Pediatric hypertrophic cardiomyopathy

Introduction to pediatric hypertrophic cardiomyopathy Hypertrophic cardiomyopathy (HCM) is a hereditary disease characterized by ventricular hypertrophy and no enlargement of the heart chamber. HCM is also called idiopathic subaortic stenosis (ISS) and asymmetry ventricular septal hypertrophy. (Asym-metricseptalhypertrophy, ASH), a variety of clinical manifestations, is one of the causes of sudden death in older children and adolescents. Pediatric hypertrophic cardiomyopathy includes a group of diseases of different etiology, characterized by abnormal unexplained ventricular hypertrophy and heart The cavity is not enlarged, mainly left heart involvement, right ventricular myocardium can also be affected, ventricular hypertrophy is asymmetrical, uneven, ventricular cavity is small, left ventricular blood filling is blocked, left ventricular diastolic compliance decline is basic pathological, tissue Learned to present a group of myocardial diseases with disordered myocardial fibers. HCM was first described by Liouville and Hallopeau in 1869. basic knowledge The proportion of sickness: 0.0001% - 0.0002% Susceptible people: children Mode of infection: non-infectious Complications: arrhythmia, heart failure, sudden death

Causes of pediatric hypertrophic cardiomyopathy

It has been confirmed that HCM is an autosomal dominant genetic disease, 50% of the siblings' siblings are involved, and about 50% of HCM is caused by mutations in seven coding contractile proteins, in which the myosin heavy chain gene mutation accounts for 30%. 40%, although HCM relatives caused by the same gene mutation often have significantly different clinical manifestations, several studies have shown that the phenotype of HCM is mainly determined by genetic defects, such as specific morphological changes and sudden death. Associated with a genetic mutation.

Genetic factors (45%):

Primary hypertrophic cardiomyopathy may be familial or sporadic. According to epidemiological findings, 2/3 of those with a family history account for 1/3 of familial morbidity. 50% of HCM causes are not It is clear that 50% of families have genetic mutations that are most commonly found in autosomal dominant inheritance, accounting for about 76%.

Calcium regulation disorder (28%):

Clinical studies and experiments have shown that patients with hypertrophic cardiomyopathy have calcium regulation disorders, especially elevated myocardial intracellular calcium levels are associated with ventricular diastolic function. Wagner et al found that the number of calcium ion receptors in cardiomyocytes increased in patients with hypertrophic cardiomyopathy, reflecting the increase in voltage-dependent calcium channel density. This phenomenon exists not only in hypertrophic ventricular septum but also in normal right atrial myocardium. The increase in body is not a secondary change, but a primary defect.

Prevention of hypertrophic cardiomyopathy in children

Pay attention to genetic counseling, and other measures are subject to further research on etiology. Hypertrophic cardiomyopathy has a family genetic predisposition, so family history of the disease should pay attention to regular hospital visits. If there is shortness of breath, fatigue, pain in the precordial area, or syncope, it is advisable to go to the hospital as soon as possible. For patients diagnosed with hypertrophic cardiomyopathy, it is advisable to avoid fatigue, prevent respiratory infections, quit smoking and alcohol, maintain a good state of mind, and regularly go to the hospital for review to protect or improve heart function and improve quality of life.

Complications of pediatric hypertrophic cardiomyopathy Complications, arrhythmia, heart failure, sudden death

Often complicated by heart failure, arrhythmia, prone to sudden death.

Symptoms of pediatric hypertrophic cardiomyopathy Common symptoms Weak dyspnea heart murmur Myocardium hypertrophy Dizziness angina pectoris palpitations and nail bed slightly blue-green heart enlargement

Children with HCM have no obvious symptoms, often seeing for the first time due to heart murmur or HCM patients in the family. The clinical manifestations are variability and vary according to the age of onset. Infants under 1 year old are more severe than children over 1 year old, and 60% of infants have HCM. Left and right ventricular outflow obstruction, heart failure often occurs, death within 1 year old, children over 1 year old are usually asymptomatic, only a few left ventricular outflow tract obstruction, but more likely to sudden death than infants.

