Transient sinoatrial block. Features of diagnosis and treatment of sinoatrial heart block. Brachial plexus block

RCHR (Republican Center for Health Development of the Ministry of Health of the Republic of Kazakhstan)
Version: Clinical protocols of the Ministry of Health of the Republic of Kazakhstan - 2014

Bifascicular block (I45.2), Other and unspecified atrioventricular block (I44.3), Second degree atrioventricular block (I44.1), First degree atrioventricular block (I44.0), Complete atrioventricular block (I44.2), Sick sinus syndrome (I49.5), Trifascicular block (I45.3)

Cardiology

general information

Short description

Approved
at the Expert Commission on Healthcare Development
Ministry of Health of the Republic of Kazakhstan
Protocol No. 10 dated July 04, 2014

AV block represents a slowdown or cessation of impulses from the atria to the ventricles. For the development of AV block, the level of damage to the conduction system may vary. This may be a conduction disorder in the atria, AV junction, and ventricles.

I. INTRODUCTORY PART

Protocol name: Cardiac conduction disorders

Protocol code

ICD-10 codes:
I44.0 First degree atrioventricular block
I44.1 Second degree atrioventricular block
I44.2 Complete atrioventricular block
I44.3 Other and unspecified atrioventricular block
I45.2 Double bundle block
I45.2 Trifascicular block
I49.5 Sick sinus syndrome

Abbreviations used in the protocol:
HRS - Heart Rhythm Society
NYHA - New York Heart Association
AV block - atrioventricular block
blood pressure - arterial pressure
ACE - angiotensin-converting enzyme
VVFSU - sinus node function recovery time
HIV - human immunodeficiency virus
VSAP - sinoauricular conduction time
ACE inhibitors - angiotensin-converting enzyme inhibitors
IHD - ischemic disease hearts
HV interval - impulse conduction time according to the His-Purkinje system
ELISA - linked immunosorbent assay
LV - left ventricle
MPCS - maximum duration of the stimulation cycle
SVC - sinus cycle duration
PCS - duration of the stimulation cycle
SA block - sinoatrial block
HF - heart failure
SNA - sinoatrial node
FGDS - fibrogastroduodenoscopy
HR - heart rate
ECG - electrocardiogram
EX - pacemaker
ERP - effective refractory period
EPI - electrophysiological study
EchoCG - echocardiography
EEG - electroencephalography

Date of development of the protocol: year 2014

Protocol users: interventional arrhythmologists, cardiologists, therapists, doctors general practice, cardiac surgeons, pediatricians, emergency doctors, paramedics.

Classification

Classification of AV block by degree:

First degree AV block is characterized by a slowdown in the conduction of impulses from the atria to the ventricles. The ECG shows a prolongation P-Q interval more than 0.18-0.2 sec.

. With second degree AV block, single impulses from the atria sometimes do not pass into the ventricles. If this phenomenon occurs rarely and only one ventricular complex is lost, patients may not feel anything, but sometimes they feel moments of cardiac arrest, during which dizziness or darkening occurs in the eyes.

AV block of the second degree, type Mobitz I - the ECG shows a periodic prolongation of the P-Q interval followed by a single P wave, which does not have a subsequent ventricular complex (type I block with Wenckebach periodicity). Typically, this variant of AV block occurs at the level of the AV junction.

AV block of the second degree, type Mobitz II, is manifested by periodic loss of QRS complexes without a previous prolongation of the PQ interval. The block level is usually the His-Purkinje system, the QRS complexes are wide.

. Third degree AV block (complete atrioventricular block, complete transverse block) occurs when electrical impulses from the atria are not conducted to the ventricles. In this case, the atria contract at a normal rate, and the ventricles contract rarely. The frequency of ventricular contractions depends on the level at which the center of automaticity is located.

Sick sinus syndrome
SSS is a dysfunction of the sinus node, manifested by bradycardia and accompanying arrhythmias.
Sinus bradycardia - a decrease in heart rate less than 20% below the age limit, migration of the pacemaker.
SA block is a slowdown (below 40 beats per minute) or cessation of impulse transmission from the sinus node through the sinoatrial junction.

Classification of SA block by degree :

The first degree of SA block does not cause any changes in cardiac activity and does not appear on a regular ECG. With this type of blockade, all sinus impulses pass to the atria.

With second-degree SA block, sinus impulses sometimes do not pass through the SA junction. This is accompanied by loss of one or more atrioventricular complexes in a row. With a second degree block, dizziness, a feeling of irregular heart activity, or fainting may occur. During pauses of SA blockade, escape contractions or rhythms may appear from underlying sources (AV junction, Purkinje fibers).

With third-degree SA block, impulses from the SPU do not pass through the SA junction and cardiac activity will be associated with the activation of the following rhythm sources.

Tachycardia-bradycardia syndrome- combination of sinus bradycardia with supraventricular heterotopic tachycardia.

Sinus arrest is a sudden cessation of cardiac activity with the absence of contractions of the atria and ventricles due to the fact that the sinus node cannot generate an impulse for their contraction.

Chronotropic insufficiency(incompetence) - inadequate increase in heart rate in response to physical activity.

