Hyperthyroid cardiomyopathy

Introduction to hyperthyroidism The thyroid hormone secreted by the thyroid gland has different degrees of influence on the metabolism and physiological activities of many organs of the body, and the influence on the cardiovascular system is very prominent. In hyperthyroidism, the effects of elevated T3 and/or T4 in the heart on cardiac conduction and cardiomyocytes can lead to a series of complications leading to hyperthyroidism. basic knowledge The proportion of illness: the incidence rate is about 0.004%-0.005% Susceptible people: no special people Mode of infection: non-infectious Complications: arrhythmia heart failure

Causes of hyperthyroidism cardiomyopathy

(1) Causes of the disease

The etiology of this disease has not yet been fully defined, and factors such as autoimmune damage, genetic susceptibility and mental stimulation can induce or cause the disease.

(two) pathogenesis

The pathogenesis of hyperthyroid cardiomyopathy may be related to the following factors:

Pathogenesis

(1) thyroid hormone excitatory adenylate cyclase: thyroid hormone has the same effect as catecholamine, can excite adenylate cyclase, so that myocardial contractility is enhanced, thyroid hormone can directly act on the myocardium, T3 can increase myocardial cell membrane The number of beta receptors promotes adrenaline-induced cAMP production in cardiomyocytes. Thyroid hormone promotes the release of Ca2 from the sarcoplasmic reticulum of cardiomyocytes, thereby activating proteins involved in myocardial contraction and enhancing contractility.

(2) thyroid hormone acts directly on the myocardium: this can shorten the action potential of the sinus node; the excitability of the atrial muscle increases, and the refractory period shortens and causes atrial fibrillation. In experimental animals, thyroxine can increase the atrial rate, and diastolic period Extremely short, thyroid hormone toxicity and sympathetic nerve excitability combined to cause sinus tachycardia, while long-term atrial fibrillation and tachycardia can cause cardiomyopathy.

(3) thyroid hormone strengthens glycogen decomposition: thyroid hormone strengthens myocardial glycogen catabolism, frustrates the glycolysis process of cardiomyocytes, and suppresses oxidative phosphorylation, resulting in decreased left ventricular function.

(4) When thyroid hormone has positive change to the heart, variable force and shifting effect: in the early stage, the heart rate can be accelerated, the myocardial contractility is strengthened, the cardiac output is increased, the myoglobin synthesis is increased, and the myocardial cell hypertrophy is changed. Long-term action of thyroid hormone on the myocardium will lead to increased energy consumption of the heart, and the myocardial contractility will gradually weaken, eventually causing heart failure. When heart failure occurs in patients with hyperthyroidism, the cardiac output is decreased, but the absolute value is still higher than normal. It is a high-flowing heart failure. When the condition is further aggravated, the cardiac output can be reduced to normal or below normal.

2. Pathology

Hyperthyroidism can lead to enlarged heart, hypertrophy of the heart, microscopic myocardial interstitial edema, interstitial fibrosis, small focal myocardial degeneration and necrosis, with alternative fibrous granulation tissue, no or only a small amount of inflammatory cell infiltration The above pathological changes are lighter. Animal experiments have shown that after administration of a large amount of thyroid hormone, it can cause hypertrophy, degeneration, interstitial fibrosis, a small amount of lymphocyte infiltration, mitochondrial changes under electron microscope, and sarcoplasmic reticulum expansion.

Hyperthyroidism prevention of cardiomyopathy

1, arrhythmia is often seen when hyperthyroidism, the most common is atrial fibrillation, it is reported that 10% to 22% of patients with hyperthyroidism complicated with atrial fibrillation, the pathophysiological basis of hyperthyroidism atrial fibrillation is not fully understood, atrial fibrillation Maintenance requires the formation of multiple reentry loops. Currently, only Na-K-ATPase activity of cardiomyocytes is enhanced during hyperthyroidism, which promotes sodium efflux, potassium influx, affects myocardial cell electrophysiology, clinically some patients, and serum promotion. Thyroid hormone (TSH) is less than 0.1mU / L, T3, T4 concentration is in the normal range, there is no clinical manifestation of hyperthyroidism, called subclinical hyperthyroidism, the elderly with low serum TSH should be observed and may develop into clinical Dominant hyperthyroidism and atrial fibrillation, whether antithyroid drugs can prevent its occurrence is not known, but patients receiving thyroid hormone therapy or low serum TSH should avoid excessive doses of thyroid hormone to inhibit TSH to reduce atrial fibrillation The danger.

