AV dissociation causes. Violation of conductivity

CHARACTERISTICS
Atrial and ventricular rhythms are generated independently from each other - caused by many mechanisms; Detected with many arrhythmias; It is not an electrocardiographic diagnosis.

THE REASONS
· Digoxin intoxication
· Myocarditis
· Cardiomyopathy
· Chronic valve failure
· Cognietal (congenital) heart disease
· Halloon anesthesia in cats

RISK FACTORS: The same as the causes

Pathophysiology
· Possible causes - a complete pathological interruption of the pulse between the atrium and the ventricle (complete av blockade), a temporary psychological break, and variable refractors in AV conduction.
· The combination of two or 3 of the following mechanisms cause AV dissociation:
· Reducing the automatism of the sinus node - allows the connecting AB or the ventricular center to slip out and monitor the ventricular independently;
· Enlarged automatism AV or Ventricular connection - In this case, the ectopic center controls the ventricle, and the sinus unit controls the atrium.
· An embarrassment in AV conducting a pulse - blockade AV assembly allows the action of two non-dependent rhythms, one in atrium and the other below the region of the impulse delay.
· Hemodynamic disorders caused by the reduced productivity of the heart can be detected by the deceleration of connecting and ventricular spelling rhythms or due to the presence of variable tachyrhythmia.

Affected systems: Cardiovascular

Susceptibility: Dogs and cats

CLINICAL SIGNS

Anamnese data
· Without clinical signs
· ZSN (HSN)
· Fast fatigue with physical. Load
· Sincop

General Clinical Research Data
· Pulsation of the yugular vein
· Regular or irregular rhythm
· Rhythm Galopa
· Clinical signs of stagnant heart failure

Differential diagnosis
· Atri or ventricular premature complexes
· Ventricular tachycardia
· Complete av blockade - atrial frequency faster than ventricular or in AV connections; AV (AV) dissociation atrial frequency is slow than the frequency in AV connections.

VISUALIZATION
Echocardiography and doppler ultrasound to determine the structures and functions of the heart.

ECG characteristics
· Sinus R waves do not have a permanent connection with QRS with accumsions.
· P Waves - can precede, be in the middle, or follow QRS complexes without changing them usually normal form.
· Frequency P waves - usually slower than the QRS frequency of the complex
· Ventricular exciting complex-sometimes P wave and QRS complex look like when conducting a pulse in the time of regular sinus rhythm; It is always manifested when the sinus or ectopic suprementaric pulse arrives when AV connecting and / or ventricular pathways are restored from the preceding pulse; this is called full av dissociation
· Ventricular mixed complexes sometimes appear as premature complexes during AV dissociation; P waves are always preceded; QRS The mixed reduction complex has a configuration similar to the one that is characteristic of a normal sinus complex for a ventricular ectopic complex; called incomplete AV (AV) dissociage.

Pathological changes: Variable-depends on the causes described.

TREATMENT
Principles of action
· Urgent or stationary - depends on the severity of clinical signs
· Treat the described stagnant heart failure or other reasons.
· Not an ECG is diagnosed; Description phenomenon is secondary, due to the different types of electrical abnormalities which require different treatment techniques (e.g., if the AV dissociation caused AV block, for this treatment may be pacemaker, if caused by the acceleration of the connecting rate, the animal may be reacted sharply on digoxin and has myocarditis )

Stationary care: Varies depending on the main reasons

PHYSICAL ACTIVITY: Limit if there is clinical symptoms.

Diets: We need only changes for the treatment of basic states (for example, diets with a decrease in sodium, for stagnant heart failure)

Informing customers: There may be necessary additional diagnostic studies to determine the causes and assign suitable therapy.

Surgical accounts
If AV dissociation is caused by av blockade, the treatment may be the implantation of a pacemaker.

Choice medicines
· Corrigate embarrassment in electrolyte and acid alkaline ballace.
· Credit the main disease of the heart is adequate.
· Look at the section where treatment is described for complete av blockade and for ventricular tachycardia.

Patient monitoring: Track cardiac frequency and rhythm through serial ECG.