Clinical classification AV blocks

According to the degree of AV block:
. 1st degree AV block

AV block II degree
- Mobitz type I

Type Mobitz II
- AV block 2:1
- High degree AV block - 3:1, 4:1

AV block III degree

Fascicular block
- Bifascicular blockade
- Trifascicular block

By time of occurrence:
. Congenital AV block
. Acquired AV block

According to the stability of AV block:
. Permanent AV block
. Transient AV block

Sinus node dysfunction:
. Sinus bradycardia
. Sinus arrest
. SA blockade
. Tachycardia-bradycardia syndrome
. Chronotropic insufficiency

Diagnostics

II. METHODS, APPROACHES AND PROCEDURES FOR DIAGNOSIS AND TREATMENT

List of basic and additional diagnostic measures

Basic (mandatory) diagnostic examinations performed on an outpatient basis:
. ECG;
. Holter ECG monitoring;
. Echocardiography.

Additional diagnostic examinations performed on an outpatient basis:
If organic cerebral pathology is suspected or in case of syncope of unknown origin:

X-ray of the skull and cervical spine spine;

. EEG;
. 12/24-hour EEG (if epileptic genesis of paroxysms is suspected);

. Doppler ultrasound (if pathology of extra- and intracranial vessels is suspected);

General blood test (6 parameters)

General urine analysis;

. coagulogram;
. HIV ELISA;

. FGDS;

The minimum list of examinations that must be carried out when referring for planned hospitalization:
. general analysis blood (6 parameters);
. general urine analysis;
. microprecipitation reaction with antilipid antigen;
. biochemical analysis blood (ALAT, AST, total protein, bilirubin, creatinine, urea, glucose);
. coagulogram;
. HIV ELISA;
. ELISA for markers viral hepatitis B, C;
. blood type, Rh factor;
. general radiography of organs chest;
. FGDS;
. additional consultations with relevant specialists if available concomitant pathology(endocrinologist, pulmonologist);
. consultation with a dentist or otolaryngologist to exclude foci of chronic infection.

Basic (mandatory) diagnostic examinations carried out at the hospital level:
. ECG;
. Holter ECG monitoring;
. Echocardiography.

Additional diagnostic examinations carried out at the hospital level:
. carotid sinus massage;
. sample with physical activity;
. pharmacological tests with isoproterenol, propronolol, atropine;
. EPI (performed in patients with clinical symptoms in whom the cause of symptoms is unclear; in patients with asymptomatic His bundle branch block, if pharmacotherapy is planned that can cause AV block);

If organic cerebral pathology is suspected or in case of syncope of unknown origin:
. radiography of the skull and cervical spine;
. examination of the fundus and visual fields;
. EEG;
. 12/24 - hourly EEG (if epileptic genesis of paroxysms is suspected);
. echoencephaloscopy (if there is a suspicion of space-occupying processes in the brain and intracranial hypertension);
. CT scan(if there is a suspicion of space-occupying brain processes and intracranial hypertension);
. Doppler ultrasound (if pathology of extra- and intracranial vessels is suspected);

Diagnostic measures carried out at the emergency stage emergency care :
. blood pressure measurement;
. ECG.

Diagnostic criteria

Complaints and anamnesis- main symptoms
. Loss of consciousness
. Dizziness
. Headache
. General weakness
. Determine the presence of diseases predisposing to the development of AV block

Physical examination
. Pallor skin
. Sweating
. Rare pulse
. Auscultation - bradycardia, first heart sound of varying intensity, systolic murmur above the sternum or between the apex of the heart and the left edge of the sternum
. Hypotension

Laboratory tests: not carried out.

Instrumental studies
ECG and daily ECG monitoring (main criteria):

With AV block:
. Rhythm pauses of more than 2.5 seconds ( R-R interval)
. Signs of AV dissociation (lack of conduction of all P waves to the ventricles, which leads to complete dissociation between P waves and QRS complexes)

With SSSU:
. Rhythm pauses of more than 2.5 seconds (P-P interval)
. Increase in the P-P interval by 2 or more times the normal P-P interval
. Sinus bradycardia
. No increase in heart rate during emotional/physical stress (chronotropic insufficiency of the heart rate)

EchoCG:
. Hypokinesis, akinesis, dyskinesis of the walls of the left ventricle
. Changes in the anatomy of the walls and cavities of the heart, their relationship, the structure of the valve apparatus, systolic and diastolic function of the left ventricle

EFI (additional criteria):

. With SSSU:

	Test	Normal answer	Pathological response
1	VVFSU	<1,3 ПСЦ+101мс	>1.3 PSC+101ms
2	Corrected VVFSU	<550мс	>550ms
3	MPCS	<600мс	>600ms
4	VSAP (indirect method)	60-125ms	>125ms
5	Direct method	87+12ms	135+30ms
6	Electrogram SU	75-99ms	105-165ms
7	ERP SPU	325+39ms (PCS 600ms)	522+39ms (PCS 600ms)

With AV block:

Prolongation of the HV interval more than 100 ms

Indications for consultation with specialists (if necessary, according to the decision of the attending physician):

