It is defined at different ages and can denote both physiological and pathological conditions. The severity of clinical symptoms involves the choice of treatment tactics. Untreated abnormal tachycardia may pose a risk to human health.
The term "tachycardia" is similar to the ancient Greek and is referred to as "fast" and "heart". The first references to historical records of this condition were documented by the date 1862, when Peter Ludwig Panum described the ventricular tachycardia that arose during his experiment in the introduction of fat into coronary vessels. In 1909, Lewis identified this as a result of myocardial ischemia after studying this phenomenon. But on the electrocardiogram it was possible to fix ventricular tachycardia, which developed on the background of a myocardial infarction, only in 1921.
Tachycardia should be understood as the accelerated work of the heart, which determines more than the upper threshold of the age norm (in adults it is more than 100 beats per minute).The heart rate in such cases may be disturbed or remain normal, that is, sinus.
In modern medicine, the term "tachycardia" denotes a specific symptom that can be observed in a variety of diseases.Most often, the tachycardia develops when the autonomic nervous system works disorder, and an increased frequency of heart rate is observed in endocrine diseases and various hemodynamic disorders. A separate place is occupied by tachycardias in the group of arrhythmias, where they are defined as sinus, paroxysmal, ventricular tachycardia.
Mechanisms of tachycardia development
To understand what a tachycardia is, one should go a little bit into the processes of its occurrence. By the end of the twentieth century two mechanisms of autowave nature involved in the development of tachycardia were precisely established:
1. Re-entry or recirculatory excitement, which has been proven to be the basis for the development of such a tachycardia, as nodular or supra-ventricular.
Efrimov and other American researchers studied nodal tachycardia and were able to demonstrate its association with the heterogeneous distribution of connective tissue in the AV node. Moreover, these processes are defined as congenital and are characteristic of most people.
2. Increase spontaneous activity of the heart muscle (myocardium). At the end of the twentieth century, this process was considered as a chaotic behavior of excitation vortices in the heart muscle.
It is already known today that fibrillation occurs due to the appearance of reverberators - autowave vortices in a two-dimensional active medium that can increase in its quantity. Their origin and reproduction were studied by many groups of scientists for more than 10 years, and in the late 1970s, the reproduction of reverb cells in the heart muscle was experimentally confirmed.
The main symptoms of tachycardia
- Sudden onset of an attack of a rapid heartbeat. If pathological impulses follow from the atrium, then the heart rate may be 200-350 beats / min, with a ventricular tachycardia, then 150-200 beats per minute.
- At the neck is a pulsed carotid artery that can be felt.
- An attack can last for several seconds or take a few days.
An electrocardiogram always identifies the following ECG signs of tachycardia to clarify the diagnosis:
- Supraventricular tachycardia - ventricular complexes (QRS) are unchanged, while the teeth P and T merge.
- Ventricular tachycardia - QRS complexes have been altered in their form, amplitude, or alternation.
Than dangerous tachycardia
In the course of heart failure, insufficient blood flow to the ventricles occurs, resulting in a reduction in cardiac output.This indicator is diagnosed using echocardiography and is a sign of heart failure.
Pronounced tachycardia or frequent heart attacks can contribute to the development of the following serious complications:
- loss of creation;
- arterial hypotension;
- myocardial ischemia;
- aggravation of already existing heart failure with the development of edema.
Ventricular tachycardia under predisposing conditions can pass into ventricular fibrillation. Such a condition is critical and requires immediate medical intervention.
Pathological tachycardia: causes of development
Earlier, it was believed that a number of diseases may be the main cause of the development of a rapid heartbeat. But recently, scientists increasingly pay attention to the emergence of tachycardia due to a disorder of some autowave heart function. As a result, a number of diseases, which are often combined with tachycardia, are considered only as conditions contributing to the disorder of this new link of cardiac activity (autofocus heart function).