Synonyms
· Full av dissociation
· Incomplete av dissociation

CM. ALSO
· Idiovativericular rhythm
· Atrioventricular blockade, full (third degree)
· Ventricular (ventricular) tachycardia

Abbreviation
AV \u003d Atrioventricular
ZSN \u003d chronic (stagnant) heart failure

• ECG (in II Deletion) with incomplete atrioventricular dissociation type of interference with dissociation. The frequency of impulsation from the heterotropic focus of automatism is higher, ...
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Discussion of ECG with incomplete atrioventricular dissociation type of interference with dissociation

• Av blockade of the II degree is quite serious pathology and it is associated with the lesion of the conductive heart system at the level (the conduction of the impulse from the atria to the ventricles) is violated). This pathology may be congenital (intrauterine infection, hereditary pathology) or acquired (most often Mio
• Negative Teeth T, if strictly by propapped, is a sign of subepicarudual ischemia. Judging by the leaders - in the side departments of myocardium left ventricle. BUT! Tusk T without other signs (pain and blood enzymes) is not specific. Those. Negative teeth of T can be: with violations

Atrioventricular dissociation and parasistolia

Atrioventricular dissociation is called the inconsistent activities of atrial and ventricles, not associated with a complete transverse blockade. At the same time, the atrium is reduced as a result of the pulses from the sinus unit, and the ventricles - pulses from the attir-tricular (AV) compound. The frequency of ectopic rhythm with dissociation is larger than sinus rhythm. The prerequisite for the development of AV dissociation is the presence of a normal orthograde and blocked retrograde conductivity. The atrial and ventricular rhythm is correct. The QRS complex has not been changed due to the orthograde propagation of the impulse. The pulses of the sinus node come to an atrioventricular node when it is in the refractory phase, and are blocked there. Normal teeth P are enjoyed on various sections of the QRS complex and the final part (Fig. 45).

If on the background of AV dissociation some of the sinus pulses reach ventricles and cause their excitement (i.e., captured abbreviations appear), then the correct rhythm av compound is violated by the reduction of ventricles under the influence of the pulse from the sinus node. In this case, before QRS, there is a normal P associated with the complex. Such a violation is called interfering dissociation or dissociation with interference (Fig. 46).

A special form of dissociation is an isoratemic disaction, in which the atrium and ventricles are activated by different sources of excitation (sinus unit and AV compound) in almost the same frequency (Fig. 47).

Under parasistoline understand the combination of two automatic centers. Parasistolic center is protected from the sinus rhythm of the blockade of the entrance. Parasistolia also has an output blockade that prevents the retrograde pulse to the sinus node. Parasystolic focus produces pulses with a certain frequency usually from the conductive ventricular system. The pharmaceutical fur of the pump of steamstolia is considered to be re-entry and the circulation of the trust. There are two rhythm driver on the ECG: a more frequent sinus node and a more rare ectopic rhythm. Parasistols follow

for each other at certain intervals, which are always painted in the smallest distance between parasistols (Fig. 48).

Parasistols can be inserted or accompanied by compensatory pauses as extrasystoles. Less often, parasistols come from atrias or from an atrioventricular node.

The diagnosis of parasistolia requires the removal of an ECG on a long tape in the second standard assignment.

Atrioventricular dissociation occurs when the atrium and ventricles have two different rhythm driver. In this case, the presence of a complete atrioventricular blockade may not be accompanied by a primary conduction disorder. An atrioventricular dissociation that is not associated with a blockade of the heart may occur under the following circumstances. First, with an atrioventricular nodal rhythm arising in response to heavy sinus bradycardia. If the sinus rhythm is similar to slipping rhythm, and teeth R arise immediately before the complex QRS Enjoy on it or follow him, they talk about the presence of an isa-nominal atrioventricular dissociation. In this case, it is necessary to eliminate the causes of sinus bradycardia, i.e., stop the reception of digitalis, B-blockers or calcium antagonists; accelerate the sinus rhythm by introducing vagolithic drugs; Install the electrocardialism if the rhythm of slipping is rare and is accompanied by the appearance of the corresponding symptoms. Secondly, atrioventricular dissociation may be caused by an increase in the activity of the subordinate, nodal or ventricular rhythm driver, which competes with a normal sinus rhythm and often even surpasses it. Such a situation obtained a name replacing an attainricular dissociation. In this case, the rapid rhythm of the underlying rhythm driver, acting retrograde to the atrial and ventricular node, bombards it, leading to a state of refractoriness in relation to normal sinus pulses. Such a violation of the antitegrand initiation is a physiological response to the circumstances, often arising during ventricular tachycardia, with intoxication by drugs, ischemia and / or myocardial infarction or local irritation of myocardium after the heart surgery. Accelerated rhythm should be corrected either by appointing antiarrhythmic drugs (see ch. 184), or by canceling the drug, which caused such a violation, or corrected metabolic disorders.