Dentist - sanitation of foci of infection

Otolaryngologist - to exclude foci of infection

Gynecologist - to exclude pregnancy, foci of infection

Differential diagnosis

Differential diagnosis cardiac conduction disorders: SA and AV blockade

Differential diagnosis with AV blockade
SA blockade	Analysis of the ECG in a lead in which the P waves are clearly visible allows us to detect during pauses the loss of only the QRS complex, which is typical for AV block of the second degree, or simultaneously this complex and the P wave, characteristic of SA block of the 2nd degree
Escaping rhythm from the AV junction	Availability on ECG waves P, following regardless of the QRS complexes with a higher frequency, distinguishes complete AV block from an escape rhythm from the atrioventricular junction or idioventricular when the sinus node stops
Blocked atrial extrasystole	In favor of blocked atrial or nodal extrasystoles, in contrast to second degree AV block, is evidenced by the absence of a pattern of loss of the QRS complex, a shortening of the P-P interval before the loss compared to the previous one, and a change in the shape of the P wave, after which the ventricular complex falls out, compared to preceding P waves sinus rhythm
Atrioventricular dissociation	Required condition development of atrioventricular dissociation and main criterion its diagnosis is a high frequency of the ventricular rhythm compared to the frequency of atrial excitation caused by the sinus or ectopic atrial pacemaker.

Differential diagnosis for SSSU
	Test	Normal answer	Pathological response
1	Carotid sinus massage	Decreased sinus rhythm (pause< 2.5сек)	Sinus pause>2.5 sec
2	Exercise test	Sinus rhythm ≥130 at stage 1 of the Bruce protocol	There are no changes in sinus rhythm or the pause is insignificant
3	Pharmacological tests
A	Atropine (0.04 mg/kg, i.v.)	Increased sinus rate ≥50% or >90 beats/min	Increased sinus rhythm<50% или<90 в 1 минуту
b	Propranolol (0.05-0.1 mg/kg)	Decreased sinus rhythm<20%	The decrease in sinus rhythm is more significant
V	Own heart rate (118.1-0.57* age)	Own heart rate within 15% of calculated	<15% от расчетного

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Treatment

Treatment goals:

Improving life prognosis (preventing sudden cardiac death, increasing life expectancy);

Improving the patient's quality of life.

Treatment tactics

Non-drug treatment:

Bed rest;

Diet No. 10.

Drug treatment

with acute development of AV block, SSSU before pacemaker installation(mandatory, 100% probability)

Drug treatment provided on an outpatient basis before hospitalization:

List of essential medicines(having a 100% probability of application).

List of additional medicines(less than 100% chance of application)

№	Additional	Quantity per day	Duration of use	Likelihood of application
1	0.5% dopamine solution 5 ml	1-2	1-2	50%
2		1	1-2	50%
3	1% phenylephrine solution 1 ml	1-2	1-2	50%

Drug treatment provided at the inpatient level

List of essential medicines(having a 100% probability of application)

List of additional medicines c (less than 100% probability of application).

№	Additional	Quantity per day	Duration of use	Likelihood of application
1	0.5% dopamine solution 5 ml	1-2	1-2	50%
2	0.18% epinephrine solution 1 ml	1	1-2	50%
3	1% phenylephrine solution 1 ml	1-2	1-2	50%

Drug treatment provided at the emergency stage

№	Basic	Quantity per day	Duration of use	Likelihood of application
1	0.1% atropine sulfate solution 1 ml	1-2	1-2	100%
2	0.18% epinephrine solution 1 ml	1	1-2	50%
3	1% phenylephrine solution 1 ml	1-2	1-2	50%

Other treatments:(at all levels of medical care)

For hemodynamically significant bradycardia:

Place the patient with the lower limbs elevated at an angle of 20° (if there is no pronounced congestion in the lungs);

Oxygen therapy;

If necessary (depending on the patient’s condition), closed heart massage or rhythmic tapping on the sternum (“fist rhythm”);

It is necessary to discontinue drugs that could cause or worsen AV block (beta-blockers, slow calcium channel blockers, antiarrhythmic drugs of classes I and III, digoxin).

These measures are carried out until the patient’s hemodynamics are stabilized.

Surgical intervention

Electrocardiostimulation- the main method of treating cardiac conduction disorders. Bradyarrhythmias account for 20-30% of all heart rhythm disorders. Critical bradycardia threatens the development of asystole and is a risk factor for sudden death. Severe bradycardia worsens the quality of life of patients, leading to dizziness and syncope. Elimination and prevention of bradyarrhythmias will solve the problem of threat to life and disability of patients. ECS are implantable automatic devices designed to prevent bradycardic episodes. The electrical stimulation system includes the device itself and electrodes. According to the number of electrodes used, pacemakers are divided into single-chamber and double-chamber.

Surgical intervention provided on an outpatient basis: no.

Surgical intervention provided in a hospital setting

Indications for permanent pacing in AV block

Class I

Third degree AV block and progressive second degree AV block of any anatomical level associated with symptomatic bradycardia (including heart failure) and ventricular arrhythmias due to AV block (Level of Evidence: C)

Third degree AV block and progressive second degree AV block of any anatomical level associated with arrhythmias and other medical conditions requiring medical treatment causing symptomatic bradycardia (Level of Evidence: C)

Third degree AV block and progressive second degree AV block at any anatomical level with documented periods of asystole greater than or equal to 2.5 seconds, or any escape rhythm<40 ударов в минуту, либо выскальзывающий ритм ниже уровня АВ узла в бодрствующем состоянии у бессимптомных пациентов с синусовым ритмом (Уровень доказанности: С)

Third degree AV block and progressive second degree AV block of any anatomical level in asymptomatic patients with AF and documented at least one (or more) pause of 5 seconds or more (Level of Evidence: C)

