Paroxysmal tachycardias (PT) are heart rhythm disturbances that occur in paroxysms and are characterized by a high heart rate (140-200 per minute or more) and a relatively regular rhythm. They refer to active heterotopic arrhythmias originating from an ectopic focus of excitation, which is superior in activity to the sinus node. Depending on the place of their occurrence, it is customary to distinguish supraventricular and ventricular paroxysmal tachycardias.
Causes and mechanisms of occurrence
Supraventricular paroxysmal tachycardia
This group of pathological conditions includes rhythm disturbances, the source of which may be the sinus node, atria, and atrioventricular junction. Their prevalence in the population is low. In clinical practice, they are usually divided into atrial and atrioventricular.
A distinctive feature of supraventricular paroxysmal arrhythmias is the presence of unchanged ventricular complexes on the electrocardiogram. However, if intraventricular conduction is disturbed, they can be dilated, and it is difficult to differentiate them from ventricular arrhythmias.
In most cases, arrhythmias of this type are detected in individuals without established organic heart damage. They arise against the background:
changes in hormonal levels;
excessive consumption of alcohol, coffee;
Atrial paroxysmal tachycardias are heterogeneous in genesis, clinical course and ECG manifestations , therefore, several types are distinguished among them:
sinus paroxysmal (begins suddenly with an atrial extrasystole; P waves are recorded before each QRS complex; the average frequency is 120-140 per minute; characterized by short paroxysms that stop on their own);
slow focal (typically slow onset with the so-called warm-up without extrasystoles with a characteristic increase in frequency to 110-140 beats per minute and the same gradual extinction of the attack; verapamil or -blockers are used for treatment);
fast focal (develops against the background of organic lesions, hypokalemia, VSD; proceeds at a frequency of up to 200 per minute and can disrupt hemodynamics; vegetative tests, antiarrhythmics or electrical impulse therapy are used for relief);
multifocal (occurs in elderly patients with cor pulmonale, with sepsis, intoxication with cardiac glycosides; the ECG determines a frequency of 200 per minute, P waves of different amplitude and polarity, different duration of the PQ interval; accompanied by severe disorders of systemic circulation and may be a harbinger of ventricular fibrillation; -blockers, amiodarone, calcium antagonists are used for treatment).
With paroxysmal tachycardia arising from the atrioventricular junction, the ECG resembles that of the atrial arrhythmia, but differs from it in the direction and location of the P wave, which is always negative, located in front of or behind the ventricular complex (or merges with it), which depends on features of retrograde conduction of excitation to the atria.
The pathological substrate of this type of tachycardia is the presence of main and additional conduction pathways in the atrioventricular node – explicit, as in WPW syndrome, or hidden. In some patients, paroxysms of arrhythmias occur by the mechanism of the repeated course of the wave without the participation of additional pathways.
If the impulse from the atria to the ventricles propagates through the normal pathways, then a tachycardia chain is recorded on the film, consisting of QRS complexes normal in width and shape, if the excitation spreads along additional paths, then they are deformed and widened.
Ventricular paroxysmal tachycardia
Paroxysmal ventricular tachycardias are among the severe life-threatening rhythm disturbances, since they not only disrupt hemodynamics, but can also turn into ventricular fibrillation. Their source is the bundle of His, Purkinje fibers or ventricular myocardium. In all types of such tachycardias, common features can be distinguished:
wide deformed ventricular complexes (more than 0.12 s);
atrioventricular dissociation, that is, an inconsistent contraction of the atria and ventricles;
heart rate 140-220 beats per minute.
In clinical practice, the following types of ventricular paroxysmal tachycardia are distinguished:
bidirectional (correct alternation of QRS complexes of various shapes, emanating from different foci);
“Pirouette” (unstable, characterized by a wave-like increase and decrease in the amplitude of the ventricular complexes);
Ventricular PTs are more common in patients with organic heart disease. Most of them are based on the re-entry mechanism.
It should be noted that there are rare genetically determined diseases in which ventricular tachycardia is the main clinical sign. The most common among them are:
syndrome of long QT interval (pathology of the protein of potassium or sodium channels; manifests in childhood tachycardia of the “pirouette” type; the risk of sudden death reaches 70%);
syndrome of a shortened QT interval (a defect in the potassium channel gene; manifests itself from childhood with atrial fibrillation, paroxysmal ventricular tachycardia);
arrhythmogenic right ventricular dysplasia (replacement of the right ventricular myocardium with adipose tissue; characterized by progressive heart failure and severe arrhythmias);
Brugada syndrome (hereditary defect of sodium channels; right bundle branch block, pirouette-type PT, high risk of sudden death).
