apex, which should be differentiated from rheumatic mitral regurgitation. The key points for differentiation are: (1) The systolic murmur of rheumatic mitral regurgitation is rough and louder, and does not change or may even intensify after heart failure is controlled; the systolic murmur of dilated cardiomyopathy weakens or disappears after heart failure is controlled. (2) Rheumatic mitral regurgitation is often accompanied by mitral stenosis or aortic regurgitation, whereas dilated cardiomyopathy is not. (3) In rheumatic heart disease, certain cardiac chambers may be more significantly enlarged, whereas in dilated cardiomyopathy, all cardiac chambers are enlarged.

1. Ventricular septal defect: The location of the systolic murmur is similar to that of hypertrophic obstructive cardiomyopathy, but the systolic murmur of ventricular septal defect is pansystolic and rough, often accompanied by a systolic thrill. The murmur does not weaken or disappear with improvement in cardiac function. Patients are mostly adolescents, and two-dimensional echocardiography, cardiac catheterization, and ventriculography show signs of ventricular septal defect.
2. Aortic stenosis: The systolic murmur in this condition is located higher, most prominent at the second right intercostal space, whereas the murmur in hypertrophic obstructive cardiomyopathy is located lower, most prominent at the lower left sternal border. The former is often accompanied by a diastolic murmur (if combined with aortic regurgitation) and weakened A2, whereas the latter is not. Methods that alter myocardial contractility or peripheral resistance have little effect on the murmur of the former but affect the latter. However, the most critical differentiating point is that abnormal hypertrophy of the ventricular septum is rare in aortic stenosis, whereas it is a characteristic feature of hypertrophic cardiomyopathy.
3. Coronary heart disease: Refer to "Differential Diagnosis of Dilated Cardiomyopathy."