Hypothyroid cardiomyopathy

Introduction to hypothyroid cardiomyopathy Hypothyroidism (hypothyroidism) is a clinical syndrome caused by insufficient thyroid hormone secretion and low body metabolism. Hypothyroidism can occur in the fetus, neonatal period (small ailments), children, adolescents (young-type hypothyroidism) and adults (adult-type hypothyroidism), different onset age, clinical manifestations vary widely, but can be different Degree to the cardiovascular system, causing hypothyroid heart disease. basic knowledge The proportion of illness: 0.02% - 0.07% Susceptible people: no specific population Mode of infection: non-infectious Complications: ischemic cardiomyopathy, angina pectoris, arrhythmia

Causes of hypothyroid cardiomyopathy

(1) Causes of the disease

According to the cause of hypothyroidism can be divided into:

1. Primary hypothyroidism is a hypothyroidism caused by thyroid disease.

2. Secondary hypothyroidism, including pituitary lesions caused by hypothyroidism (TSH) insufficient hypothyroidism and hypothalamic thyroid stimulating hormone releasing hormone (TRH) secretion reduced pituitary TSH reduction caused by hypothyroidism,

3. Peripheral hypothyroidism (thyroid hormone resistance syndrome) is a hypothyroidism caused by no reaction of thyroid hormones around the tissue.

(two) pathogenesis

Pathogenesis

Hypothyroidism, insufficient secretion of thyroid hormone or surrounding tissue is not sensitive to thyroid hormone, the body's basal metabolic rate is low, the metabolic needs of tissues and organs and blood supply are reduced, and the energy supply and oxygen consumption of the heart are reduced. Therefore, the stroke volume is reduced. , heart rate slows down, cardiac output is reduced, due to reduced heat production, in order to maintain constant body temperature, skin vasoconstriction, skin and appendage dystrophies, increased capillary permeability and water-soluble mucopolysaccharide and mucin accumulation in tissues , causing serous effusion, such as pleural effusion, ascites, pericardial effusion and systemic mucinous edema, due to mucinous edema of the myocardium and its interstitial, many enzyme activities of the myocardium are inhibited, myocardial sensitivity to catecholamines is reduced, Reduced catecholamine receptors in the myocardium, weakened myocardial contractility, myocardial pseudohypertrophy, enlarged heart, slowed down of blood cholesterol catabolism during hypothyroidism, increased cholesterol, triacylglycerol and low-density lipoprotein, long-term hyperlipidemia Promoting atherosclerosis, especially coronary arteries, has a pathological basis for angina.

2. Pathology

The pathological changes of the heart are non-specific. The naked eye sees a spherical enlargement of the heart. The surface of the heart is pale and soft. The myofibrils are swollen under the light microscope, the streaks disappear and the interstitial fibrosis, the size of the myocardial cells varies, and the deformation and vacuolization Denaturation, mucin and mucopolysaccharide deposition between cardiomyocytes, sarcolemma visible under electron microscope, serrated nucleus membrane, mitochondrial swelling, mitochondrial sputum reduction, sarcoplasmic reticulum and transverse tube expansion.

Hypothyroidism prevention of cardiomyopathy

1. Correction of iodine deficiency Because the basic cause of endemic cretinism is iodine deficiency, correcting iodine deficiency can prevent this disease. In areas where endemic cretinism is prevalent, iodine can be added during pregnancy and eat more iodine-containing food. And add iodized oil as appropriate. After the baby is born, iodized salt, lipiodol and other iodine agents can be used for comprehensive prevention.

2. Hypothyroidism is the main complication of 131I treatment and thyroid surgery. The incidence of hypothyroidism in the early 1 year after treatment is 5% to 10%, and the cumulative incidence is 2.8% to 5.0% every year. Therefore, it has been done. Patients with 131I and thyroid surgery should frequently monitor thyroid function, early detection of hypothyroidism, and early treatment.

Hypothyroidism cardiomyopathy complications Complications ischemic cardiomyopathy angina pectoris arrhythmia

The disease is prone to ischemic cardiomyopathy, angina pectoris, arrhythmia and other complications.

