Arrhythmia

According to the causes and mechanism of arrhythmia, they are conditionally divided into two categories: those related to cardiac pathology (organic) and those not related to it (inorganic or functional). The group of functional arrhythmias includes neurogenic, diselectrolytic, iatrogenic, mechanical and ideopathic rhythm disturbances.

1. Various forms of organic arrhythmias and blockades are frequent companions of cardiac pathologies: coronary artery disease, myocarditis, cardiomyopathy, malformations and injuries of the heart, heart failure, as well as complications of cardiac surgery.
2. The development of sympath-dependent arrhythmias is facilitated by excessive activation of the tone of sympathetic NS under the influence of stress, strong emotions, intense mental or physical work, smoking, alcohol consumption, strong tea and coffee, spicy food, neurosis, etc. Activation of sympathetic tone is also caused by thyroid diseases (thyrotoxicosis), intoxication, fever, blood diseases, viral and bacterial toxins, industrial and other intoxications, hypoxia. Women suffering from premenstrual syndrome may experience sympatho-dependent arrhythmias, heart pain, and feelings of suffocation.
3. Vago-dependent neurogenic arrhythmias are caused by activation of the parasympathetic system, in particular, the vagus nerve. Vago-dependent rhythm disturbances usually develop at night and can be caused by diseases of the gallbladder, intestines, peptic ulcer of the duodenum and stomach, diseases of the bladder, in which the activity of the vagus nerve increases.
4. Diselectrolytic arrhythmias develop with electrolyte imbalance disorders, especially magnesium, potassium, sodium and calcium in the blood and myocardium.
5. Iatrogenic rhythm disturbances occur as a result of the arrhythmogenic effect of certain medications (cardiac glycosides, beta-blockers, sympathomimetics, diuretics, etc.).
6. The development of mechanical arrhythmias is facilitated by chest injuries, falls, shocks, electric shock, etc.
7. Idiopathic arrhythmias are considered rhythm disturbances without an established cause. Hereditary predisposition plays a role in the development of arrhythmias.

Rhythmic sequential contraction of the heart is provided by special muscle fibers of the myocardium, which form the conducting system of the heart. In this system, the driver of the rhythm of the first order is the sinus node: it is in it that excitation originates with a frequency of 60-80 times per minute. Through the myocardium of the right atrium, it spreads to the atrioventricular node, but it turns out to be less excitable and gives a delay, so the atria first contract and only then, as the excitation spreads through the Gis bundle and other parts of the conducting system, the ventricles.

Thus, the conducting system provides a certain rhythm, frequency and sequence of contractions: first the atria, and then the ventricles. The defeat of the conducting system of the myocardium leads to the development of rhythm disturbances (arrhythmias), and its individual links (atrioventricular node, bundle or Gis legs) - to conduction disturbances (blockades). In this case, the coordinated work of the atria and ventricles may be sharply disrupted.

The development of organic arrhythmias is based on damage (ischemic, inflammatory, morphological) to the heart muscle. They make it difficult for the normal propagation of an electrical impulse through the conducting system of the heart to its various departments. Sometimes the damage also affects the sinus node – the main driver of the rhythm. During the formation of cardiosclerosis, scar tissue interferes with the conduction function of the myocardium, which contributes to the occurrence of arrhythmogenic foci and the development of conduction and rhythm disorders.

The etiological, pathogenetic, symptomatic and prognostic heterogeneity of arrhythmias causes discussions about their unified classification. According to the anatomical principle, arrhythmias are divided into atrial, ventricular, sinus and atrioventricular. Taking into account the frequency and rhythmicity of heart contractions, it is proposed to distinguish three groups of rhythm disorders:

• bradycardia,
• tachycardia (palpitations of more than 90 beats . in min.),
• bradycardia (reduced heartbeat less than 60 beats. in min.),
• arrhythmias: extrasystole (extraordinary cardiac contractions), atrial fibrillation (chaotic contractions of individual muscle fibers).

The most complete classification is based on the electrophysiological parameters of rhythm disturbance, according to which arrhythmias are distinguished:

I. Caused by a violation of the formation of an electric pulse. This group of arrhythmias includes nomotopic and heterotopic (ectopic) rhythm disturbances.