Third degree AV block and progressive second degree AV block of any anatomical level in patients after catheter ablation of the AV node or His bundle (Level of Evidence: C)

Third degree AV block and progressive second degree AV block of any anatomical level in patients with postoperative AV block if its resolution is not predicted after cardiac surgery (Level of Evidence: C)

Third degree AV block and progressive second degree AV block of any anatomical level in patients with neuromuscular diseases with AV block, such as myotonic muscular dystrophy, Kearns-Sayre syndrome, Leiden dystrophy, peroneal muscular atrophy, with or without symptoms (Level of Evidence: B )

Third degree AV block, regardless of the type and location of block, with associated symptomatic bradycardia (Level of Evidence: B)

Persistent third-degree AV block of any anatomical level with an escape rhythm of less than 40 beats per minute while awake - in patients with cardiomegaly, LV dysfunction, or an escape rhythm below the level of the AV node who do not have clinical manifestations of bradycardia (Level of Evidence: B)

AV block II or III degree, occurring during an exercise test in the absence of signs of coronary artery disease (Level of evidence: C)

Class IIa

Asymptomatic persistent third-degree AV block at any anatomic site, with a mean awake ventricular rate >40 beats per minute, especially with cardiomegaly or left ventricular dysfunction (Level of Evidence: B, C)

Asymptomatic AV block of the second degree, type II at the intra- or infragisial level, detected by EPI (Level of evidence: B)

Asymptomatic second degree AV block type II with narrow QRS. If asymptomatic second-degree AV block occurs with a widened QRS, including isolated RBBB, the indication for pacing moves to a Class I recommendation (see next section on chronic bifascicular and trifascicular block) (Level of Evidence: B)

AV block I or II degree with hemodynamic disturbances (Level of evidence: B)

Class IIb

Neuromuscular diseases: myotonic muscular dystonia, Kearns-Sayre syndrome, Leiden dystrophy, peroneal muscular atrophy with AV block of any degree (including AV block of the first degree), with or without symptoms, because there may be unpredictable disease progression and deterioration of AV conduction (Level of Evidence: B)

When AV block occurs due to the use of drugs and/or their toxic effects, when resolution of the block is not expected, even if the drug is discontinued (Level of Evidence: B)

First-degree AV block with a PR interval greater than 0.30 sec in patients with left ventricular dysfunction and congestive heart failure in whom a shorter A-V interval results in hemodynamic improvement, presumably by reducing left atrial pressure (Level of Evidence: C)

Class IIa

The absence of a visible connection between syncope and AV block when excluding their connection with

Ventricular tachycardia (Level of evidence: B))

Incidental detection during invasive EPS of an apparently prolonged HV interval >100 ms in asymptomatic patients (Level of Evidence: B)

Detection during invasive electrophysiological study of non-physiological AV block below the His bundle, developing during stimulation (Level of evidence: B)

Class IIc

Neuromuscular diseases such as myotonic muscular dystonia, Kearns-Sayre syndrome, Leiden dystrophy, peroneal muscular atrophy with fascicular block of any degree, with or without symptoms, because there may be an unpredictable increase in atrioventricular conduction disturbances (Level of Evidence: C)

Indications for planned hospitalization:

AV block II-III degree

Indications for emergency hospitalization:

Syncope, dizziness, hemodynamic instability (systolic blood pressure less than 80 mmHg).

Information

Sources and literature

Minutes of meetings of the Expert Commission on Health Development of the Ministry of Health of the Republic of Kazakhstan, 2014
1. 1. Brignole M, Auricchio A. et al. 2013 ESC The Task Force on cardiac pacing and resynchronization therapy of the European Society of Cardiology (ESC). Developed in collaboration with the European Heart Rhythm Association (EHRA). Guidelines on cardiac pacing and cardiac resynchronization therapy. European Heart Journal (2013) 34, 2281–2329. 2. Brignole M, Alboni P, Benditt DG, Bergfeldt L, Blanc JJ, Bloch Thomsen PE, van Dijk JG, Fitzpatrick A, Hohnloser S, Janousek J, Kapoor W, Kenny RA, Kulakowski P, Masotti G, Moya A, Raviele A, Sutton R, Theodorakis G, Ungar A, Wieling W; Task Force on Syncope, European Society of Cardiology. Guidelines on management (diagnosis and treatment) of syncope-update 2004. Europace 2004;6:467 – 537 3. Epstein A., DiMarco J., Ellenbogen K. et al. ACC/AHA/HRS 2008 guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: a Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation 2008;117:2820-2840. 4. Fraser JD, Gillis AM, Irwin ME, Nishimura S, Tyers GF, Philippon F. Guidelines for pacemaker follow-up in Canada: a consensus statement of the Canadian Working Group on Cardiac Pacing. Can J Cardiol 2000;16:355-76 5. Gregoratos G, Abrams J, Epstein AE, et al. ACC/AHA/NASPE 2002 17 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices-summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/NASPE Committee to Update the 1998 Pacemaker Guidelines). J Am Coll Cardiol. 40: 2002; 1703–19 6. Lamas GA, Lee K, Sweeney M, et al. The mode selection trial (MOST) in sinus node dysfunction: design, rationale, and baseline characteristics of the first 1000 patients. Am Heart J. 140: 2000; 541–51 7. Moya A., Sutton R., Ammirati F., Blanc J.-J., Brignole M., Dahm, J.B., Deharo J-C, Gajek J., Gjesdal K., Krahn A., Massin M., Pepi M., Pezawas T., Granell R.R., Sarasin F., Ungar A., J. Gert van Dijk, Walma E.P. Wieling W.; Guidelines for the diagnosis and management of syncope (version 2009). Europace 2009. doi:10.1093/eurheartj/ehp29 8. Vardas P., Auricchio A. et al. Guidelines for cardiac pacing and cardiac recynchronization therapy. The Task Force for Cardiac Pacing and Cardiac Recynchronization Therapy of the European Society of Cardiology. Developed in Collaboration with the European Heart Rhythm Association. European Heart Journal (2007) 28, 2256-2295 9. Zipes DP, Camm AJ, Borggrefe M, et al. ACC/AHA/ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death). J Am Coll Cardiol. 48: 2006; e247–e346 10. Bockeria L.A., Revishvili A.Sh. et al. Clinical recommendations for electrophysiological studies and catheter ablation and for the use of implantable antiarrhythmic devices. Moscow, 2013
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All human organs and systems are interconnected. Violation of the functions of one organ immediately affects others. However, there are organs that, even if they stop working, do not pose a real threat to human health and life, since their functions are taken over by others. And there are those that, at the slightest disruption, significantly disrupt human life.

