Electrocardiography

Cyclic activity of the heart is accompanied by the appearance of electrical potentials. Electrocardiography allows recording these potentials from the body surface. The resulting graphic representation of the oscillations of electrical potentials is called an electrocardiogram.

Electrocardiography is the main method of instrumental diagnostics of various cardiac disturbances: myocardial infarction, various forms of coronary heart disease, heart rhythm disturbances and conduction.

Observation of certain ECG changes in dynamics allows to recognize myocarditis, pericarditis, myocardial dystrophy, and some other types of heart pathology.

ECG recording devices - electrocardiographs - have an input device, sensing potentials from the body surface of the subject, electronic amplifier and a recorder.

There are several types of electrocardiographs, which are delineated as follows.

1. By the number of registration channels:

• single-channel devices, usually portable, portable;

• multi-channel, used in hospital.

2. By type of power supply:

• network;

• battery( battery);

• universal.

research technique In the diagnostic practice, electrocardiographs are used. From the electrocardiograph go wires to the electrodes( "patient cable"), which are imposed at certain points on the subject. The skin of the patient at the electrode application points is treated with cotton wool soaked in alcohol. Electrodes are lubricated with an electrically conductive paste or gauze pieces moistened with an isotonic solution of sodium chloride are used as gaskets.

Before carrying out the research, the nurse must ensure that the electrocardiograph is functioning correctly, the electrodes are not broken, there is no missing wire in the device.

When working with an electrocardiograph, it is important to remember the safety precautions: grounding the device, the metal couch on which the patient is lying, do not carry out the procedure if there are wires on the wires, finding electrodes in the vicinity of the wiring or any other cables currently receiving power from the network.

After the examination, the electrode paste is removed from the skin of the patient, wiping dry with a napkin, and the electrodes are washed with a soft brush and soap under a stream of warm water.

Electrocardiographic leads

The specific location of the electrodes for recording the ECG is called an abduction. With single-pole lead recording is most often performed on electrode materials. With standard leads, the recording is made from a pair of electrodes located on both hands or on the arm and left leg.

To unify the studies, the wire of each electrode is marked, and the electrocardiograph is equipped with a switch allowing selection of leads within a conventional 12-lead system.

Guided by the color markings, the red electrode is applied to the right arm, the yellow electrode to the left( to the wrist), the green to the left leg, the black electrode to the right( to the skin of the lower legs).From these electrodes, the ECG is recorded in six leads - three standard( I, II, III) and three unipolar from the extremities: from the right hand( aVR), from the left arm( aVL) and from the left leg( aVF).The other six leads( thoracic, or pericardial) are considered unipolar, recorded from electrodes that are attached at six points on the skin of the chest at a specific location:

• V1 - IV intercostal space near the right edge of the sternum;

• V2 - IV intercostal space near the left edge of the sternum;

• V3 - in the middle of the line passing between the location of the electrodes V2 and V4;

• V4 - on the left sredneklyudichnoy line at the height of V intercostal space;

• V5 - at the height of the V4 electrode on the left anterior axillary line;

• V6 - at the same level on the left middle axillary line.

All thoracic leads transmit the electrical activity of the myocardium,

located mainly near the electrode of the left ventricular sections of the heart:

• V1 - septa;

• V2-V3 - the front wall;

• V4 - areas of the apex;

• V5 -V6 - side wall.

Biopotentials from the upper sections of the lateral wall and from the diaphragmatic site of the posterior wall are accurately transferred to the ECG in single-pole leads from the extremities, mainly aVL and in aVF