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Lecture notes, cheat sheets
Hospital therapy. Diseases of the cardiovascular system. Hypertrophic cardiomyopathy (lecture notes)
Directory / Lecture notes, cheat sheets Table of contents (expand) LECTURE № 3. Diseases of the cardiovascular system. Hypertrophic cardiomyopathy Hypertrophic cardiomyopathy (HCM) is a non-coronary disease of the ventricular myocardium (mainly the left), characterized by massive hypertrophy of their walls with protrusion of the interventricular septum (IVS) into the cavity of the right ventricle, which can be significantly thickened, a decrease in the internal volume of the ventricles, normal or increased contractility of the ventricular myocardium and impaired relaxation (diastolic dysfunction). The most common is isolated hypertrophy of the interventricular septum (isolated hypertrophic subaortic stenosis - IHSS) or the apical part of the ventricles. Classification. Classification of HCM by localization of hypertrophy (E. D. Wigle et al., 1985 with additions). I. LV hypertrophy. 1) Asymmetric hypertrophy, in which myocardial hypertrophy of individual walls or segments of the ventricles occurs (including IVS hypertrophy - 90% with or without obstruction of the outflow tract of the left ventricle, midventricular - 1%, apical hypertrophy of the left ventricle - 3%, free wall hypertrophy left ventricle and posterior part of the IVS - 1%). 2) Symmetrical (concentric) hypertrophy of the left ventricle, when myocardial hypertrophy extends to all walls of the ventricles, occurs in 5% of cases. II. Hypertrophy of the pancreas. In the case when myocardial hypertrophy prevents the normal outflow of blood from the ventricles of the heart, they speak of an obstructive form of HCM. In other cases, HCM is non-obstructive. Etiology. The disease can be either congenital or acquired. Congenital HCM is inherited in an autosomal dominant manner. Within the same family, various forms and variants of HCM can be observed. Most often, asymmetric hypertrophy of the interventricular septum is inherited. The acquired form of HCM occurs in elderly patients with a history of arterial hypertension. The prevalence is 0,02-0,05%. The reasons for the development of acquired HCM are not fully understood. According to one of the proposed hypotheses, individuals with acquired HCM in the prenatal period develop a defect in the adrenergic receptors of the heart involved in the regulation of cardiac activity, in particular heart rate. As a result, the sensitivity to norepinephrine and similar hormones, which increase the heart rate, is significantly increased, which affects the development of myocardial hypertrophy in them, and eventually HCM. Pathohistological picture. Disoriented, incorrect, chaotic arrangement of cardiomyocytes and myofibrils in cardiomyocytes, myocardial fibrosis is a violation of the architectonics of the heart muscle. Pathogenesis. Hemodynamic disorders arise due to impaired diastolic function of the heart. During diastole, insufficient blood flows into the ventricles (especially the left) due to their density and rigidity, which leads to a rapid rise in end-diastolic pressure. Both increased myocardial stiffness and increased intraventricular pressure cause less blood to be ejected from the ventricle during systole. For adequate delivery of oxygen to the organs and tissues of the body (with the normal functioning of the cardiovascular system), for the implementation of any load, the release of blood from the heart must increase. Accordingly, in response to the load, the heart rate increases. With the development of HCM, the filling of the heart with blood also suffers at rest, and with an increase in the heart rate during the period of exercise, it is even more negatively affected. As a result of this, there is no adequate increase in the pumping function of the heart during exercise in HCM. Physical activity in HCM affects the increase in intraventricular pressure, which leads to an increase in pressure in the left atrium located above, as well as in the vessels of the small (pulmonary) circulation. Under these conditions, hyperfunction and hypertrophy of the left atrium develop, and later - pulmonary hypertension ("passive"). As a result, shortness of breath occurs, which is proportional to the degree of load. Since during exercise the ejection of blood from the left ventricle does not correspond to the increase in load, the blood flow in the coronary arteries that feed the heart muscle itself begins to suffer. It also plays an important role that in HCM there is a discrepancy between a significant mass of hypertrophied myocardium and the possibility of coronary blood supply, which remains the same as in healthy people. The decrease in blood flow through the coronary arteries leads to the occurrence of angina pectoris in the middle and in the left half of the chest, radiating to the left arm, under the left shoulder blade. Like shortness of breath, angina pectoris is