Common pathologies that cause tachycardia:
- Organic damage to the heart muscle (myocardium) - is combined with tachycardia in 95% of cases. 70% of ventricular tachycardia accounts for chronic CHD. Another 1-2% are associated with myocardial infarction. Other organic heart disease accompanied by tachycardia is hypertonia, cardiomyopathy, heart disease, myocarditis.
- Intoxication with cardiac glycosides is 20% of the total amount of tachycardia in the ventricular form.
- Other diseases not related to the cardiovascular system, but often causing tachycardia, are: rheumatism, pheochromocytoma, autonomic disorders, emotional experiences, cardiac catheterization, surgical interventions on the myocardium.
Types of tachycardia
The main two divisions of the tachycardia are physiological and pathological. The first one is often determined by clinically healthy people and is not a cause for concern. The physiological reactions of the body contribute to the increase in the frequency of heart contractions during exercise or during excitement. Such a tachycardia does not cause the patient discomfort and is able to independently pass in a calm condition.
Pathological tachycardia is divided into several forms, which are most often observed in adults, children, pregnant women. These are sinus tachycardia, paroxysmal tachycardia, ventricular tachycardia (or ventricular fibrillation). Each of them has the features of the clinical course, is able to reduce the quality of life of the patient to a greater or lesser extent.
Normally, the rhythm of the heart is controlled by a sinus node located in the right atrium. With sinus tachycardia, the generation of electrical impulses or their transmission from the sinus node to the ventricles is disturbed. As a result, the heart rate is increased and in adults is more than 100 beats per minute.
Sinus tachycardia is often determined by physical stress and emotional experiences. In such cases, it is not considered clinically unfavorable, therefore, it does not cause any concern.
Pathological sinus tachycardia is often preserved in rest. It is often caused by extracardiac factors (fever, anemia, thyroid disease, blood loss, respiratory failure, and more rarely a sign of a deterioration in the general condition of the patient with cardiac pathology: chronic heart failure, cardiomyopathy, acute myocarditis, myocardial infarction.
A complicated disease, characterized by a sudden onset and the same end of an attack, during which the heart rate increases from 150 to 300 beats / min. Depending on the localization of the pathological focus, the atrial, nodal and ventricular paroxysmal tachycardia are distinguished.
The supraventricular form of paroxysmal tachycardia occurs in most cases against the background of overexcitation of the sympathetic department of the autonomic nervous system, whereas the ventricular form often accompanies complex organic heart disease.
It is determined in 85% of cases in patients with myocardial infarction, and among men it is several times more often than among women. To a lesser extent, the damage occurs on the background of cardiomyopathies, heart failure and only in 2% of patients without a history of cardiovascular disease.
Fibrillation of the ventricles
A terminal condition that often develops as a result of transmural myocardial infarction. It is also a complication of other organic heart diseases - myocarditis, cardiomyopathy, heart failure.
For the first time, the term ventricular fibrillation was used in 1874 by Vulpian, while the first electrocardiogram was published in August 19200 by Augustus Hoffman.
The classification of ventricular fibrillation is still not fully recognized by all. Most often the following forms of PF are isolated, such as primary, secondary, later. The primary differs from secondary ventricular fibrillation by the absence of left ventricular insufficiency and the development of acute ischemia. Both forms develop during the first 48 hours after myocardial infarction. Late fibrillation of the ventricles is determined two days after the heart attack, most often it develops for 2-4 weeks of the disease.
From the beginning of fibrillation to the onset of clinical death, 2-3 minutes pass, and in this period of time assistance should be provided in the form of defibrillation.
Complications with tachycardia
The most terrible complication is clinical death, which develops when fibrillation of the ventricles. It is also possible to develop the following pathological conditions:
- loss of consciousness;
- progression of chronic heart failure.
Nodjulyatochkovaya and sinusnaya tachycardia are rarely complicated. If this happens, then the course of the underlying disease worsens.
Thus, tachycardia, as a symptom and as a separate form of arrhythmia, occurs quite often. It can be both physiological and pathological. Paroxysmal and ventricular tachycardia is considered to be particularly unfavorable. It is important in such cases to assist the patient in a timely manner in order to prevent a fatal outcome.