The heart is an irreplaceable organ. Moreover, any violation of its functions affects every cell of the body. Many diseases can disrupt its activity. One of them is sinoatrial block, also called sinoauricular or SA block. What do these concepts mean, what danger does this disease pose, what causes contribute to its development, and can it be cured?

general description

To understand what sinoatrial A-blockade is, you need to understand the anatomical features of the heart muscle. As you know, the heart is a pumping mechanism that pumps blood through the contraction of the heart chambers - the atria and ventricles. At the same time, the contractions themselves become possible thanks to electrical impulses formed in the sinoatrial or sinus node.

This component of the heart is one of the pacemakers, which is located in the right atrium. And it consists of several branches, which include the Thorel, Bachmann and Wenckebach bundle. These branches carry electrical impulses to both atria. Sinoatrial block is a condition in which the conduction of impulses is disrupted.

Sinoatrial block, as a rule, occurs against the background of other cardiac pathologies, as a result of which scars and other obstacles are formed in the heart muscle, interfering with the conduction of the impulse. As a result, a person develops arrhythmia, which leads to asystole. Asystole is a dangerous condition in which the heart stops as a result of the disappearance of electrical activity.

It should be noted that sinoatrial blockade accounts for no more than 0.16% of all heart diseases. That is, the disease is quite rare, and it is most often diagnosed in men who have crossed the 50-year mark.

However, SA blockade is also diagnosed in children. However, in childhood, disturbances in the conduction of electrical impulses are usually caused by congenital heart diseases.

Reasons for the development of SA blockade

Among the main causes of impulse conduction disturbances, the following can be noted:

damage to the sinus node;
violation of impulse propagation throughout the myocardium;
change in the tone of the vagus nerve.

In some cases, the disease occurs because the impulse is not formed at all, or it is so weak that myocardial cells, called cardiomyocytes, are unable to recognize it, or they are insensitive to it. It is not uncommon for an impulse to encounter obstacles in the form of scars through which it cannot pass.

There are many factors that can provoke the development of sinoatrial block. These include the following pathologies:

heart defects, both congenital and acquired;
inflammatory processes in the myocardium;
systemic connective tissue diseases;
damage to heart tissue due to cancer or injury;
coronary heart disease, developing against the background of cardiosclerosis, or as a consequence of myocardial infarction;
myocardial infarction, which causes death of a section of the heart muscle;
cardiomyopathy;
some types of VSD;
intoxication of the body caused by an overdose of certain medications or intolerance to them, as well as poisoning by various chemicals.

The functions of the sinus node are directly influenced by the vagus nerve. Sinoatrial blockade can occur when its activity changes. However, in this case, as a rule, it does not pose a serious threat to human life, since it can pass without medical intervention.

Types of SA blockade and symptoms

Based on the severity of the arrhythmia, sinoatrial blockade is divided into several degrees:

1st degree;
2nd degree;
3rd degree.

SA blockade 1st degree

In this case, we speak of incomplete SA blockade, when the sinus node functions uninterruptedly, and the impulses cause myocardial contractions in the atria. However, with this pathology, the heart muscle receives impulses somewhat less frequently than necessary. In this case, sick people do not feel any manifestations of the disease, and no changes are recorded during an ECG.

The presence of 1st degree SA blockade can be suspected based on a single sign – bradycardia. And it can only be diagnosed with an electrophysiological study of the heart.

SA blockade 2nd degree

A distinctive feature of 2nd degree sinoatrial block is that the formation of impulses does not always occur. As a result, in some cases there are no myocardial contractions, which is recorded on the ECG.

This pathology is divided into two types:

SA blockade of the second degree, type 1;
SA blockade of the second degree, type 2.

In the first case, impulse conduction decreases gradually. In this case, the patient is concerned about the following symptoms:

dizziness;
general weakness;
pre-fainting states;
short-term loss of consciousness.

Loss of consciousness can be provoked by any physical activity, as well as by turning the head or coughing.

In the second case, a persistent disturbance in heart rhythm occurs, accompanied by pauses, during which sick people feel weak and often lose consciousness.