2. For elderly people over 60 years old, low serum TSH is a risk factor for atrial fibrillation. Because myocardial lesions of hyperthyroidism are reversible, the underlying prevention and treatment measures are still to restore normal thyroid function, beta blockade. Drugs or angiotensin-converting enzyme inhibitors (ACEI) help to improve certain cardiovascular symptoms. Hyperthyroidism can aggravate or worsen heart disease and lead to heart failure, causing ventricular enlargement, heart failure and even sudden death. According to reports, the incidence of congestive heart failure in patients with hyperthyroidism is about 6%, older than 60 years old, older patients are more likely to occur, general clinical symptoms of hyperthyroidism and hyperthyroidism, elevated levels of thyroid hormone It has nothing to do with enzymatic changes, but is related to age and hyperthyroidism. Therefore, prevention and treatment of hyperthyroidism must be an early treatment for hyperthyroidism, especially for the elderly over 60 years old.

Hyperthyroidism cardiomyopathy Complications arrhythmia heart failure

Patients with hyperthyroidism are prone to arrhythmias (the most common atrial fibrillation 10% to 22%), coronary circulatory insufficiency, heart failure and other complications.

Symptoms of hyperthyroidism cardiomyopathy Common symptoms Goiter, dyspnea, weakness, arrhythmia, angina, liver enlargement, tachycardia, diarrhea, heart failure, fatigue

Symptom

(1) General symptoms: patients with hyperthyroidism often have heat, sweating, finger shaking, emotional irritability, excessive appetite, polyphagia, weight loss, muscle weakness, fatigue and hyperactivity of the intestines (occasionally diarrhea).

(2) palpitations: sinus tachycardia often occurs, which is proportional to the increase of metabolic rate. The heart rate is still increased at rest. This disease is prone to a variety of tachyarrhythmia, with atrial, ventricular or atrioventricular node. Premature beats are most common, and paroxysmal or persistent atrial fibrillation or flutter often occurs.

(3) Difficulty breathing: the occurrence of dyspnea is related to the large oxygen consumption and less lung capacity. This is different from the dyspnea due to heart failure. In severe cases, symptoms of congestive heart failure such as labor and nighttime paroxysmalness may occur. Difficulty breathing.

(4) Pain in the precordial area: the pain in the precordial area is mild, generally a heavy pain, sometimes showing typical angina pectoris, often caused by atrial arrhythmia, or hyperthyroidism can increase coronary atherosclerosis Caused by a hardened heart load (very few patients with hyperthyroidism combined with hyperlipidemia), precordial pain can disappear after the treatment of hyperthyroidism.

2. Physical examination

(1) Goiter: The thyroid gland is diffusely enlarged.

(2) Exophthalmia: Eye signs of hyperthyroidism include gaze, enlarged ocular fissure, prominent eyeball, rapid ocular lag, upper eyelid retraction, mild scleral congestion, and invasive exophthalmology. Eyelid pain, tearing, foreign body sensation, fear of light, tissue hyperplasia after sacral, infiltration of exophthalmos and extraocular muscle lymphocytes, resulting in eye muscle weakness resulting in diplopia.

(3) changes in blood pressure: systolic blood pressure increased, diastolic blood pressure decreased slightly, pulse pressure difference increased, a small number of patients with large pulse pressure difference, it can be seen obvious peripheral vascular signs.

(4) Heart rate changes: heart rate is usually 100 to 120 times / min, patients with hyperthyroidism crisis can often be as fast as 180 to 200 times / min.

