**The definition of an electrical axis of heart**. The value of the electromotive force of the heart and the direction of the electrical axis of heart change during the whole period of the electric systole heart. The direction of the axis of the heart at any given moment is determined as the torque axis of the heart. Largest teeth ECG in any two standard leads or unipolar from limbs leads you can determine the torque axis any of teeth ECG.

Usually enjoy deciding the direction of the torque axis of the QRS complex.

To do this, set the amount of teeth of the QRS complex in the two leads. Usually use I and III standard leads or increased
single pole leads from the left arm and left leg. The size of a teeth of the QRS complex in a given abstraction is the algebraic sum of his teeth, expressed in millivolts: positive R-wave and the amount of negative teeth Q and S. the direction of the torque axis of the QRS complex use triangle of Eindhoven, the sides of which correspond to the standard leads, and the height is increased unipolar leads from limbs. Height of an equilateral triangle intersect in the center and form a coordinate system for increased SPST leads from limbs. Line SPST leads shifted relative lines standard leads to 30 degrees. It turns out chestiunea coordinate system (Fig. 15).

Fig. 15. Chart to determine the angle of the torque vector of the QRS complex, P and R and planar vector art, AQRS and at.

In addition to determining the torque axis of teeth, ECG, significant importance is the determination of the magnitude and direction of the electromotive force of the heart for the whole period of ventricular excitation (depolarization) and termination of excitation (repolarization) and excitation process fibrillation - secondary axis. For this purpose, define the average electric axis fibrillation on, and P wave, marking it the AP; the average electric axis of ventricular excitation - the QRS complex, labeling it A QRS; average electrical axis of termination ventricular excitation - the T wave, marking it AT.

To determine the average electric axis of teeth ECG measure square relevant teeth. To simplify the calculation teeth is considered as a triangle, and therefore, its area equal to half the works of the base of the triangle at its height. Measure the square in conventional units - millivolt-seconds (MB/sec) with a + if the tooth is directed upwards, and with the sign-if the tooth is directed downwards. The height determined in the mV, and the base is in seconds. The area of the teeth, on the proposal of Almana (R. Ashman), is defined in special units (one unit is equal to 4 MB/sec).

The area of the QRS complex, as its value is the algebraic sum of the squares of positive R-wave and the amount of negative teeth Q and S.

Calculated in units of Almana area of the QRS complex in two leads, determine the average electrical axis of heart on the area of the QRS complex and its torque axis. The area of the QRS is normally around 25 MB/sec. Normal electrical axis of heart-is between 0 and +90 degrees (usually in the range from +20 to +70 degrees). The axis deviation heart from +90 to +180° is defined as the deviation to the right, the deviation from 0 to -90 OC as a deviation to the left. This way you can determine the average electric axis of all teeth ECG.