Nomotopic arrhythmias are caused by a violation of the automatism function of the sinus node and include sinus tachycardia, bradycardia and arrhythmia. Separately, sinus node weakness syndrome (SSS) is distinguished in this group.

Heterotopic arrhythmias are characterized by the formation of passive and active ectopic complexes of myocardial excitation located outside the sinus node.

In passive heterotopic arrhythmias, the occurrence of an ectopic pulse is caused by a slowdown or disruption of the main pulse. Passive ectopic complexes and rhythms include atrial, ventricular, atrioventricular junction disorders, migration of the supraventricular pacemaker, popping contractions.

With active heterotopias, the resulting ectopic pulse excites the myocardium before the pulse formed in the main driver of the rhythm, and ectopic contractions "interrupt" the sinus rhythm of the heart. Active complexes and rhythms include: extrasystole (atrial, ventricular, originating from the atrioventricular junction), paroxysmal and nonparoxysmal tachycardia (originating from the atrioventricular junction, atrial and ventricular forms), fluttering and flickering (fibrillation) of the atria and ventricles.

II. Arrhythmias caused by impaired intracardiac conduction function. This group of arrhythmias occurs as a result of a decrease or cessation of the propagation of the pulse through the conducting system. Conduction disturbances include:

• sinoatrial blockade;
• intra - atrial blockade;
• atrioventricular blockade (I, II and III degrees);
• syndromes of premature ventricular arousal;
• intraventricular blockades of the legs of the Gis bundle (one-, two- and three-bundle).

III. Combined arrhythmias. Arrhythmias that combine conduction and rhythm disorders include:

• ectopic rhythms with exit blockade;
• parasystole;
• atrioventricular dissociations.

The manifestations of arrhythmias can be very different and are determined by the frequency and rhythm of heart contractions, their effect on intracardiac, cerebral, renal hemodynamics, as well as the function of the myocardium of the left ventricle. There are so-called "mute" arrhythmias that do not manifest themselves clinically. They are usually detected by physical examination or electrocardiography.

The main manifestations of arrhythmias are palpitations or a feeling of interruptions, fading when the heart is working. The course of arrhythmias may be accompanied by suffocation, angina, dizziness, weakness, fainting, and the development of cardiogenic shock. Palpitations are usually associated with sinus tachycardia, attacks of dizziness and fainting – with sinus bradycardia or sinus node weakness syndrome, cardiac arrest and discomfort in the heart area – with sinus arrhythmia.

With extrasystole, patients complain of feelings of fading, pushing and interruptions in the work of the heart. Paroxysmal tachycardia is characterized by suddenly developing and stopping heart palpitations up to 140-220 beats. in min. The sensation of a frequent, irregular heartbeat is noted with atrial fibrillation.

The course of any arrhythmia can be complicated by fibrillation and fluttering of the ventricles, which is equivalent to stopping blood circulation, and lead to the death of the patient. Already in the first seconds, dizziness, weakness develop, then loss of consciousness, involuntary urination and convulsions. Blood pressure and pulse are not determined, breathing stops, pupils dilate – a state of clinical death occurs. In patients with chronic circulatory insufficiency (angina pectoris, mitral stenosis), shortness of breath occurs during paroxysms of tachyarrhythmia and pulmonary edema may develop.

With complete atrioventricular blockade or asystole, syncopal states may develop (Morgagni-Adams-Stokes attacks characterized by episodes of loss of consciousness) caused by a sharp decrease in cardiac output and blood pressure and a decrease in blood supply to the brain. Thromboembolic complications with atrial fibrillation in every sixth case lead to a cerebral stroke.

