Hypertrophic cardiomyopathy: causes, symptoms, diagnosis, treatment

Hypertrophic cardiomyopathy is a congenital or acquired disease characterized by severe ventricular hypertrophy with diastolic dysfunction, but without increased afterload (unlike, for example, valvular aortic stenosis, coarctation of the aorta, systemic arterial hypertension). Symptoms include chest pain, shortness of breath, fainting and sudden death. Systolic murmur, which increases with a Valsalva test, is usually heard in an obstructive hypertrophic type. Diagnosis is established by echocardiography. Treatment is carried out by b-adrenoblockers, verapamil, disopyramide and sometimes chemical reduction or surgical removal of the obstruction of the outflow pathway.

Hypertrophic cardiomyopathy (HCMC) is a common cause of sudden death in young athletes. It can lead to unexplained syncope and can only be diagnosed when autopsy occurs.

[1], [2], [3], [4], [5]

Causes of hypertrophic cardiomyopathy

Most cases of hypertrophic cardiomyopathy are hereditary. At least 50 different mutations are known to be transmitted by autosomal dominant type of inheritance; Spontaneous mutations occur frequently. Probably a lesion of 1 in 500 people, stenotypic expression is highly variable.

The pathology of the myocardium manifests itself in the disorientation of cells and myofibrils, although these manifestations are not specific for hypertrophic cardiomyopathy. In the most common variants, the upper part of the interventricular septum below the aortic valve is markedly hypertrophied and thickened, with the hypertrophy of the posterior wall of the left ventricle (LV) minimal or absent altogether; this variant is called asymmetric septal hypertrophy. During the systole, the septum thickens, and sometimes the front flap of the mitral valve, already incorrectly oriented due to an irregular ventricular shape, is sucked into the septum due to high-velocity blood flow (Venturi effect), further reducing the outflow tract and reducing cardiac output. The resulting disorder can be called hypertrophic obstructive cardiomyopathy. Less often, the hypertrophy of the middle part of the septum leads to an intracavitary gradient at the level of papillary muscles. In both forms, the distal left ventricle can eventually thin out and expand. Apical hypertrophy also occurs, but it does not complicate outflow, although this variant can lead to obliteration of the apical part of the left ventricle during systole.

The contractility is absolutely normal, as a result of this, the ejection fraction (EF) is normal. Later PV increases because the ventricle has a small volume and is emptied almost completely to maintain cardiac output.

Hypertrophy leads to the formation of a rigid, unyielding chamber (usually LV), which prevents diastolic filling, increases the end diastolic pressure and thus increases pulmonary venous pressure. As the filling resistance increases, the cardiac output decreases, this effect is enhanced by any gradient in the outflow tract. Since tachycardia leads to a decrease in filling time, the symptoms tend to appear mainly during exercise or with tachyarrhythmias.

Coronary blood flow can be worsened, which causes angina pectoris, syncope or arrhythmia in the absence of coronary artery disease. The blood flow may worsen because the ratio of the density of the capillaries to the number of cardiomyocytes is disturbed (unbalance at the capillary / myocyte level) or the diameter of the lumen of the intramural coronary arteries is narrowed due to hyperplasia and hypertrophy of the intima and the middle shell. In addition, with physical exertion, peripheral vascular resistance and diastolic pressure in the root of the aorta decrease, which leads to a decrease in perfusion pressure in the coronary arteries.

In some cases, myocytes gradually die, probably because an imbalance at the capillary / myocyte level causes chronic widespread ischemia. As the myocytes die, they are replaced by common fibrosis. In this case, the hypertrophied ventricle with diastolic dysfunction gradually expands, and systolic dysfunction also develops.

Infective endocarditis can complicate hypertrophic cardiomyopathy due to an abnormality of the mitral valve and rapid blood flow through the outflow tract during an early systole. A late complication is sometimes an atrioventricular block.

[6], [7], [8], [9], [10], [11], [12]

Symptoms of hypertrophic cardiomyopathy

As a rule, the symptoms appear at the age of 20-40 years and are associated with physical activity. These include chest pain (usually resembling typical angina), shortness of breath, palpitations and fainting. Patients may have one or more symptoms. Fainting usually occurs without previous signs during a physical load due to undiagnosed ventricular or atrial arrhythmias and is a marker of high risk of sudden death. It is believed that with hypertrophic cardiomyopathy sudden death occurs due to ventricular tachycardia or fibrillation. Since the systolic function is preserved, patients rarely complain of rapid fatigue.

AD and heart rate are usually normal, symptoms of increased venous pressure are rare. With obstruction of the outgoing tract, the pulse on the carotid arteries has a sharp rise, a split peak and a rapid decrease. The apical impulse can be expressed due to hypertrophy of the left ventricle. Often there is IV heart tone (S ₄ ), associated with a powerful atrial contraction in the background of a weakly compliant left ventricle in late diastole.