Symptoms of hypothyroidism Cardiomyopathy Common symptoms Bradycardia palpitations Heart sounds low blunt cardiac output reduction

Hypothyroidism

Hypothyroidism, serum T4 deficiency, myocardial interstitial mucin deposition and myocardial cyclase reduction, myocardial cell mucinous edema, myofibril degeneration and necrosis leading to decreased myocardial metabolism, decreased cardiac contractility and decreased cardiac output, and Can cause heart enlargement and myocardial pseudohypertrophy, heart enlargement is obvious in the left ventricle, right ventricular enlargement or double ventricular enlargement, easy to be confused with other cardiomyopathy, clinical manifestations are mostly palpitations, shortness of breath, increased after exertion, low blood pressure , bradycardia, low heart bluntness and low cardiac output, angina pectoris, heart failure and pulmonary edema rarely occur. Once heart failure occurs, due to prolongation of myocardial and myocardial fibers, digitalis is not effective and is prone to poisoning. This can be distinguished from heart enlargement caused by other diseases.

2. hypothyroidism arrhythmia

Due to the long-term severe lack of T4 in the body during hypothyroidism, the activity of Na-K-ATPase and scavenging mucopolysaccharidase in the heart cells of the heart is impaired, resulting in deposition of myocardial interstitial mucin polysaccharides, swelling and ischemia of myocytes, degeneration and necrosis. The sarcolemma fibers are broken, and there are vacuoles and progressive interstitial edema, cell edema, and thickening of the capillary wall in the myocardium. Coulombe et al observed a significant increase in plasma NE concentration and secretion during hypothyroidism, which increased myocardial ischemic injury. And can reduce the electrical stability of the myocardium, causing the autonomic increase of multiple ectopic pacemakers in the atrium, ring reentry in the conduction process in the room, the formation of atrial fibrillation, hypothyroidism caused by the QT interval is more common, but leads to The torsades of ventricular tachycardia are rare. In China, only one case reported by Qin Fuji and others, Liu Yuying et al reported that patients with atrioventricular block may have hypothyroidism, interstitial edema around the conduction system or due to atrioventricular node and conduction system. Due to insufficient blood supply, treatment with thyroid tablets can be reversed and disappeared.

3. hypothyroidism pericardial effusion

Hypothyroidized pericardial effusion is caused by systemic water, sodium retention, pericardial capillary mucopolysaccharide deposition, resulting in increased permeability, leakage of plasma proteins into the lacunar and poor lymphatic drainage. The clinical features are:

1 middle-aged women are more common,

2 heart rate is slow, generally no odd pulse (pulse is weak when inhaling, strong when exhaling), even if there is a large amount of fluid (usually 300 ~ 600ml), the heart rate is still slow or not fast, which is lack of T4, sinus The release of atrial impulses is slowed down, and the heart's sensitivity to catecholamines is reduced and the Ca2-ATPase of myocardium is decreased, resulting in decreased myocardial contractility.

3 venous pressure is not high, only in a large number of pericardial effusion, there is an increase in venous pressure, the degree is asymmetrical compared with pericardial effusion, because the effusion growth rate is slow, the course of disease is long, the pericardium has sufficient extension, the cardiac tampon is also rare,

4 effusion is protein, cell separation phenomenon, the protein in the effusion can reach 60 ~ 80g / L, the number of cells is small, generally within 100 × 109 / L, the former is related to increased capillary permeability, the latter is non-inflammation The cause of the lesion,

5 rarely occur in pericardial friction sounds,

6 blood cholesterol is elevated, although the amount of cholesterol synthesis is decreased in the absence of T4, but its degradation and excretion are blocked more obviously, so cholesterol is elevated,

7 heart enlargement with anemia and chills, dry skin and other hypothyroidism, good response to T4 treatment. In the diagnosis of hypothyroid cardiomyopathy, in addition to the evidence of hypothyroidism, the following conditions are required:

Examination of hypothyroid cardiomyopathy

Serum T3, T4 decreased, TSH increased, caused by thyroid disease itself, if TSH decreased or normal, further use thyroid stimulating hormone releasing hormone stimulation test, if TSH increased, hypothalamic hypothyroidism; if TSH did not respond, then For pituitary hypothyroidism, cardiac function tests showed arm to lung, arm to tongue circulation time prolonged, pre-ejection period (PEP) prolonged, and the ratio of pre-ejection to left ventricular ejection time (PEP/LVET) increased.