Common symptoms of infants are difficulty breathing, tachycardia, difficulty feeding, heart failure in severe cases, cyanosis, enlarged heart, heart murmur or arrhythmia, and a small number of children have accelerated breathing, fatigue, palpitations, angina, dizziness, syncope And fainting, and sudden death after the activity, even if there is no obvious symptoms, there is a risk of sudden death, heart failure is rare, signs of short pulse, apical beats are lifted or double pulsation, the first heart sound is normal, the second heart sounds most Normal, a small number of left ventricular outflow tract obstruction, abnormal division, 3/6 systolic jet murmur at the lower left sternal border and apex of the sternum, immediately strengthened after exercise, and the squat position was weakened.

Examination of pediatric hypertrophic cardiomyopathy

1. General blood test: mainly to screen for metabolic diseases that can cause cardiac hypertrophy, such as checking fasting blood sugar, blood carnitine, lactate, pyruvic acid, amino acid concentration, etc.; checking urine amino acids, organic acids and other ingredients and Its content.

2. Endomyocardial biopsy: consider cardiac catheterization and cardiovascular angiography when considering surgical treatment, measurement of hemodynamic parameters, pressure gradient, ventricular hypertrophy and extent, cardiac cavity deformation, outflow tract stenosis and valvular regurgitation In other cases, a small number of infant HCM need to do a myocardial biopsy to exclude Pompe disease (type II glycogen storage disease), but the latter skeletal muscle biopsy can be determined, and safe, hypertrophic myocardial fiber arrangement disorder, myocardial cells are abnormally large, nuclear circumference Often surrounded by "halo", mitochondrial hyperplasia, histochemical determination of severe glycogen accumulation, immunochemical assays showed increased catecholamine content in hypertrophic myocardium, with diagnostic significance, 3. Genetic investigation for family history, and genetic mutations, And help determine the prognosis and guide treatment.

3. ECG examination: can show left ventricular hypertrophy, ST segment decline, T wave inversion, left atrial hypertrophy, abnormal Q wave, QT interval prolonged, a few pre-excitation syndrome or other indoor block diagram, infant patients often have Right ventricular hypertrophy may reflect right ventricular outflow obstruction. Dynamic electrocardiographic monitoring shows ventricular premature contraction, ventricular and supraventricular tachycardia, sinus bradycardia and atrioventricular block, and a few children have normal ECG. However, most children have abnormal electrocardiograms:

(1) left ventricular hypertrophy.

(2) Abnormal Q wave (30% to 50%): deep, narrow and persistent, more common in I, II, III, aVF, aVL or V4, V5 lead, pathological Q wave formation, on the one hand The initial vector of hypertrophic septal depolarization is related to the forward and upward movement, resulting in II, III, avF being abnormal Q waves, right chest lead being high and narrow R waves; on the other hand, myocardial fibrosis, degeneration and disordering, call power reduction Or disappeared, so that the interventricular septum is added to the right front depolarization vector, causing an abnormal Q wave in the left chest lead.

(3) ST-T changes: It can be seen that the huge T wave centered on V3 and V4 is inverted, and most of the chest lead in IHSS children have no deep inverted T waves, and even shallow inverted T waves are rare.

(4) arrhythmia: common pre-excitation syndrome, complete atrioventricular block, bundle branch block and rapid ventricular arrhythmia, etc., also seen sinus node lesions, supraventricular tachycardia, etc. HCM caused by glycogen storage disease (Pompe disease) has a typical triad of electrocardiogram: short PR interval, abnormally high QRS complex and extensive T wave inversion. Heart rate variability (HRV) examination does not help The detection of HCM patients with high-risk sudden death; QTc dispersion measurement showed that the QTc dispersion of HCM patients was significantly higher, and the QTc dispersion of obstructive type was significantly higher than that of non-obstructive type. The QTc dispersion was significantly positively correlated with the degree of ventricular septal hypertrophy. The QTc dispersion was HCM with ventricular arrhythmia and predictors of sudden death.