Hypertrophy of the septum leads to the appearance of systolic ejection noise, which is not carried around the neck and can be listened to the left side of the sternum in the third or fourth intercostal space. The noise of mitral regurgitation due to a change in the configuration of the mitral valve can be heard on the apex of the heart. When the extracorporeal tract is narrowed, the systolic ejection noise is sometimes heard in the second intercostal space near the left edge of the sternum. The noise of expulsion of the outflow tract of the left ventricle with hypertrophic cardiomyopathy may be enhanced with a Valsalva test (which reduces venous return and diastolic volume of the left ventricle), aortic pressure decrease (for example, nitroglycerin) or during contraction after extrasystoles (which increases the gradient of the vesting tract pressure). Compression of the hands increases aortic pressure, thus reducing the intensity of the noise.

Diagnosis of hypertrophic cardiomyopathy

Presumptive diagnosis is based on the typical noise and symptoms. An unconscious fainting in young athletes should always lead to a survey to exclude HCM. This pathology must be distinguished from aortic stenosis and coronary artery disease, which may be accompanied by similar symptoms.

Perform an ECG and two-dimensional echocardiography (the best noninvasive study that confirms the diagnosis). Chest X-rays are often performed, but usually it does not show pathological changes, since there is no expansion of the ventricles (although the left atrium may be enlarged). Patients with syncope or persistent arrhythmias should be examined in a hospital setting. The exercise test and Holter monitoring are often informative in patients assigned to a high-risk group, although diagnosis in such patients is difficult.

In ECG, usually signs of left ventricular hypertrophy (for example, tooth S in lead V plus R tooth in lead V or V> 35 mm) are usually found . Very deep teeth O from the septum in the leads I, aVL, V and V are often detected with asymmetric septal hypertrophy. When HCMC is sometimes found complex QRS in leads V3 and V4, simulating the previously transferred MI. Teeth usually pathological, most often there are deep symmetrical inverted teeth in leads I, aVL, V5 and V6. Depression of the ST segment in the same leads is also frequent. P wave P in most cases wide, split in leads II, III and aVF, and in leads V and V two-phase, which indicates hypertrophy of the left atrium. The risk of developing the phenomenon of pre-excitation in the Wolff-Parkinson-White syndrome, which leads to arrhythmia, is increased.

Two-dimensional Doppler echocardiography helps differentiate the forms of cardiomyopathy and determine the degree of obstruction of the outflow tract of the left ventricle, including the pressure gradient and the localization of the stenotic segment. This study is particularly significant for monitoring the effectiveness of medical or surgical treatment. With severe obstruction of the vestibular tract, sometimes aortic valve closure is noted in the middle of the systole.

Cardiac catheterization is usually performed only with the planned invasive treatment. Usually, there is no significant stenosis in the coronary arteries, but in the study of metabolism, it is possible to detect myocardial ischemia due to an intramural decrease in the artery lumen, imbalance at the capillary / myocyte level, or abnormal ventricular wall tension. Older patients may also suffer from ischemic heart disease.

[13], [14]

Prognosis and treatment of hypertrophic cardiomyopathy

In general, the annual mortality rate is 1-3% in adults and higher in children. Mortality is inversely proportional to the age at which symptoms occur, and is highest in patients who have frequent sustained ventricular tachycardia or fainting, as well as those who have been resuscitated after sudden cardiac arrest. The prognosis is worse in young patients with a family history of sudden death and in patients older than 45 years with angina or shortness of breath during physical exertion. Death is usually sudden, and sudden death is the most frequent complication. Chronic heart failure is less common. Genetic counseling is indicated in patients with asymmetric septal hypertrophy, which appeared during the growth period at pubertal age.

Treatment is directed primarily to pathological diastolic relaxation. B-blockers and slowing heart rate calcium channel blockers with a slight vasodilating effect (eg, verapamil) as monotherapy or in combination form the basis of therapy. Reducing myocardial contractility, these drugs extend the heart. Slowing down the heart rate, they increase the diastolic period of filling. Both effects reduce obstruction of the vestibular tract, thus improving the diastolic function of the ventricle. In severe cases, you can add disopyramide, given its negative inotropic effect.

Preparations that reduce preload (for example, nitrates, diuretics, ACE inhibitors, APA II), reduce the size of the heart chambers and aggravate the symptoms of hypertrophic cardiomyopathy. Vasodilators increase the gradient of the outflow tract and cause reflex tachycardia, which subsequently worsens the diastolic function of the ventricle. Inotropic drugs (eg, cardiac glycosides, catecholamines) exacerbate obstruction of the outflow path without decreasing the high end-diastolic pressure, which can cause arrhythmias.

In the event of fainting, sudden cardiac arrest, and if the arrhythmia is confirmed by ECG or 24-hour outpatient monitoring, it is necessary to consider the implantation of a cardioverter-defibrillator or antiarrhythmic therapy. Patients with hypertrophic cardiomyopathy are recommended antibiotic prophylaxis of infective endocarditis. Participation in sports is contraindicated, since many cases of sudden death occur during an increased load.

Treatment in the phase of expansion and stagnation in hypertrophic cardiomyopathy is conducted in the same way as treatment of hypertrophic cardiomyopathy with predominant systolic dysfunction.

If septal hypertrophy and obstruction of the outflow path cause significant symptoms, despite medical treatment, surgical intervention is necessary. Catheter ablation with ethyl alcohol is not always effective, but it is increasingly used. Surgical septal myotomy or myomectomy reduces symptoms more reliably, but does not increase life expectancy.