(5) Heart changes: When hyperthyroidism causes hyperthyroidism, due to the strengthening of myocardial contractility, a strong pulsating apex can be seen during physical examination, and the severe heart can spread to the chest wall, and the first heart sound can be heard in the apical region. The heart enlarges, mainly the left ventricle enlarges, and there are two to three levels of murmur in the apical region. When the heart is insufficiency, the lung bottom blisters can appear. When the right heart is incomplete, the jugular vein appears. Angry, swollen liver and lower extremity edema.

(6) Others: Damp heat, muscle tremors, etc. are very important for diagnosis, but in some hyperthyroid cardiomyopathy, the symptoms of hyperthyroidism may not be obvious, and there are no signs such as goiter and exophthalmos.

The current diagnostic criteria are not yet uniform.

Examination of hyperthyroidism

First, laboratory inspection

Thyroid function test

The most specific method for diagnosing hyperthyroidism is to check thyroid function. However, in the experimental examination of hyperthyroidism, it is found that the older the T3, the lower the T4 value is, or even normal, but the FT3 and FT4 are both. Increased, so in this case, should pay attention to check FT3 and FT4, if necessary, do hypersensitivity TSH check to exclude subclinical hyperthyroidism.

2. Serum troponin T detection

Troponin T (TnT) is a sensitive and specific serum marker that has been developed in recent years to reflect myocardial damage. TnT is mainly a structural protein of cardiomyocytes, only 5% is present in the cytoplasm in free form, and myocardial cells are damaged. The structural protein breaks down and the free form of TnT is quickly released into the blood. Therefore, it is an ideal indicator for early diagnosis of myocardial injury. The TnT content in normal human blood is extremely low, indicating that TnT is released into the bloodstream only after myocardial injury. In short, it takes a certain process to develop from hyperthyroidism to hyperthyroidism. It is still difficult to determine when myocardial injury occurs in patients with hyperthyroidism, but blood TnT can be elevated in early myocardial damage. TnT is one of the effective methods for early detection of thyroid hyperthyroidism in the elderly. However, if the onset time is long, the diagnosis cannot be ruled out even if TnT is normal. It should be confirmed in combination with other clinical symptoms and signs.

3. Neuropeptide Y detection

In recent years, neuropeptide Y (NTY) has become more and more widely used in cardiovascular and hypertension diseases. The dynamic changes of NTY in hyperthyroidism have only been reported in foreign countries. The increase in NTY during hyperthyroidism is due to the heart. Coronary artery contraction, causing myocardial ischemia, causing negative cardiac muscle function, causing a decrease in left ventricular ejection fraction, and some patients have cardiac dysfunction. In addition, because NTY and NTY nerve fibers are not only in sinus node and house There is a presence around the ventricle, and it is also found in the atrioventricular bundle, the left and right bundle branches, and the branch of the Pu's fiber. NTY acts as a regulatory factor to regulate other media and exerts interference with the cardiac conduction system, participating in the mechanism of arrhythmia, and the NTY is If hyperthyroidism is elevated and accompanied by clinical symptoms, electrocardiogram, cardiac function changes, support the diagnosis of hyperthyroidism cardiomyopathy, if the TnT is also elevated, it supports the diagnosis.

Second, imaging examination

Electrocardiogram

Electrocardiogram reflects abnormal cardiac conduction, the most common are sinus tachycardia, atrial fibrillation, premature contraction, atrioventricular block and non-specific ST-T changes. Electrocardiogram is simple, convenient, and non-invasive. However, because there are too many factors affecting the electrocardiogram, it is easy to miss the diagnosis of heart disease with electrocardiogram alone. If combined with other tests, it is helpful for early diagnosis.

2. Chest X-ray film

X-ray films mainly showed pulmonary congestion, pulmonary artery segmentation and obvious bulging. The heart shape was mostly mitral valve heart, the heart was mainly right ventricular enlargement, followed by left and right ventricle enlargement and left ventricular enlargement. Left atrial enlargement also occurs in the case of power failure (Fig. 1), but there are also reports in the literature that the heart of hyperthyroidism has no obvious enlargement or slight increase, and only the pulmonary artery segment is prominent.