4. Echocardiography: Echocardiography is more meaningful for the diagnosis of HCM. It is the diagnostic method for HCM. Normal infants have a septal thickness of 4 mm, preschool children 5 mm, older children 7 mm, left ventricular posterior wall and chamber. With equal thickness, Doppler echocardiography can detect the following changes:

(1) ventricular septum: asymmetry hypertrophy of the interventricular septum, poor mobility, small cardiac chamber, narrowing of the left ventricular systolic diameter, ratio of ventricular septum to left ventricular posterior wall thickness (IVS/LVPW) of 1.3 to 1.5, ventricle Wall thickening can invade different parts: the anterior septum accounts for 10% to 15%, the anterior septum and posterior septum account for 20% to 35%, the posterior septum, the apex or anterior wall accounts for about 20%, the anterior wall and Room spacing accounts for 50%.

(2) left ventricular outflow obstruction and pressure gradient: left ventricular outflow tract stenosis, aortic and left ventricular outflow tract pressure step can reach 9.3kPa (70mmHg) or more.

(3) SAM phenomenon: systolic anterior motion of the anterior mitral leaflet (SAM) phenomenon, in contact with hypertrophic ventricular septum, SAM phenomenon begins at the end of the first 1/3 of the systole, At 1/3 of the systolic phase, the ventricular septal contact is formed, and the left ventricular outflow tract stenosis is formed. The diastolic anterior mitral anterior lobe and the ventricular septal distance are smaller than normal. The SAM phenomenon may be related to myocardial ischemia or myocardial infarction, microvascular disease, Cardiac oxygen supply and demand imbalance, wall motion disorder and myocardial degeneration fibrosis.

(4) aortic valve: aortic valve systolic flutter, closed early in the systole, in a semi-occlusive state, isovolumic diastolic time prolonged, some patients may have aortic regurgitation.

(5) Changes in cardiac function: decreased left ventricular ejection fraction; ventricular diastolic dysfunction, prolonged ventricular diastolic blood flow E peak acceleration time prolonged, early diastolic E peak decreased, E peak deceleration DEF significantly decreased, late diastolic A peak Increased repayment.

5. Cardiac catheter: Diagnosis of HCM with echocardiography can replace cardiac catheterization. Cardiac catheterization and cardiovascular angiography should be performed when considering surgical treatment. Hemodynamic parameters, pressure gradient, ventricular hypertrophy and extent, cardiac chamber deformation, outflow tract stenosis and valvular regurgitation should be measured. A small number of infant HCMs require a myocardial biopsy to exclude Pompe disease (type II glycogen storage disease), but the latter skeletal muscle biopsy can be determined and safe. The left ventricular and left ventricular outflow tract systolic pressure difference > 2.67 kPa (20 mmHg), left ventricular end-diastolic pressure increased, left ventricular angiography showed a narrowing of the heart chamber, "S"-shaped stenosis under the aortic valve, ventricular wall thickening Irregular thickening of the interventricular septum protrudes into the heart chamber, and the left atrium can also be simultaneously developed. The left ventricular angiography of the apex of the apex can show a "vessel-like" change, and the right ventricular hypertrophic HCM requires right ventricular angiography.

6. Chest X-ray examination: X-ray examination is non-specific, normal pulmonary blood or mild pulmonary congestion, normal heart size or mild left ventricular enlargement, infants with more heart enlargement, and increased lung texture, pulmonary congestion.

7. Magnetic Resonance Imaging: Provides more detailed morphological data to detect regional left ventricular asynchrony motion in HCM patients with normal global contraction, which is more valuable for analyzing the fuzzy results produced by left ventricular filling indicators.

8. Radionuclide examination: visible left ventricular diastolic function indicators include left ventricular end-diastolic volume, peak ejection rate, peak filling rate, peak filling time and filling 1/3 of the first 1/3 of the end of diastole.

Diagnosis and diagnosis of hypertrophic cardiomyopathy in children

diagnosis

According to medical history, family history, clinical manifestations and echocardiography, diagnosis can generally be confirmed.