SA blockade 3rd degree

This pathology poses the greatest danger, since the flow of impulses from the sinus node stops, which means that myocardial contraction does not occur. Sinoatrial block of the 3rd degree is very often accompanied by loss of consciousness, requiring resuscitation measures.

Signs of SA blockade in children

In children, pathology can be suspected based on signs similar to those in adults. Most often, the reason for contacting a doctor is the child’s rapid fatigue and fainting, accompanied by a blue discoloration of the nasolabial triangle.

Sinoauricular block on ECG

Electrocardiography of the heart is the main method to help diagnose disturbances in the conduction of electrical impulses. However, its implementation is not effective in the case of 1st degree sinoauricular block. The only signs of pathology in this case are bradycardia, to which the person adapts, and a shortening of the PQ interval.

With 2 degrees of pathology, the following deviations are recorded on the ECG:

the P-P indicator decreases, indicating a lengthening of the interval between atrial contractions;
after pauses there is a gradual reduction in the time of the P-P indicator;
one of the next PQRST complexes may be absent;
during pauses, impulses come from other pacemakers;
if several contractions occur, the duration of the pause is several P-P indicators.

With stage 3 pathology, an isoline is recorded on the ECG, indicating the absence of electrical impulses and myocardial contractions. During this period, the likelihood of death increases many times over.

Diagnosis of the disease

The main methods for diagnosing electrical conduction disorders of the heart are the following studies:

Holter ECG.

Holter ECG is effective if traditional electrocardiographic examination of the heart did not detect any changes. Holter monitoring is carried out for 3 days, which makes it possible to reliably assess disturbances in the functioning of the sinus node. This type of study is also indicated for children.

Another diagnostic method is the atropine test. We can talk about the presence of pathology if, after administering this substance, the patient’s pulse first increases and then sharply decreases, which will be indirect evidence of a blockade.

Ultrasound examination of the heart helps to find the cause of the malfunction of the sinus node. This type of study allows you to detect defects, scars and other pathological changes in the structure of the myocardium.

Treatment of the disease

Sinoatrial blockade of the 1st degree does not require special therapy. In most cases, treatment of the disease that caused its disturbance helps normalize the heart rhythm. If the malfunction of the sinus node was caused by taking any medications, they are canceled.

If the cause of the disease is a change in the activity of the vagus nerve, patients are prescribed drugs based on atropine. The same drugs are also prescribed to children with VSD that has caused myocardial conduction disturbances.

Nitroglycerin, Atropine, Platiphylline and Nidefilin help relieve severe attacks of arrhythmia. However, drug therapy in this case brings only temporary relief. In particularly severe cases, patients are advised to have a pacemaker installed.

All patients, regardless of the severity of the disease, are prescribed drugs that improve metabolic processes in the myocardium and its contractility.

In addition to taking medications, children are advised to reduce their loads, reduce the intensity of sports activities, and in some cases, refuse to attend child care facilities altogether. However, if the arrhythmia is transient and there is no risk to life, it is not recommended to isolate children. In this case, you just need to regularly visit your doctor and undergo the necessary tests.

SINOATRIAL (SA) BLOCK is characterized by a disturbance in the conduction of impulses from the sinus node to the atria.

THE ETIOLOGY of SA blockades largely coincides with the etiology of sick sinus syndrome (SSNS) and other sinus dysfunctions - these are degenerative calcifying lesions of intracardiac structures, numerous and varied myocardial pathologies, regulatory dysfunctions (excessive vagotonia), toxic (including drug) effects. SA blockade may be one of the manifestations of SSSS.

ECG DIAGNOSTICS. With SA block of the first degree, a slowdown in the conduction of impulses from the SA node to the atrial myocardium is observed. But an ECG study does not reveal this, because An external ECG does not record excitation of the sinus node, and the P wave is formed by depolarization of the atrial myocardium. Sinoatrial conduction time can only be assessed using special electrocardiographic methods. 1st degree SA block has no clinical manifestations.

SA block of the second degree (incomplete SA block) is characterized by blocking of one or more sinus impulses in a row. This is manifested by the loss of one or more sinus cycles (P waves and rUD complexes). The pauses that occur can be multiples of 2, less often 3-4, of the main R-R intervals, but are often interrupted by passive slipping complexes or rhythms. In the clinical and electrocardiographic characteristics of second degree SA block, two main types are distinguished:

SA blockade of the second degree, type I (Wenckenbach period in the SA junction) is characterized by loss of the sinus complex, which is preceded by a consistent shortening of the P-P intervals (Fig. 47). With this option, there is a progressive increase from cycle to cycle in the time of impulse conduction from the sinus node to the atrial myocardium, ending with complete blocking of the next impulse. At this moment, a pause is recorded, including a blocked impulse. The increase in conduction time in this periodical is maximum in its first cycles after a pause. Although in the future the conduction progressively worsens, the increase in this time (increment) decreases from complex to complex. In this regard, the ECG reveals a gradual shortening of the P-P intervals and after the shortest interval a pause occurs as a result of blocking one impulse in the SA junction. This pause is shorter than twice the P-R interval preceding the pause. Classical periodicals of Wenkenbach are less common than atypical periodicals with disordered fluctuations of P-P intervals or their progressive lengthening with blocking of the next sinus impulse. With repeated Wenckenbach periods, regular ratios are established between the number of sinus impulses and P waves - 3:2, 4:3, etc. At the moment the sinus impulse is blocked, the next P wave and QRS complex are absent on the ECG. Children at the time of loss of the cardiac cycle may feel a sinking heart, sometimes accompanied by dizziness. This variant of SA block is usually benign in nature.

