Electrocardiography( ECG) - Causes, symptoms and treatment. MF.

As early as the 19th century, scientists, studying the anatomical and physiological features of the heart of animals and humans, came to the conclusion that this organ is a muscle capable of generating and conducting electrical impulses. The human heart consists of two auricles and two ventricles. Correct conduct of electrical signals on them causes good contractility of the myocardium( cardiac muscle) and provides the correct rhythm of contractions.

Initially, the impulse appears in the cells of the sinoatrial( atrial) node located on the right atrium and upper vena cava. Then it spreads to the atria, reaching the atrioventricular node( located between the right atrium and the ventricle), there is a small delay of the pulse, then passes through the bundle of the Gis in the thickness of the interventricular septum and spreads through the Purkinje fibers in the walls of both ventricles. It is this way of conducting an electrical signal through the conduction system of the heart that is right and provides a full-fledged cardiac contraction, because under the influence of the pulse, the muscle cell contracting.

Conducting heart system

A little later, scientists were able to create an apparatus that allows to record and read the processes of electrical activity in the heart by applying electrodes to the chest. A huge role here belongs to Willem Eithoven, a Dutch scientist who designed the first apparatus for electrocardiography and proved that in patients with various heart diseases the parameters of the electrophysiology of the heart change during the recording of the ECG( 1903).So, what is electrocardiography?

ECG is an instrumental method for studying the electrophysiological activity of the heart, based on the registration and graphic representation of the potential difference that occurs during the process of cardiac muscle contraction for the diagnosis of heart disease. The

ECG is performed by placing electrodes on the front wall of the chest in the projection of the heart and limb, then the cardiac electric potentials are recorded with the help of the ECG apparatus itself and displayed as a graphic curve on a computer monitor or thermal paper( using an ink recorder).The electrical impulses generated by the heart are spreading throughout the body, therefore, for the convenience of their reading, leads have been developed - circuits that allow the potential difference to be recorded in different parts of the heart. There are three standard leads - 1, 11, 111;three amplified leads - aVL, aVR, aVF;and six chest leads - from V1 to V6.All twelve leads are displayed on the ECG film and allow to see the work of this or that part of the heart in each specific lead.

In modern times, the electrocardiography method is very widespread due to its availability, ease of use, cheapness and lack of invasiveness( violation of the integrity of body tissues).ECG allows you to diagnose in time many diseases - acute coronary pathology( myocardial infarction), hypertension, rhythm and conduction disorders, etc., and also allows to evaluate the effectiveness of medical or surgical treatment of heart diseases.

The following methods of ECG are selected:

- Holter( daily) ECG monitoring - the patient is placed a portable small device on the chest, which records the slightest deviations in the activity of the heart during the day. The method is good because it allows you to observe the work of the heart with the usual daily activity of the patient and for a longer time than when removing a simple ECG.Helps in the recording of cardiac arrhythmias, myocardial ischemia, not detected with a single ECG.
- ECG with load - drug( using pharmacological drugs) or physical load( treadmill test, veloergometry);as well as electrical stimulation of the heart with the introduction of the sensor through the esophagus( PEPHI - perescheeschevodnoe electrophysiological study).It allows to diagnose the initial stages of IHD, when the patient complains of pain in the heart during physical activity, and the ECG does not detect changes at rest.
- transesophageal ECG - as a rule, is performed before PPEI, as well as in cases where the ECG through the anterior chest wall is of little informative and does not help the doctor determine the true nature of cardiac rhythm disturbances.

Indications for ECG

What is an ECG for? Electrocardiography makes it possible to diagnose many cardiac diseases. Indications for ECG are:

1. Routine examination of children, adolescents, pregnant women, military personnel, drivers, athletes, people over 40, patients before surgery, patients with other diseases( diabetes, thyroid, lung disease, digestive system diseasesand etc);

2. Diagnosis of diseases:
- arterial hypertension;
- ischemic heart disease( IHD), including acute, subacute myocardial infarction, postinfarction cardiosclerosis;
- endocrine, dysmetabolic, alcoholic toxic cardiomyopathies;
- chronic heart failure;
- heart diseases;
- rhythm and conduction disorders - CVS syndrome, atrial fibrillation, extrasystole, tachy - and bradycardia, sinoatrial and atrioventricular blockade, blockade of the bundle of the bundle, etc.
- pericarditis

3. Control after treatment of listed diseases( medical or cardiosurgical)

Contraindicationsfor carrying out ECG

There are no contraindications for conducting standard electrocardiography. However, the procedure itself can be difficult for people with complex chest injuries, with a high degree of obesity, with severe chest hair( the electrodes simply can not fit tightly to the skin).Also significantly distort the ECG data can the presence of an pacemaker in the heart of the patient.

There are contraindications for ECG with exercise: acute period of myocardial infarction, acute infectious diseases, worsening of the course of arterial hypertension, coronary heart disease, chronic heart failure, complicated rhythm disturbances, suspicion of aortic aneurysm separation, decompensation( deterioration) of diseases of other organs andsystems - digestive, respiratory, urinary. For esophagus ECG, contraindications are diseases of the esophagus - tumors, strictures, diverticula, etc.

