AV-nodal tachycardia mechanism of occurrence clinic diagnosis and ECG treatment

Supraventricular arrhythmias are quite common, often recur, sometimes persist, but rarely life-threatening. Among all cases of cardiological pathology, 6-10% are nodal tachycardia, which is also called supraventricular (SVT) or supraventricular variant.

With a normal rhythm, all sections of the heart (atria, then the ventricles) are synchronously sequentially reduced at a frequency of 60-90 per minute.

Supraventricular tachycardia is an attack of rapid heart rate that suddenly arises and disappears. During an attack, the heart contracts rhythmically with a frequency (160-240 beats / min). SVT belongs to the general group of arrhythmias and is often associated with diseases of the cardiovascular system. In fact, this is a series of monotonous extrasystoles that go continuously one by one.

The mechanism of paroxysmal development of nodal tachycardia is close to the mechanism of extrasystole development. Impulses during an attack do not occur in the sinoatrial junction, but in the atrioventricular node.

Arrhythmia is a rhythm that differs from normal (normal rhythm is the appearance of impulses in the sinus node, the presence of P wave on the ECG, the sequence of excitation of the heart at a frequency of 60-90 beats / min).

Supraventricular arrhythmias are quite common, often recurring, sometimes persistent and rarely life-threatening. The frequency of their occurrence depends on age, gender, concomitant pathology.

The appearance of paroxysm is affected by a number of factors:

  • Age;
  • Gender (women get sick twice as often);
  • Duration of cardiovascular disease (SVT is accompanied by greater heart rate and is more often the cause of hospitalization);

Paroxysmal tachycardia is of functional and organic origin.

Provoking factors of SVT of functional genesis (30-70% of cases):

  • Physical and psycho-emotional overload;
  • The abuse of caffeine, nicotine;
  • A sharp change in body position;
  • Frequent breathing;
  • Reflex reactions in biliary and renal colic;
  • Osteochondrosis of the cervical spine;
  • Lesions of the esophageal diaphragm;
  • Hormonal imbalance (menstruation, pregnancy, menopause, puberty);

SVT of organic origin occurs when:

  • Myocardial infarction;
  • Postinfarction, diffuse cardiosclerosis, myocardiofibrosis;
  • Angina pectoris;
  • Arterial hypertension;
  • Acquired and congenital heart defects;
  • Cardiomyopathies;
  • WPW Syndrome;
  • An overdose of digitalis, adrenergic agonists, beta-adrenostimulants;
  • Hypokalemia, hypomagnesemia, metabolic ac >

Depending on the pathogenetic basis of development, they share:

Re-entry, or secondary entry, excitation waves. The most common mechanism for the development of paroxysm due to the circular circulation of impulses in the myocardial conduction system.

For its occurrence, 4 nuances are needed: two paths, blocking one of them, a delay in the passage of the pulse along the second path, and the reverse excitation current along the previously blocked path.

The re-entry circle can form in a person with an anatomical substrate (additional pathways, AV dissociation – macrore-entry) or functional myocardial heterogeneity (microre-entry).

  • Ectopic automatism is a natural property of myocytes of a specialized conducting system in the diastole (spontaneous diastolic depolarization) to generate pulses (in the sinus or AV nodes, atria) of high frequency.
  • Trigger mechanism. Under certain conditions caused by a decrease in the potential for calm, neurons of the conduction system and myocardium acquire the property of spontaneous activity due to residual potentials that cause single or repeated excitation of neurons in response to previous depolarization.
  • Classification of supraventricular tachycardia:

    1. Sinoatrial;
    2. Atrial
    3. AV nodal tachycardia;
    4. AV nodal reciprocal tachycardia with the presence of additional pathways (WPW syndrome).

    Paroxysm of SVT has a clearly defined start and a sharp end to the attack. The patient feels a push in the area of ​​the heart, which immediately passes into a rapid heartbeat. Sometimes, precursors may occur before an attack: unpleasant sensations and interruptions in the work of the heart, dizziness, tinnitus.

    • Vertigo, loss of consciousness (cerebral ischemia);
    • Autonomic dysfunction (trembling limbs, weakness, cold sweat, increased diuresis);
    • Shortness of breath (with a decrease in blood circulation in a small circle), cough;
    • Feeling of ripple in the head and neck

    During an attack, heart rate accelerates to 160-240 beats / min.