Second degree SA block of type II (Mobitz block) is characterized by loss of the sinus complex without changes in the P-P intervals (Fig. 48). This type of block occurs in long pauses as a result of sudden blocking of one or more sinus impulses without preceding periodicity. Despite the absence of changes in the P-P intervals in the conducting complexes, a certain ratio can be established between the total number of sinus impulses and the number of impulses conducted to the atria - 2:1, 3:1, 3:2, 4:3, etc. Sometimes the loss can be sporadic. The extended P-P interval is equal to double or triple the main P-P interval. If the pause is prolonged, replacement complexes and rhythms arise. Regular 2:1 SA block mimics sinus bradycardia. If the cessation of conduction in the SA junction is prolonged to values of 4:1, 5:1 (the pause is a multiple of the duration of 4-5 normal cycles), they speak of advanced SA blockade of the second degree, type II. Frequent occurrence of long pauses is perceived as cardiac arrest and is accompanied by dizziness and loss of consciousness. The symptoms correspond to the manifestations of SSSU.

III degree SA block (complete SA block) is recognized using electrophysiological methods. The ECG shows a slow escape rhythm (most often the rhythm of the AV junction). Clinical symptoms may be absent or signs of regional (cerebral) hemodynamic disorders may appear with a rare replacement rhythm.

TREATMENT. The occurrence of SA blockade as a result of acute cardiac pathology requires active treatment of the underlying disease. In case of significant hemodynamic disturbances as a result of SA blockade, anticholinergics, sympathomimetics, and temporary cardiac pacing are used. With persistent SA blockade, the question of permanent cardiac pacing is raised.

General information

Sinoauricular (sinoatrial) block is a type of sick sinus syndrome in which the conduction of electrical impulses between the sinoatrial node and the atria is blocked. With sinoauricular block, temporary atrial asystole and loss of one or more ventricular complexes occur. Sinoauricular block is relatively rare in cardiology. According to statistics, this conduction disorder develops more often in men (65%) than in women (35%). Sinoauricular block can be detected at any age.

Causes of sinoauricular block

The development of sinoauricular block can be caused by damage to the sinus node itself, organic damage to the myocardium, and increased tone of the vagus nerve. Sinoauricular block occurs in patients with heart defects, myocarditis, ischemic heart disease (atherosclerotic cardiosclerosis, acute myocardial infarction, often posterior phrenic), cardiomyopathies. Sinoauricular block can develop as a result of intoxication with cardiac glycosides, potassium preparations, quinidine, adrenergic blockers, and poisoning with organophosphorus compounds.

Sometimes sinoatrial conduction disturbance occurs after defibrillation. In practically healthy individuals, sinoauricular block occurs when there is a reflex increase in the tone of the vagus nerve innervating the atrioventricular node and atrium. The mechanism of development of sinoauricular block may be directly related to the lack of impulse generation in the sinus node; weakness of the impulse, unable to cause atrial depolarization; blocking impulse transmission in the area between the sinus node and the right atrium.

Classification of sinoauricular block

There are sinoauricular blockades of I, II and III degrees. Sinoauricular block of the first degree is not detected on a regular electrocardiogram. In this case, all impulses generated by the sinus node reach the atria, but they originate less frequently than normal. Persistent sinus bradycardia may indirectly indicate sinoauricular block of the first degree.

With sinoauricular block of the second degree, some impulses do not reach the atria and ventricles, which is accompanied by the appearance of Samoilov-Wenckebach periods on the ECG - loss of the P wave and the associated QRST complex. In case of loss of one cardiac cycle, the increased R-R interval is equal to two main R-R intervals; if more cardiac cycles occur, the pause may be 3 R-R, 4 R-R. Sometimes the conduction of every second impulse following one normal contraction is blocked (sinoauricular block 2:1) - in this case they talk about allorhythmia.

Forecast and prevention of sinoauricular block

The development of events during sinoauricular block is largely determined by the course of the underlying disease, the degree of conduction disturbance, and the presence of other rhythm disturbances. Asymptomatic sinoauricular block does not cause severe hemodynamic disturbances; the development of Morgagni-Adams-Stokes syndrome is regarded as prognostically unfavorable.

Due to insufficient knowledge of the pathogenesis of sinoauricular blockade, its prevention has not been developed. The primary tasks in this direction are to eliminate the causes of conduction disturbances and monitor

Cardiologist

Higher education:

Cardiologist

Kuban State Medical University (KubSMU, KubSMA, KubGMI)

Level of education - Specialist

Additional education:

“Cardiology”, “Course on magnetic resonance imaging of the cardiovascular system”

Research Institute of Cardiology named after. A.L. Myasnikova

"Course on functional diagnostics"

NTsSSKh them. A. N. Bakuleva

"Course in Clinical Pharmacology"

Russian Medical Academy of Postgraduate Education

"Emergency Cardiology"

Cantonal Hospital of Geneva, Geneva (Switzerland)

"Therapy Course"

Russian State Medical Institute of Roszdrav

With transient 2nd degree AV block, the conduction of electrical impulses from the atria to the ventricles is partially disrupted. Atrioventricular block sometimes occurs without visible symptoms and may be accompanied by weakness, dizziness, angina, and in some cases loss of consciousness. The AV node is part of the conduction system of the heart, which ensures the sequential contraction of the atria and ventricles. When the AV node is damaged, the electrical impulse slows down or does not arrive at all and, as a result, a malfunction of the organ occurs.