Electrocardiogram

The electrocardiogram shows that the heart rate is slow, the QRS complex is low voltage, the T wave is low or inverted, and the amplitude of the P wave is reduced. Occasionally, the PR interval and the QRS interval are prolonged. This change often indicates the infiltration of the cardiac conduction system by mucinous edema. It can disappear after treatment with thyroid hormone preparations. If it persists, it means that there are old myocardial lesions. ST-segment ischemic changes can also be caused by coronary atherosclerosis complicated by this disease.

2. Chest X-ray film

The plain film shows that the heart shadow is universally enlarged, and the heart beats slowly and has a small amplitude (Fig. 1).

3. Echocardiography

In addition to the detection of pericardial effusion, there are signs of cardiac hypertrophy (caused by myocardial pseudohypertrophy), and some cases even show asymmetrical ventricular septal hypertrophy and misdiagnosed as primary hypertrophic cardiomyopathy.

Diagnosis and diagnosis of hypothyroidism

Diagnostic criteria

1. Have a clear manifestation of heart disease, such as slow heart rate or weak heart sounds.

2. Imaging examination showed an enlarged heart.

3. There is an abnormal ECG.

4. Except for other causes of heart disease.

5. The above changes are improved after thyroid hormone therapy. If there is no cause of heart enlargement or pericardial effusion, with heart rate slowing, especially in women, the possibility of hypothyroidism should be considered, basal metabolism. The decrease in the rate, the increase in serum cholesterol levels, the decrease in plasma protein-bound iodine and the decrease in the thyroid 131I uptake rate are all specific indicators.

Differential diagnosis

1. Identification of coronary heart disease with hypothyroidism often with abnormal cardiovascular system, non-specialist often misdiagnosed as coronary heart disease. The following points help to identify:

(1) Hypothyroidism is more common in women: coronary heart disease is common in men.

(2) Heart rate is generally slower in hypothyroidism: in coronary heart disease, the heart rate is relatively fast, especially when the condition worsens.

(3) simple hypothyroidism myocardial angina is less common: due to tissue oxygen consumption and cardiac output parallel, so myocardial oxygen consumption decreased, but angina rarely occurs.

(4) T4 instead of angina disappeared, arrhythmia or ventricular enlargement can be reversed.

(5) Systemic manifestations of hypothyroidism.

(6) Blood T3, T4 decreased when hypothyroidism: TSH increased. Hypothyroidism Arrhythmia is easily misdiagnosed as coronary heart disease. In addition to the above 6 points, the following points are also included:

1 A reduction with coronary heart disease is more typical of angina pectoris: ECG has ST segment depression, more common in men, ineffective after treatment with thyroid tablets or increase angina pectoris.

2 caused by atrioventricular block is often reversible: hypothyroidism angina and myocardial infarction are rare, but if the cardiac output is reduced more than the blood supply required by the heart muscle, angina will also occur.

2. Identification of hypothyroidism with tuberculous pericarditis is easily misdiagnosed as tuberculous pericarditis.

(1) Lack of understanding: The diagnosis is too narrow, and the signs and symptoms of hypothyroidism are misdiagnosed as chronic nephritis, idiopathic edema and other common diseases. The treatment is effective and the attending doctor is satisfied with the original diagnosis, and no longer traces the source.

(2) The medical history is unknown, and the examination is not detailed: the medical history and physical signs of the diagnosis of hypothyroidism are missed. Therefore, hypothyroidism should be considered in the pericardial effusion with the following manifestations:

1 cardiac tamponade symptoms, lack of physical signs or slight;

2 heart rate is slow or unpleasant;

3 pericardial effusion protein is high and the number of cells;

4 edema is significant and the indentation is not obvious (related to the accumulation of hydrophilic mucopolysaccharide in the subcutaneous tissue), urine protein is slight or not;

5 afraid of cold, fatigue, eating less and gaining weight, constipation, dull;

6 multiple serous effusions, all suspected T3, T4 and 131I uptake rate can be diagnosed early, and T4 can achieve satisfactory results in alternative treatment, but should emphasize that the amount of thyroid hormone tablets should be small (10 ~ 20mg / d) Then gradually increase, so as not to suddenly increase the burden of the heart, discomfort, and even induce angina pectoris, myocardial infarction or heart failure risk, the elderly with significant arteriosclerosis or angina, especially should be vigilant.

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