3. Echocardiography

Hyperthyroidism patients with increased total blood volume, myocardial contractility increased with a high dynamic state, such as changes in cardiac structure and function, may be hyperthyroidism, hyperthyroidism, heart disease, ultrasound manifestations are:

(1) ventricular septum and left ventricular free wall thickening: ventricular septum and left ventricular posterior wall movement increased, which is due to the direct effect of thyroid hormone on the heart, resulting in increased myocardial protein synthesis, myocardial cell growth accelerated, cardiac hypertrophy.

(2) Cardiac cavity enlargement: In the high dynamic state, the blood flow of the aortic valve mouth is increased through the mitral valve, the long-term capacity overload is excessive, and the diastolic pressure is increased, which can enlarge the heart chamber.

(3) Heart function reduction: chronic severe cases, high-dynamic state to low-power state, ultrasound findings similar to dilated cardiomyopathy, congestive heart failure, simple hyperthyroidism after heart disease, heart disease signs can disappear .

(4) Valve function: hyperthyroidism combined with high incidence of mitral regurgitation, may be due to hyperthyroidism and mitral regurgitation are both related to genetic factors or autoimmune diseases, a large number of thyroid hormones It can affect the function of the mitral valve and cause prolapse. The incidence of hyperthyroidism combined with mitral regurgitation is related to the time of treatment.

(5) Color Doppler flow imaging: high cardiac output is a common result of increased heart rate and increased contractility, and increased stroke output. Although hyperthyroidism has diastolic dysfunction, the maximum flow rate increases. There is a significant difference compared with coronary heart disease.

4. Nuclide check

Normal human myocardial tomographic images suggest uniform radioactivity distribution, no sparse area and variegated changes. When hyperthyroidism develops heart disease, 99Tc perfusion of imaging agent appears as a sparse area of myocardial radioactivity distribution, diffuse unevenness or The variegated changes reflect the myocardial ischemia, site and extent of damage to the thyroid function.

Diagnosis and differentiation of hyperthyroidism

Diagnostic criteria

1. The New York Heart Association of the United States has proposed a diagnostic standard for hyperthyroidism.

(1) Hyperthyroidism that has been diagnosed.

(2) The patient has one or more of the following symptoms:

1 heart enlarges.

2 arrhythmia, such as atrial fibrillation, atrioventricular block, etc., but only sinus tachycardia or pre-contraction is not included.

3 heart failure.

(3) Heart disease other than other causes.

(4) After the treatment of hyperthyroidism, the heart disease becomes basically cured.

2. The diagnostic criteria for hyperthyroidism cardiomyopathy proposed by Chen Yuzhu in China are as follows:

(1) Hyperthyroidism with atrial fibrillation, premature contraction or enlarged heart.

(2) High output refractory heart failure without other causes.

(3) The above situation improved or significantly improved after hyperthyroidism control.

3. There should be a high degree of suspicion about the following.

(1) Unexplained atrial fibrillation or atrial flutter, and the ventricular rate is not easy to control.

(2) The main heart failure or the first heart failure, but no valvular heart disease, pulmonary heart disease or congenital heart disease history, no signs and cardiac ultrasound, and the effect of diuretics is not good.

(3) sinus tachycardia, heart enlargement or abnormal electrocardiogram, which can be explained without reason, etc., the above situation must be combined with various detection methods for identification.

Differential diagnosis

The disease should be differentiated from congenital heart disease, pulmonary heart disease, rheumatic heart disease.

Congenital heart disease

Both of them had pulmonary congestion and the heart was mitral, but the disease had heart murmurs after birth, and the right ventricle and right atrium increased.

2. Pulmonary heart disease

There are many chronic respiratory diseases, symptoms and signs of emphysema and obstructive pulmonary hypertension. The heart is slightly enlarged with mitral valve type, right ventricle, pulmonary artery spurs; chest X-ray shows lung texture disorder , pulmonary interstitial fibrosis and emphysema manifestations.

3. Rheumatic heart disease mitral valve disease

There may be a history of rheumatic fever; the heart is enlarged with the left atrium, the apex can be heard and the diastolic murmur, the chest X-ray shows: the lung congestion changes, the mitral valve heart.

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