The primary stage of the diagnosis of arrhythmia can be carried out by a therapist or a cardiologist. It includes the analysis of patient complaints and the determination of the peripheral pulse characteristic of cardiac arrhythmias. At the next stage, instrumental non-invasive (ECG, ECG monitoring), and invasive (NPEFI, VEI) research methods are carried out:

• Electrocardiogram. It records the heart rate and frequency for several minutes, so only permanent, stable arrhythmias are detected through an ECG. Rhythm disturbances of a paroxysmal (temporary) nature are diagnosed by the Holter daily ECG monitoring method, which registers the circadian rhythm of the heart.
• Ultrasound of the heart. To identify the organic causes of arrhythmia, Echo-KG and stress Echo-KG are carried out.
• Invasive diagnostic methods. They allow artificially causing the development of arrhythmia and determining the mechanism of its occurrence. During intracardiac electrophysiological examination, catheter electrodes are brought to the heart, registering an endocardial electrogram in various parts of the heart. The endocardial ECG is compared with the result of recording an external electrocardiogram performed simultaneously.
• Load tests. Tilt test is performed on a special orthostatic table and simulates conditions that can cause arrhythmia. The patient is placed on a table in a horizontal position, the pulse and blood pressure are measured and then, after administration of the drug, the table is tilted at an angle of 60-80 ° for 20 to 45 minutes, determining the dependence of blood pressure, heart rate and rhythm on changes in body position.
• CHPEFI. Using the method of transesophageal electrophysiological examination (cHpEFI), electrical stimulation of the heart is carried out through the esophagus and a transesophageal electrocardiogram is recorded, which records the heart rate and conductivity.
• Other methods. A number of auxiliary diagnostic tests include load tests (step tests, squat tests, marching, cold, etc. tests), pharmacological tests (with isoproterinol, with dipyridomol, with ATP, etc.) and are performed for the diagnosis of coronary insufficiency and the possibility of judging the relationship of the load on the heart with the occurrence of arrhythmias.

Conservative therapy

The choice of therapy for arrhythmias is determined by the causes, type of rhythm and conduction disorders of the heart, as well as the patient's condition. In some cases, it is enough to treat the underlying disease to restore the normal sinus rhythm.

Sometimes, special medication or cardiac surgery is required to treat arrhythmias. The selection and appointment of antiarrhythmic therapy is carried out under systematic ECG control. According to the mechanism of action , there are 4 classes of antiarrhythmic drugs:

• Class 1 - membrane stabilizing drugs that block sodium channels;
• 1A - increase the repolarization time;
• 1B - reduce repolarization time;
• 1C - do not have a pronounced effect on repolarization;
• Class 2 - beta-blockers;
• Class 3 - lengthen repolarization and block potassium channels;
• Class 4 - block calcium channels.

Surgical treatment

Non-drug treatments for arrhythmias include electrocardiostimulation, implantation of a cardioverter defibrillator, radiofrequency ablation and open-heart surgery. They are performed by cardiac surgeons in specialized departments.

Implantable antiarrhythmic devices. Implantation of an electrocardiostimulator (EX) – an artificial pacemaker is aimed at maintaining a normal rhythm in patients with bradycardia and atrioventricular blockades. The implanted cardioverter-defibrillator for preventive purposes is sewn to patients who have a high risk of sudden occurrence of ventricular tachyarrhythmia and automatically performs pacing and defibrillation immediately after its development.

Radiofrequency ablation. With the help of the RF of the heart, through small punctures with the help of a catheter, cauterization of the area of the heart generating ectopic impulses is carried out, which allows blocking impulses and preventing the development of arrhythmia.

Open operations. Open-heart surgery is performed for cardiac arrhythmias caused by left ventricular aneurysm, heart valve defects, etc.

In prognostic terms, arrhythmias are extremely ambiguous. Some of them (supraventricular extrasystoles, rare ventricular extrasystoles), not related to organic pathology of the heart, do not pose a threat to health and life. Atrial fibrillation, on the contrary, can cause life-threatening complications: ischemic stroke, severe heart failure. The most severe arrhythmias are fluttering and ventricular fibrillation: they pose an immediate threat to life and require resuscitation.

The main direction of prevention of arrhythmias is the treatment of cardiac pathology, which is almost always complicated by a violation of the rhythm and conduction of the heart. It is also necessary to exclude extracardial causes of arrhythmia (thyrotoxicosis, intoxication and feverish states, autonomic dysfunction, electrolyte imbalance, stress, etc.). It is recommended to limit the intake of stimulants (caffeine), the exclusion of smoking and alcohol, self-selection of antiarrhythmic and other drugs.