provoked by physical exertion. In some cases of HCM during exercise, the cerebral blood supply also deteriorates, resulting in syncope. It should be noted that to reduce the increase in intraventricular pressure during exercise, there is a compensatory mechanism, the operation of which is based on the fact that the cavity of the left atrium expands, and the thickness of its walls increases. As a result, there is an additional filling of the left ventricle with blood during exercise. However, this is only a temporary compensation due to the fact that the reserve of the left atrium as a "pump" is insignificant, and a significant expansion of the cavity of the left atrium leads to the development of atrial fibrillation. clinical picture. HCM is characterized by an extreme variety of symptoms, which causes misdiagnosis. The presence and timing of complaints in HCM are mainly determined by 2 factors: the form of HCM and the location of the lesion. The most powerful chamber of the heart is the left ventricle, therefore, with hypertrophy of the myocardial walls, complaints may not appear for a long time. Isolated damage to the right ventricle of the heart is extremely rare. In the non-obstructive form of HCM, when nothing interferes with the outflow of blood from the ventricle, the patient may not present any complaints. Sometimes there may be shortness of breath (with significant physical exertion), interruptions in the work of the heart, as well as an irregular heartbeat. In the obstructive form of HCM, the ejection of blood from the heart during exercise is significantly reduced due to the presence of an obstruction to the outflow of blood from the ventricle. In this case, the typical complaints are shortness of breath on exertion, angina pectoris and fainting. The disease is characterized by a slow progression of complaints from the moment of its onset. Due to the similarity of complaints (pain in the region of the heart and behind the sternum) and study data (intense systolic murmur), rheumatic heart disease and coronary heart disease are most often misdiagnosed. The clinical picture of HCM is: 1) signs of ventricular myocardial hypertrophy (mainly left); 2) a sign of insufficient diastolic ventricular function; 3) variable signs of left ventricular outflow tract obstruction. Diagnostics. In the process of diagnostic search, the most significant is the detection of systolic murmur, altered pulse and displaced apical impulse. The auscultatory picture of the heart in patients with obstructive HCM has a number of features: the maximum sound of the systolic murmur (ejection murmur) is determined at the Botkin point and at the apex of the heart, the severity of the murmur is proportional to the degree of obstruction, its intensification occurs when the patient stands up abruptly, as well as during the Valsalva test ; II tone is always preserved; noise is not carried out on the vessels of the neck. The pulse is usually high and fast. This is due to the absence of narrowing in the outflow tracts from the left ventricle at the beginning of systole, but then, with the contraction of powerful muscles, a “functional” narrowing of the outflow tracts appears, as a result of which the pulse wave decreases prematurely. The apex beat in about 1/3 of cases has a "double" character: at first, on palpation, a blow is felt from contraction of the left atrium, then from contraction of the left ventricle. For the convenience of identifying this property of the apex beat, palpation is best done with the patient lying on his left side. For the diagnosis of HCM, echocardiography data are of the greatest importance, allowing to clarify the anatomical features of the disease, the severity of myocardial hypertrophy, obstruction of the outflow tract of the left ventricle. The following signs are revealed: asymmetric hypertrophy of the IVS, more pronounced in the upper third, its hypokinesis; systolic movement of the anterior leaflet of the mitral valve in the anterior direction; contact of the anterior leaflet of the mitral valve with the IVS in diastole. Nonspecific signs are: hypertrophy of the left atrium, hypertrophy of the posterior wall of the left ventricle, a decrease in the average speed of the diastolic cover of the anterior leaflet of the mitral valve. On the ECG, any specific changes are found only with sufficiently developed left ventricular hypertrophy. By recording an ECG for 24 hours (Holter monitoring), existing heart rhythm disturbances are detected. An ECG test with dosed physical activity using a bicycle ergometer or treadmill allows you to assess the severity of the symptoms of the disease, its prognosis and develop appropriate treatment. Isolated hypertrophy of the IVS causes an increase in the amplitude of the Q wave in the left chest leads (V5-6), which complicates the differential diagnosis with focal changes due to myocardial infarction. However, a small width of the Q wave allows excluding a myocardial infarction. In the process of developing