    Diagnosis of SVT is based on ECG results:

    1. The correct rhythm, heart rate 160-240 per minute;
    2. QRS complexes are practically unchanged;
    3. The presence of a P wave, positive or negative, is superimposed on the QRS complex, located before or after ORS.

    A protracted attack of atrioventricular nodal reciprocal tachycardia can be complicated by:

    • Acute circulatory failure;
    • Arrhythmogenic shock;
    • ACS, myocardial infarction;
    • Cerebral ischemia.

    After a final diagnosis is made on the basis of ECG data and clinical criteria, urgent as well as planned treatment should be started.

    Emergency care algorithm for SVT with stable hemodynamics:

      Non-drug methods. Under the condition of stable hemodynamic parameters in a patient, methods are used to stop paroxysm aimed at stimulating N.vagus, slowing down the AV connection. The use of vagal samples is prohibited if there are signs of development of the BODY, ACS, pregnancy.

    • breath holding
    • forced cough;
    • Valsalva test (sharp tension at the height of inspiration);
    • provocation of the gag reflex by irritation of the root of the tongue;
    • swallowing solid food;
    • dipping in ice water;
    • massage of the carotid sinus (if there is no cerebral blood flow insufficiency).
  • Adenosine 6 mg iv in a bolus (1-3 seconds), after 2 minutes you can enter another 12 mg, if necessary, the next dose of 12 mg.

    Verapamil with adenosine inefficiency – with a dosage of 2,5-5 mg in 2 minutes. followed by transfer to the oral form of 240 mg / day.

  • The use of sedatives: triazolam 0,125-0,25 mg, alprazolam 0,25 mg, lorazepam 1 mg.
  • With insufficient effectiveness – procainamide 1000 mg iv in 20 minutes, digoxin, proranolol, propafenone, flecainide, amiodarone.
  • If hemodynamic parameters are unstable during SVT, the phenomena of circulatory failure increase, the patient immediately undergoes synchronized cardioversion (EIT).

    Indications for surgical correction of SVT (destruction of auxiliary pathways, ectopic foci of automatism) with the ineffectiveness of medications:

    • Heart rate of more than 200 per minute;
    • Hemodynamic complications in SVT;
    • Young age;
    • The presence of an auxiliary route, atrial fibrillation.

    conclusions

    SVT are intermediate between potentially fatal and benign arrhythmias.

    Patients with debut paroxysm of tachycardia need to be examined in a specialized hospital in order to differentiate the type of CBT, exclude heart disease, and determine further treatment tactics.

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    Reciprocal tachycardia

    Reciprocal tachycardia (in another way – paroxysmal or AV-nodal) refers to a disease in which the heartbeat increases in areas of the heart that inhibit the transmission of an electrical impulse. It often occurs at a young age (mainly in women), but does not bear the danger of death. However, serious complications may occur.

    Reciprocal tachycardia is characterized not only by increased heart rate, but also significant dizziness, signs of suffocation. The patient’s performance decreases, the psycho-emotional background is disturbed.

    Nodal tachycardia is in the contours of the repeated inputs of excitation, which are formed by fast and slow paths. Most often, this excitation along the slow paths extends from the atrium to the ventricle in the antegrade manner, and along the fast paths – retrograde. The reason is atrial (PE) or ventricular (PVC) extrasystole.

    So, PE helps to block the antegrade conduction of impulses along fast paths, so they propagate along slow ones. But back from the ZhE, excitation is carried out only along the fast paths.

    And only in rare cases, ventricular extrasystole can be carried out in a retrograde manner along the fast paths to the atrium, and return back along the slow.

    Heart palpitations may stop when the slow path is blocked. At the same time, the contours of the reentrances do not affect the ventricles. Therefore, in reciprocal tachycardia, AV dissociation occurs. The legs of the bundle of His are also blocked. The peculiarity is that the contractile frequency in the atrium does not change, but in the ventricles decreases.

    The concept of “reciprocal” stands for “opposite,” because the electrical impulses are in the wrong direction. The disease is included in the group of supraventicular tachycardia, which indicates relative safety.