Causes and extent of the disease

Second degree atrioventricular block can also be observed in healthy trained people. This condition develops during rest and goes away with physical activity. The most susceptible to this pathology are elderly people and people with organic heart disease:

ischemic disease;
myocardial infarction;
heart disease;
myocarditis;
heart tumor.

Sometimes the disease develops due to an overdose of drugs; congenital pathology is less common. The cause of atrioventricular block can be surgical interventions: insertion of a catheter into the right side of the heart, valve replacement, organ plastic surgery. Diseases of the endocrine system and infectious diseases contribute to the development of 2nd degree blockade.

In medicine, atrioventricular blocks are divided into 3 degrees. The clinical picture at stage 1 of the disease does not have pronounced symptoms. In this case, the passage of impulses in the organ area slows down.

Stage 2 is characterized by slowing down and partial passage of sinus impulses; as a result, the ventricles do not receive a signal and are not excited. Depending on the degree of loss of impulses, there are several options for 2nd degree blockade:

Mobitz 1 is characterized by a gradual lengthening of the P-Q interval, where the ratio of P waves and QRS complexes is 3:2, 4:3, 5:4, 6:5, etc.
Another variant, Mobitz 2, is characterized by incomplete blockade with a constant P-Q interval. After one or two pulses, the conductivity of the system deteriorates, and the third signal no longer arrives.
Option 3 implies a high degree of blockade 3:1, 2:1. During diagnosis, every second pulse that does not pass through is lost on the electrocardiogram. This condition leads the patient to a slow heart rate and bradycardia.

AV block (grade 2) with further deterioration leads to complete blockage, when not a single impulse passes to the ventricles. This condition is typical for stage 3 of the disease.

Symptoms and treatment

Symptoms of the pathology develop against the background of a rare heartbeat and circulatory disorders. Due to insufficient blood flow to the brain, dizziness occurs and the patient may lose consciousness for a while. The patient feels rare powerful tremors in the chest, and the pulse slows down.

When assessing the patient’s condition, the specialist finds out whether he has had previous heart attacks, cardiovascular diseases, and a list of medications taken. The main research method is electrocardiography, which allows you to capture and graphically reproduce the work of the cardiac system. Daily Holter monitoring allows you to assess the patient’s condition at rest and during light physical activity.

Additional studies are carried out using echocardiography, multispiral computed cardiography and magnetic resonance imaging.

If AV block (grade 2) occurs for the first time, the patient is prescribed a course of drug therapy. All medications that slow down impulse conduction are discontinued. Drugs are prescribed that increase the heart rate and block the influence of the nervous system on the sinus node. These drugs include: Atropine, Isadrine, Glucagon and Prednisolone. In cases of chronic disease, Belloid and Corinfar are additionally prescribed. Teopek is recommended for pregnant women and people suffering from epilepsy. The dosage is prescribed by the doctor depending on the patient’s condition.

Long-term heart failure contributes to the accumulation of fluid in the body. To eliminate congestion, take the diuretics Furosemide and Hydrochlorothiazide.

A severe form of the disease with 2nd degree AV block of the Mobitz type 2 requires radical treatment. For this purpose, an operation is performed to install a pacemaker - a device that controls the rhythm and frequency of the heart. Indications for surgery:

clinical picture of the patient’s condition with frequent fainting;
AV block (degree 2) Mobitz type 2;
Morgagni-Adams-Stokes attack;
heart rate less than 40 beats per minute;
heart failures with a frequency of more than 3 seconds.

Modern medicine uses the latest devices that work on demand: electrodes release pulses only when the heart rate begins to fall. The operation causes minimal damage and is performed under local anesthesia. After installing the stimulator, patients' pulse normalizes, pain disappears and their well-being improves. Patients must follow all doctor's instructions and visit a cardiologist. The operating life of the device is 7-10 years.

Forecast and prevention of the disease

In the chronic course of the pathology, serious complications are possible. Patients develop heart failure, kidney disease, arrhythmia and tachycardia, and there are cases of myocardial infarction. Poor blood supply to the brain leads to dizziness and fainting, and may impair intellectual activity. A Morgagni-Adams-Stokes attack becomes dangerous for a person, the symptoms of which are fever, pale skin, nausea and fainting. In such cases, the patient needs urgent help: cardiac massage, artificial respiration, calling intensive care. The attack can result in cardiac arrest and death.

Prevention of the disease consists of timely treatment of heart pathologies, hypertension, and control of blood sugar levels. It is necessary to avoid stress and overexertion.

In case of second degree AV block, the following is prohibited:

engage in professional sports;
be exposed to excessive physical exertion;
smoke and drink alcohol;
After installing a pacemaker, avoid electrical and electromagnetic fields, physiotherapeutic procedures and injuries to the chest area.

A routine electrocardiogram will help identify the disease in the early stages and carry out conservative treatment, which will contribute to the person’s full recovery and return to a normal lifestyle.