hemodynamic overload of the left atrium, the ECG may show signs of left atrial hypertrophy: widening of the P wave for more than 0,10 s, an increase in its amplitude, the appearance of a biphasic P wave in lead V1 with the second phase increased in amplitude and duration. X-ray diagnostics is important only in the advanced stage of the disease, when an increase in the left ventricle and left atrium, an expansion of the descending part of the aorta can be determined. On the phonocardiogram, the amplitudes of I and II tones are preserved, which is a differential sign of HCM from stenosis of the aortic orifice, and systolic murmur of varying severity is also detected. Invasive research methods (probing of the left parts of the heart, contrast angiography) are currently not mandatory, since echocardiography provides quite reliable information for making a diagnosis. However, sometimes these methods are used in controversial cases to clarify the diagnosis or in preparing patients for surgery. Cardiac probing is used under X-ray television control. Technique for performing the method: by puncturing a large artery under local anesthesia with the further introduction of a special catheter into the heart cavity, the pressure gradient (difference) between the left ventricle and the aorta departing from it is measured. Normally, this gradient should not be. However, with HCM, there is a pressure difference between the left ventricle and the aorta from 50 to 150 mm Hg. Art., an increase in end-diastolic pressure in the cavity of the left ventricle up to 18 mm Hg. Art. The pressure gradient decreases after the introduction of β-blockers. Also, during sounding of the heart, a contrast agent is injected into the cavity of the ventricle (ventriculography) to study its anatomical features. In a number of patients (as a rule, these are persons over 40 years old), angiography of the coronary arteries (coronary angiography) is simultaneously used before heart surgery to clarify the etiology of angina pectoris and exclude concomitant coronary artery disease. Treatment. The basis of drug treatment for HCM is drugs that improve blood flow to the ventricles of the heart in diastole. These drugs are a group of β-blockers (anaprilin, atenolol, metoprolol and propranolol, 160-320 mg/day, etc.) and a group of calcium ion antagonists (verapamil, but with caution). Novokinamid and disopyramide also reduce heart rate and have an antiarrhythmic effect. At the very beginning of treatment, small doses of these drugs are used, then the dosage is gradually increased to the maximum tolerated by the patient. β-blockers are used with caution in diabetes mellitus, bronchial asthma and some other diseases. When treating with these drugs, constant monitoring of blood pressure and pulse rate is necessary. Dangerous is a decrease in pressure below 90/60 mm Hg. Art. and heart rate below 55 per minute. If a patient has dangerous rhythm disturbances that cannot be treated with β-blockers or calcium ion antagonists, then other antiarrhythmic drugs are additionally used in the treatment of such patients. The appointment of anticoagulants is recommended for paroxysmal arrhythmias and atrial fibrillation, as well as in the presence of blood clots in the heart chambers (warfarin, etc.). During the period of treatment with these drugs, it is necessary to regularly monitor a number of indicators of the blood coagulation system. With a significant overdose of anticoagulants, external (nasal, uterine, etc.) and internal bleeding (hematomas, etc.) are possible. Surgical treatment is performed in patients with obstructive HCM when medical treatment is not effective or when the gradient between the left ventricle and aorta is more than 30 mm Hg. Art. (the operation of myotomy or myectomy is performed - excision or removal of a part of the hypertrophied myocardium of the left ventricle). Mitral valve replacement and non-surgical IVS ablation are also performed. Prevention. All patients with HCM, especially those with an obstructive form, are contraindicated in sports that can significantly increase physical activity over a short period of time (athletics, football, hockey). Prevention of the disease lies in early diagnosis, which makes it possible to begin early treatment of the disease and prevent the development of severe myocardial hypertrophy. It is mandatory to perform echocardiography in genetic relatives of the patient. Screening ECG and EchoCG, which are carried out during an annual medical examination, are also important for diagnosis. In patients with obstructive HCM, it is necessary to prevent infective endocarditis (antibiotic prophylaxis, etc.), since the presence of obstruction creates conditions for the development of this life-threatening condition. Author: Mostovaya O.S. << Back: Diseases of the cardiovascular system. Cardiomyopathy. Dilated cardiomyopathy >> Forward: Diseases of the cardiovascular system. Restrictive cardiomyopathy
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