    But there are also acquired forms of paroxysmal reciprocal tachycardia, due to the following reasons:

    • powerful stressful situations;
    • smoking for many years;
    • abuse of alcoholic beverages;
    • physical activity;
    • excessive amounts of coffee drunk per day.

    After lengthy research and observation of patients, it was proved that the development of this type of tachycardia is more associated with disorders of the nervous system. So, the symptomatology begins to manifest itself intensely after the patient is nervous and overexcited emotionally.

    Pathology proceeds with the following symptoms:

    • heart palpitations;
    • dyspnea;
    • pain in the chest and heart;
    • dizziness;
    • general weakness;
    • bouts of lack of oxygen;
    • in rare cases, loss of consciousness.

    The feature of the signs is that the attack stops after the patient holds his breath.

    Diagnosis of reciprocal tachycardia is carried out in conjunction with biochemical analyzes and special medical devices. In general, the survey is conducted as follows:

    • At the initial treatment, the specialist collects an anamnesis, listens to the patient’s complaints. At the same time, the type of work activity, the presence of pathologies in the family are specified.
    • Next, a visual inspection is carried out. It includes the determination of changes in complexion, dermatological formations on the skin and nails. After the doctor examines the heart and lungs (the presence of noise and wheezing).
    • A general blood and urine test is prescribed, which determines the percentage of cholesterol, sugar and potassium.
    • After the tests, hardware diagnostics are carried out, which includes an ECG – studies of changes in heartbeat.
    • HMEGG – the definition of the development of the disease, its duration and degree. A portable recorder is connected to the patient, which reads changes in the heart. Monitoring is carried out for a certain time – at least a day, a maximum of a week.
    • ChEFI (trans-food electrophysiological study) – the procedure is complex. A special impulse tube is inserted through the nasal opening or esophagus, which delivers a weak electric current, causing tachycardia attacks. This allows you to determine the feature and type of tachycardia.
    • Echocardiography examines changes in the valves, walls and septa.

    Therapy of reciprocal AV nodal tachycardia is aimed at neutralizing symptoms and restoring normal heart rhythm. First of all, antiarrhythmic therapy is prescribed. The selection of drugs is carried out exclusively by a cardiologist. These funds prevent a violation of the heartbeat.

    If tachycardia occurs in rare cases, then the drugs are taken once, that is, only during the attack period. In other cases, the cardiologist prescribes an individual dosage and duration of treatment.

    Reflex receptions are very popular: Valsalva’s test and massaging of carotid sinuses are carried out. Valsalva’s test is based on forced respiratory movements.

    Indications for the operation:

    • if there are persistent bouts of reciprocal tachycardia;
    • in the presence of labor activity, which poses a threat to the life of the patient during an attack;
    • if it is impossible to get rid of a tachycardic attack with the help of medications;
    • with poor tolerance of attacks;
    • young age, since taking many drugs can lead to infertility.

    To date, it is customary to use only one surgical method – catheter (radio frequency) ablation. This technique is relatively innovative and safe.

    Refers to a minimally invasive method of surgery. During the procedure, a catheter electrode is inserted through a large aorta, which destroys the unnecessary path through radio-frequency radiation.

    The operation practically does not cause complications.

    At home, experts recommend physiotherapeutic procedures:

    • you can relieve the attack by washing with cold water;
    • it is useful to make cool douches and a contrast shower;
    • the bath can be filled with medicinal herbs;
    • it is important after a shower to thoroughly rub the body with a towel;
    • if possible, attend hydromassage procedures.

    Recipes of folk remedies for oral administration:

    • Buy the root part of the lovage from the pharmacy. Separate 20 grams and pour 0,5 liters of boiling water, but not cool. It is advisable to place the tincture in a thermos for 6-8 hours. After filtering, you can use it in small portions throughout the day.
    • Fresh viburnum helps to normalize the tachycardic heartbeat. Place a glass of berries in a jar, fill with boiling water (650-700 ml is enough), cover tightly with a lid. Put the container in a warm place for 6-7 hours. Now strain the tincture and squeeze the juice from the berries. Add 150-180 ml of natural honey to the total mass. Take the drug three times a day before meals, 70-80 ml. The duration of treatment is 30 days, after which you need to take a ten-day break.
    • Helps to cope with the attack of a regular broth of rose hips. If you take it constantly, you will saturate the body with useful substances, which will strengthen the immune system.
    • You can brew hawthorn in the standard way or buy a ready-made tincture in a pharmacy.