Preparation for the

study In the patient's special preparation, ECG does not need to be performed. There are no restrictions in the usual household activities, taking food or water. It is not recommended to drink before the procedure coffee, alcohol or a large number of cigarettes, as this will affect the work of the heart at the time of the study, and the results may be misinterpreted.

How is electrocardiography performed?

ECG can be performed in a hospital or in a polyclinic. In the hospital, patients who have been delivered by an ambulance team with cardiac symptoms or patients already hospitalized in a hospital of any profile( therapeutic, surgical, neurological, etc.) are examined. In the clinic, the ECG is conducted as a planned examination, as well as for patients whose health condition does not require urgent hospitalization in a hospital.

ECG

The patient arrives at the appointed time in the ECG diagnostics room, lies on the couch on his back;The nurse rubs the chest, wrists and ankles with a sponge soaked in water( for better conductivity) and applies electrodes - one "clothespin" on the wrists and feet and six "suckers" on the chest in the projection of the heart. Then the device turns on, the cardiac electrical activity is read, and the result is fixed in the form of a graphical curve on the thermal film with the help of an ink recorder or immediately saved in the doctor's computer. The whole study lasts about 5 - 10 minutes without causing any unpleasant sensations in the patient.

The ECG is then analyzed by a physician for functional diagnostics, after which the conclusion is given to the patient's hands or sent directly to the doctor's office. If the ECG shows no major changes that require further monitoring in the hospital, the patient can go home.

ECD decoding

Now let's take a closer look at the electrocardiogram analysis. Each complex of the normal electrocardiogram consists of the teeth P, Q, R, S, T and segments - PQ and ST.The teeth can be positive( directed upwards) and negative( directed downwards), and the segments above and below the isoline.

The patient will see the following indicators in the ECG protocol:

1. Excitation source. In normal operation of the heart, the source is in the sinus node, that is, the sinus rhythm. Its signs are the presence of positive P teeth in the 11 lead before each ventricular complex of the same form. The non-sinus rhythm is characterized by negative denticles P and appears with sinoatrial blockade, extrasystole, atrial fibrillation, atrial flutter, flicker and flutter of the ventricles.

2. Correctness( regularity) of the rhythm. It is determined when the distance between the teeth R of several complexes differs by no more than 10%.In case the rhythm is wrong, also talk about the presence of arrhythmias. Sinus, but the wrong rhythm occurs with sinus( respiratory) arrhythmia, and sinus rhythm is correct with sinus brady and tachycardia.

3. Heart rate - heart rate. Normally, 60 to 80 beats per minute. The state with heart rate below this value is called bradycardia( slow heart rate), and above - tachycardia( rapid heart rate).

4. Determination of EOS( rotation of the electrical axis of the heart).EOS is the summing vector of the electrical activity of the heart, coinciding with the direction of its anatomical axis. Normally, EOS varies from a semi-vertical to a semi-horizontal position. In obese people, the heart is horizontal, and the leaner is more upright. Deviations of EOS may indicate hypertrophy of the myocardium( proliferation of the heart muscle, for example, in arterial hypertension, heart defects, cardiomyopathies) or conduction disorders( blockade of the legs and branches of the bundle of the Hisnia).

5. Analysis of the tooth R. Zubets P reflects the appearance of a pulse in the sinoatrial node and holding it at the atrium. Normally, the tooth P is positive( the exception is the aVR lead), its width is up to 0.1 sec, and the height is from 1.5 to 2.5 mm. The deformation of the P wave is characteristic for the pathology of the mitral valve( P mitrale) or diseases of the bronchopulmonary system with the development of circulatory failure( P pulmonale).

6. Analysis of the PQ segment. Reflects the performance and physiological delay of the pulse through the atrioventricular node and is 0.02-0.09 sec. The change in duration is typical for conduction disorders - shortened PQ syndrome, atrioventricular blockade.

7. Analysis of the QRS complex. Reflects the pulse on the interventricular septum and ventricular myocardium. Normally its duration is up to 0.1 sec. A change in its duration, as well as deformation of the complex is characteristic of myocardial infarction, blockade of the bundle of the bundle, ventricular extrasystole, paroxysmal ventricular tachycardia.

8. ST segment analysis. Reflects the process of full coverage of the ventricles by excitation. Normally located on the contour, it is allowed to move up or down by 0.5 mm. Depression( decrease) or elevation of ST indicates the presence of myocardial ischemia or the development of myocardial infarction.

9. Analysis of the T wave. Reflects the process of attenuation of the excitation of the ventricles. Normally positive. Negative T also indicates the presence of ischemia or small-focal myocardial infarction.

The patient should remember that an independent analysis of the ECG protocol is not acceptable. Decoding of electrocardiogram indicators should be performed only by the physician of functional diagnostics, cardiologist, therapist or ambulance doctor, as only the doctor during the internal examination can compare the obtained data with the clinical symptoms and the risk of occurrence of conditions requiring treatment, including in the hospital. Otherwise, an underestimation of the ECG conclusion can harm the health and life of a person.

Complications of ECG

Are complications possible during electrocardiography? The procedure for carrying out the ECG is fairly harmless and safe, so complications do not arise. When carrying out an ECG with a load, there may be an increase in blood pressure, the occurrence of rhythm disturbances and conduction in the heart, but this, rather, can be attributed not to complications, but to diseases, for the specification of which provocative samples were prescribed.

Doctor therapist Sazykina O.Yu.