The problem of electrocardiography is the most complete and accurate registration of EDS heart.

**Standard lead**. During the ECG registration impose electrodes on the following three points of the surface of the body: the right arm (arm), left arm and left leg (tibia). The potential difference of the left and the right hand is defined as I abstraction, left leg and right arm, as II abstraction, left foot and left hand - III as abstraction. These lead was named standard and are indicated by Roman numerals.

Form ECG depends on the method of accession to the poles of the electrocardiograph. Upward teeth ECG I lead out, when the electrode left hand is positive with respect to the electrode right hand, in the second abstraction - when the electrode left leg positive towards the electrode right hand in the third lead - when the electrode left leg positive towards the electrode left hand.

According to the proposal of Eindhoven and other human body can schematically be likened, given the potential distribution on its surface, an equilateral triangle in the center of which is a source of electrical energy in the form of a dipole. This right corner R displays the capacity of the right hand, left corner of the L - potential of the left hand, and the lower corner of the F - potential of both legs, given that the potentials of the feet are almost equal. Then abstraction from R and L will meet I abstraction, from R and F - II abduction, as from L and F - III abstraction (Fig. 5).

In the centre of the triangle at a point in the same vertical plane that point R,L, F, and at the same distance from them is a source of EMF - heart. The arrow shows the direction of the electrical axis of heart from negative to positive. Electrical axis of heart indicates the direction of his electromotive force. Line electrical axis of heart at the intersection with the line R - L, i.e. with the direction I lead, forms an angle. The value of this angle determines the direction of the electrical axis of heart. The value of the electromotive force of the heart F can be represented schematically in the form of arbitrary value of the segment (arrows) P - Q. If to consider that the human body is a homogeneous conductor, i.e. the resistance of all tissues and organs of the human body is the same, you can determine the portion of EDS, which is captured in each of the three leads.

I lead in the direction of the electrical axis of heart, that is, when the value of the angle a, captured the part EMF heart that is projected on the line R - L. To obtain such projection of points P and Q omit the perpendiculars on line R - L. the Size of the segment p1 q2 is thus characteristic of force (et), caught in the I lead.

In the second lead is captured that part of the EMF of the heart to the heaven projected on line R - F. To determine lower on line R - F perpendiculars from the points P and Q; the segment P2 - q2 is a characteristic of the EMF heart (e2), caught in the II abstraction.

In the third lead was detected that part of the EMF heart that is projected on line L - F. Perpendiculars on this line of points P and Q, give segment p3 - q3, which characterizes the EMF (E3), caught in the third lead.

The scheme allows you to set the equation E2=E1+E3. This indicates that the magnitude of the EMF, captured in the second abstraction, equal to the sum of EMF, captured in the I and III leads. From this diagram it is evident also that the EMF, and therefore, the value of teeth in standard leads, due to the direction of the electrical axis of heart, i.e. the angle of?.

The algebraic sum EMF registered three standard leads, according to the scheme at any given moment is equal to zero.

All these definitions are precise, if we consider that the human body is rounded vessel in the center of which is the heart that others heart tissues and organs are homogeneous mass with the same resistance that the distance between your right hand, left hand and left leg the same and is equal to the distance at which any of these electrodes from the heart, the heart and limbs are on the same vertical plane.

Actually it is not so, and all calculations are not quite accurate. However, the error of these calculations on test data, not very big, and the scheme proposed by Antivenom, use and now for various calculations.

- Chest leads
- Single pole diversion from limb
- Esophageal lead
- Intracavitary (vnutribrjushinnye and intraventricular) lead
- Radio (the body) electrocardiography
- Normal ECG
- Atrial ECG complex
- Ventricular complex
- The definition of an electrical axis of heart
- Ventricular gradient
- Effect on ECG various physiological factors