Using the data of intracardiac electrocardiography for the formulation of diagnosis and maintaining patients

The main question to which the doctor should respond, assigning treatment to the patient with an atrioventricular conductivity impaired, is the question of the need to establish an electrocardiotimulator. In a number of cases, its solution depends on the results of the registration of the electrocardiogram of the atreservant beam (Gis). There is no doubt that the provision that all patients with an atrioventricular blockade of II or III degree, accompanied by clinical symptoms of the disease, shows the electrostimulation of myocardium. In this regard, there is no need to resort to the electrophysiological study of such patients. Nevertheless, in the following cases, registration of intracardiac ECG is needed.

1. In persons susceptible to fainting and suffering blockade of the legs of the preservative beam (Gis), but not objective confirmations of the presence of an atrioventricular blockade. Obtaining such patients with a pronounced violation of the conductivity below the atreservant beam (Gis), i.e., the magnitude of the interval of the beam of Gis-myocardium ventricles is more than 80 ms, may indicate to establish an electrocardiotimulator. At the magnitude of this interval from 55 to 80 ms, the testimony for electrical stimulation is not absolute. Conducting electrophysiological research in this group of patients is most appropriate if the magnitude of the interval of the GIS is the myocardium of the ventricles remains within the normal range, less than 55 ms.

2. In patients with blockade of the branch of the atrocadic beam (Gis) and an atrioventricular blockade of the II degree. When they appear characteristic clinical symptoms of these disorders, the intracardiac registration of an electrocardiogram allows you to determine at what level [atrocaded-ventricular node, the atrief ventricular beam (Gis), below the Gis beam or on several levels at the same time] the blockade of the block shall be localized. On the localization of the lesion below the atrocadic beam (His) indicate the transient blockade of one of its legs in combination with a change in the size of the interval R-R. Intricultural studies performed in such cases indicate that if such patients have a conduction disorder, it is almost always localized in the Gis-Purkinier system. If the blockade is detected below the atrochematic beam (Gisa), accompanied by the asymptomatic flowing atrioventricular blockade of the II degree, such patients need to install an electrocardiality system, since they are great for the development of an atrioventricular blockade of a high degree and the appearance of clinical symptoms, including fainting.

Fig. 183-8. Atrioventricular blockade III degree.

There is a complete blockade of the heart with slow slip rhythm and wide complexes. In this case, it is usually localized in the atrial and ventricular beam (Gis). See text.

3. In patients with an atrioventricular blockade of the III degree flowing asymptomatic. In such a case, electrophysiological research helps to assess the stability of the nodal rhythm driver. It is shown to carry out electrostimulation in cases where the subordinate rhythm driver, which is at the level of the atrocadic beam (Gisa), cannot provide stable hemodynamics under exercise conditions, under the influence of atropyan or isoproterenol, as well as when the recovery time of the nodal pacemeter after stimulation Golders are very large.

4. In patients with blockade of the feet of a beam of Gis, in particular with a biphascicular blockade (see ch. 178). Registration of intraconductural ECGs, they make it possible to predict the risk of developing an atrioventricular blockade. The duration of the interval of GiSi - Miocardium of ventricles More than 80 ms does not yet indicate a mandatory development of the blockade at the level of the atrocarditricular beam (Gis). However, in patients in whom this figure is extremely increased and exceeds 100 ms, as well as in those with transient blockade legs atrioventricular bundle (His-) is accompanied by fluctuation range of values \u200b\u200bventriculonector - ventricular myocardium, complete atrioventricular block develops quite often. All this determines the need to establish an electrocardiotimulator. If the blockade is lower than the atreservant beam (Gisa), it develops at the atrial power stimulation with a frequency of less than 150 blows in 1 min, if the blockade is developing below the GISE beam or the interval of the GISE, the micard of ventricles increases to 100 ms and more after intravenous administration 1 g of Novocainamide, This indicates a high risk of an atrioventricular blockade and the need to establish an electrocardiotimulator.