    This disease is not dangerous to health, but ignoring this pathology can lead to heart failure.

    To maintain normal condition, you must:

    • refuse to drink alcohol and tobacco;
    • follow a diet – eat more fresh vitamins, natural minerals and trace elements;
    • refuse bad cholesterol food;
    • timely diagnose diseases of the lungs and heart, as well as get rid of various pathologies;
    • avoid stressful situations and psychoemotional bursts;
    • move more and engage in permitted sports.

    Reciprocal tachycardia is a hereditary disease. Pathology does not pose a particular danger to human life, but it must be treated, since there is a risk of heart failure, which subsequently leads to death.

    Paroxysmal atrioventricular nodal reciprocal tachycardia (PAVURT) – suddenly starting and suddenly stopping tachycardia attacks that occur as a result of the functioning of re-entry in the AV node. Paroxysms can occur at any age.

    The morphological basis is the presence of several paths in the AV – node that have different electrophysiological properties: a – the path (channel) is slow, has a short effective refractory period (EP), located at the bottom and in the back of the AV – node; b – the path is fast, with a long ERP, located at and in front of the AV – node.

    Classification Typical (slow – fast, or slow – fast) PAVURT Atypical fast – slow (fast – slow) PAVURT.

    Causes

    Etiology. Congenital predisposition. The triggering factors for the development of paroxysms are psycho-emotional stress, physical activity, and alcohol intake.

    Pathogenesis Typical (slow – fast, or slow – fast) PAVURT – impulse enters the ventricles through the slow a – path, and returns to the atria along the fast b – channel Necessary conditions – a – the path is anterograd, b – the path is anterograde and retrograde, anterograde EPR b – channel larger than anterograde ERP of a – channel Atypical fast – slow PAVURT – impulse enters the ventricles along the fast b – path, and returns to the atria via the slow a – channel Necessary conditions – a – and b – paths function as in antero. and in the retrograde direction, the retrograde ERP of the b – channel is larger than the retrograde ERP of the a – channel.

    Symptoms (signs)

    Clinical manifestations – see supraventricular tachycardia.

    Diagnostics

    Diagnosis Standard ECG Transesophageal ECG Transesophageal and intracardiac electrophysiological examination.

    ECG – identification Typical (slow – fast, or slow – fast) PAVURT begins after the atrial extrasystole, less often – after the ventricular P – Q interval of the atrial extrasystole significantly lengthens The regular tachycardia rhythm, heart rate 140–240 per minute, mainly 160–220 per minute Complexes QRS is narrow, P wave, negative in leads II, III, aVF and positive in leads I, aVL, V5-6.

    associated with QRS, overlays with QRS or located behind QRS, R – P interval less than 100 ms, R – P less than 1/2 R – R Possible development of AV – blockade without cessation of tachycardia Atypical fast – slow (fast – slow) PAVURT begins after ventricular aestrasystole Regular rhythm, heart rate 140–240 per minute. QRS complexes are narrow, P wave is negative in leads II, III and aVF, positive in leads I, aVL, V5–6. associated with QRS, located far beyond QRS, the R – P interval is greater than 100 ms, R – P is greater than 1/2 R – R AV blockade may develop without cessation of tachycardia.

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    Tatyana Jakowenko

    Editor-in-chief of the Detonic online magazine, cardiologist Yakovenko-Plahotnaya Tatyana. Author of more than 950 scientific articles, including in foreign medical journals. He has been working as a cardiologist in a clinical hospital for over 12 years. He owns modern methods of diagnosis and treatment of cardiovascular diseases and implements them in his professional activities. For example, it uses methods of resuscitation of the heart, decoding of ECG, functional tests, cyclic ergometry and knows echocardiography very well.

    For 10 years, she has been an active participant in numerous medical symposia and workshops for doctors - families, therapists and cardiologists. He has many publications on a healthy lifestyle, diagnosis and treatment of heart and vascular diseases.

    He regularly monitors new publications of European and American cardiology journals, writes scientific articles, prepares reports at scientific conferences and participates in European cardiology congresses.

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