1. Obstructive HCM diagnosis of HCM must first exclude cardiac hypertrophy caused by other causes, such as congenital heart disease, high blood pressure, endocrine and metabolic diseases, etc., if there is chest pain, syncope, palpitations and other symptoms, cardiac examination found early and late precordial murmur The intensity of the murmur changes with the changes of body position, breath holding, fist clenching, etc. When the electrocardiogram shows left ventricular hypertrophy, ST-T changes and abnormal Q waves, the diagnosis of obstructive HCM should be considered. If the following conditions are met: cardiac catheter showed left ventricular outflow tract systolic pressure difference > 2.67 kPa (20 mmHg), or cardiovascular angiography showed left ventricular outflow tract stenosis; echocardiogram showed SAM phenomenon, septal thickness / left ventricular posterior wall The thickness ratio is 1.3 to 1.5, and the obstructive HCM can be diagnosed.

2. Non-obstructive HCM Clinically, although there are symptoms such as palpitations, fatigue, dizziness, etc., but no abnormalities in cardiac examination; echocardiographic indication of ventricular septum and left ventricular posterior wall thickening, no left ventricular enlargement, cardiac output is basically normal, no SAM phenomenon, ECG has ST-T changes and abnormal Q wave, should consider the diagnosis of non-obstructive HCM, if the cardiac catheter test shows no difference in pressure between left ventricular outflow tract and left ventricle, left ventricular angiography shows left ventricular wall thickening However, there is no left ventricular outflow tract stenosis and left ventricular volume increase, no cardiac output decreased, can confirm the diagnosis of non-obstructive HCM.

3. Combined with diastolic dysfunction HCM combined with diastolic dysfunction, children currently have no diagnostic criteria for diastolic dysfunction, but if the following conditions occur, consider the diagnosis of diastolic dysfunction: history of HCM and left ventricular dysfunction, and X-ray examination showed pulmonary congestion and normal or slightly larger heart shadow; echocardiography showed that the left ventricular end-diastolic diameter did not expand, the wall thickness was normal or thickened, and the inner diameter shortening rate was >25%, while rapid filling Ratio of mitral flow velocity to atrial systolic systolic (E/A ratio) 1, diastolic anterior mitral regurgitation (EF slope) decreased; radionuclide examination of abnormal left ventricular diastolic function; cardiac catheter Examination showed that the pulmonary capillary wedge pressure was >2.4 kPa (18 mmHg) without left ventricular end-diastolic volume; the invasive or non-invasive examination of the left ventricular ejection fraction was normal.

Differential diagnosis

Secondary ventricular hypertrophy

(1) Congenital aortic coarctation and secondary ventricular hypertrophy of aortic stenosis: this disease should be differentiated from congenital aortic coarctation and secondary ventricular stenosis of the aortic stenosis, the former upper extremity artery pulsation is strong, The blood pressure is high, and the lower extremity arterial pulsation is weakened or disappeared, and the blood pressure is not detected. The latter has a typical aortic valve area systolic jet murmur and systolic snoring, the second sound of the aortic area is weakened, and the chest X-ray is visible. The aortic segment has stenosis and posterior dilatation. Echocardiographic examination shows a small aortic valve opening, left heart catheterization, and aortic stenosis. There is a significant systolic pressure difference between the left ventricle and the aorta, and HCM systolic pressure. The step difference is seen between the left ventricular outflow tract, and the infant HCM still needs to be differentiated from the following ventricular hypertrophy:

(2) Infants born to a diabetic mother: have ventricular hypertrophy and hypoglycemia, and most of them relieve themselves within a few months after birth.

(3) Pompe disease: ventricular hypertrophy, complicated with heart failure, children with large tongue, low muscle strength, shortened EC interval of the electrocardiogram, QRS wave high voltage, skeletal muscle biopsy can confirm.

(4) Noonan syndrome: congenital pulmonary stenosis with special face and mental retardation.

2. Identification with harmless noise

Asymptomatic people should be differentiated from harmless murmurs.

3. Primary endocardial fibroelastosis

Infants with HCM often have heart failure, which should be distinguished from primary endocardial fibroelastosis. The left ventricle is obviously enlarged, systolic dysfunction, and no ventricular hypertrophy.

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