Normally, a person does not feel the work of the heart. In some cases, he is not aware of the rhythm disturbances that he has. The onset of an attack of paroxysmal tachycardia is usually regarded by patients as a shock in the chest, after which there is:
- feeling palpitations ;
- compression behind the sternum;
- shortness of breath ;
- feeling of fear.
An objective examination also reveals pathological signs:
- pallor of the skin;
- swelling and pulsation of the cervical veins;
- frequent pulse of reduced filling;
- increased sonority of heart sounds;
- lowering blood pressure, etc.
Short paroxysms of supraventricular PT do not lead to hemodynamic disturbances. With a prolonged attack, the general condition depends on the initial state of the myocardium and the presence of concomitant diseases. In patients with organic pathology, such an attack causes:
- decrease in minute and stroke blood volume;
- drop in blood pressure ;
- violation of perfusion of vital organs.
With inadequate blood supply to the brain tissue, fainting, transient ischemic attacks occur, with a decrease in the intensity of coronary blood flow, myocardial ischemia develops.
Paroxysmal ventricular tachycardia leads to more severe hemodynamic disorders, the development of arrhythmogenic shock and loss of consciousness. This significantly increases the risk of sudden death.
Diagnosis of paroxysmal tachycardia is based on assessing the severity of symptoms, identifying its relationship with arrhythmia and recording the arrhythmia itself on an electrocardiogram. At the same time, a standard ECG is not always informative. In order to fix an arrhythmia attack, Holter monitoring is usually used. With relatively rare episodes of arrhythmia, it is advisable to use long-term monitoring with the inclusion of ECG recording according to indications.
At the next stage, echocardiography is prescribed to the patient to detect organic heart damage and assess the functional state of the myocardium .
In order to elucidate the mechanism of supraventricular paroxysmal tachycardia, such patients undergo an electrophysiological study.
Reflex, medication, electrical and surgical methods can be used to treat paroxysmal tachycardia. The choice of patient management tactics is carried out taking into account the clinical situation created by an attack of arrhythmia and the underlying disease. Regardless of the category of arrhythmia, all patients are prescribed etiotropic treatment, if possible.
To eliminate the paroxysms of many supraventricular PTs, vegetative tests are successfully used:
straining with holding the breath after taking a deep breath;
pressure on the eyeballs (within 5 seconds);
swallowing a large lump of food;
irritation of the mucous membrane of the pharynx before the appearance of the gag reflex;
lowering the face into cold water;
massage of the carotid sinus;
If these measures are ineffective, medications are prescribed:
Parenteral administration of drugs is preferred. In addition to the introduction of antiarrhythmic drugs into the body, it is prescribed:
- oxygen therapy;
- metabolic therapy;
- taking sedatives ;
- correction of electrolyte disturbances is performed;
- the coronary blood flow is optimized.
If the attack could not be stopped, then they resort to electrical methods – electrical impulse therapy.
In the future, after the restoration of sinus rhythm, such patients are recommended examination and long-term drug therapy. Its purpose is to prevent seizures.
With ventricular PT, vagal tests do not stop the attack and do not slow down the heart rate. In such cases, drug therapy is used to suppress paroxysm:
- less often – other antiarrhythmics (lidocaine, propafenone, etacizin, etc.).
However, the choice of the method of treatment in this case depends on the nature of the arrhythmia and the assessment of the prognosis.
With paroxysms of ventricular tachycardia, which are accompanied by severe hemodynamic disturbances, electrical cardioversion is considered the means of choice.
Of the surgical methods for the treatment of paroxysmal tachycardia, radiofrequency ablation and implantation of an artificial cardioverter-defibrillator can be used.
Which doctor to contact
If you suspect attacks of rhythm disturbances, you should consult a cardiologist. Additionally, you may need to consult an endocrinologist, gastroenterologist, geneticist. The patient is assigned an examination at the Department of Functional Diagnostics. In case of severe rhythm disturbances, consultation with a cardiac surgeon is necessary.
The prognosis for paroxysmal tachycardia is determined by its form, the frequency of paroxysms, the nature and severity of the underlying disease. With organic lesions, it is more serious and carries a high risk of sudden death. Such patients should be constantly monitored by a cardiologist and receive appropriate therapy.