Effect on ECG various physiological factors

Every change of position of the heart caused by rotating it around three axes: the front to the rear (sagittal), longitudinal (long) and transverse (horizontal). The magnitude and direction of teeth ECG in various derivations electric determine the position of the heart (Fig. 16).

Fig. 16. Scheme of turning the hearts around the various axes. Arrows indicate the direction of rotation of the heart and around the anterior-posterior axis; b - around the long axis; around the cross axis.

When turning the hearts around the anterior-posterior axis (Fig. 16, a) heart takes either a horizontal or vertical position that gets the most clearly visible in standard leads. The horizontal position of the heart causes the rejection of its axis to the left, and a vertical position to the right. Horizontal and vertical position of the heart gets reflected in unipolar leads from limbs (see above).
Turn the hearts long (longitudinal) axis (Fig. 16, b) occurs both clockwise and in the opposite direction and also causes changes in the ECG in all leads. This turn is observed in the number of physiological processes: change of position of a body, the act of breathing, physical stress, etc.
With the turning of the hearts around the transverse (horizontal) axis is offset the apex of the heart or anterior or posterior (Fig. 16 in). Turn the hearts around the transverse axis reflected in the single-pole leads from limbs.
Wilson proposed to define the electrical position of the heart to the teeth unipolar chest leads and leads from limbs. When electrocardiography there are 5 positions heart: vertical, polovitkina, intermediate, is semi horizontal and horizontal.
Vertical electric position of the heart (the angle and equal to +90 degrees) form of the QRS complex in unipolar lead from the left hand is similar to that observed in right-wing positions chest leads, but the form of the QRS complex in unipolar lead from the left leg is observed in the left position of the chest leads (Fig. 17).

Fig. 17. Electrocardiogram person with a healthy heart in the standard chest and increased unipolar leads from limbs vertical position of the heart in the chest (the designations are the same as in Fig. 11): 1 - right ventricle; 2-the left ventricle.

When polovitkina position (angle of? is equal to +60 degrees) the form of the QRS complex in unipolar lead from the left foot is similar to that observed in the left position of the chest leads.
In an intermediate position of the heart (the angle and equal 4-30 degrees) form of the QRS complex in unipolar lead from the left hand and the left foot is similar to that observed in the left position of the chest leads.
When is semi horizontal position of the heart (the angle is 0 degrees) form of the QRS complex in unipolar lead from the left hand is similar to that observed in the left position of the chest leads.
When the horizontal position of the heart (the angle of? equal to-30oC) the form of the QRS complex in unipolar lead from the left hand is similar to that observed in the left position of the chest leads, but the form of the QRS complex in unipolar lead from the left leg is observed in the right positions chest leads (Fig. 18).

Fig. 18. Electrocardiogram person with a healthy heart in the standard, thoracic and increased unipolar leads from the limbs in a horizontal position of the heart (the designations are the same as in Fig. 11): 1 - the right atrium; 2 - right ventricle; 3 - left ventricle.

In cases where there is no similarity between unipolar breast leads and unipolar derivations from the limbs, electric position of heart indefinable. The data of x-ray studies have shown that the ECG is not always accurately reflect the position of the heart.
ECG is recorded usually lying down on his back.
Various provisions of the surveyed (vertical, horizontal, on the right or left side), changing the position of the heart, cause a change of teeth ECG.
In the vertical position, the number of heart rate increases, the electrical axis of heart moves to the right. This causes corresponding variations in the magnitude and direction of teeth, standard ECG and chest leads. The QRS duration decreases. The value of the T wave decreases, especially in the II and III leads. Segment RS-T in these leads several shifts to the bottom.
While standing on the right side is the rotation of the electrical axis of heart around the long axis counterclockwise, and at the position on the left side - clockwise with the corresponding changes in the ECG.
The form and direction of teeth ECG in children differs from the ECG adult. In old age, the teeth of the R and T is often reduced. The sample interval, P-Q, and QRS usually on the upper limit of normal. With age significantly bowl observed deviation of the electrical axis of heart left. Systolic index is often slightly increased compared with due.
Women amplitude of teeth, P, T and QRS complex slightly less in standard and chest leads. Often there is a shift of segment RS-T and negative tooth T in the third lead.
The area of the teeth of the QRS complex less. Ventricular gradient less and rejected more to the left, prong U more. The interval P-Q and QRS complex on average less. The duration of the electric systole and systolic indicator more.
The overwhelming effect on heart parasympathetic nervous system, the number of heart rate decreases. Prong R decreases, occasionally blurred increases. The interval P-Q is slightly increasing. The question about the effect of parasympathetic division for the T wave cannot be considered completely understood. According to some data, the T wave decreases, on the other - is increasing. Cut Q-T is often reduced.
The overwhelming impact on the heart of the sympathetic Department of the vegetative nervous system, the number of heart rate increases. Prong R usually increases, sometimes decreases. The interval P-Q is reduced. The the T wave, according to one, increasing in others is reduced.
Positive emotions have little effect on ECG. Negative emotions (fear, fright, and others) cause the increase of heart, for the most part the increase, and sometimes decrease of teeth.
During a deep breath due to a shift down in the diaphragm heart takes a vertical position. Electrical axis of his moves to the right, with all the resulting changes in EKG. Affects the shape of teeth, ECG and increased pressure on the heart during inspiration of the sympathetic Department of the vegetative nervous system. During a deep exhalation ECG changes caused by the lifting of the diaphragm, the deviation of the electrical axis of heart left and the dominant influence on the heart parasympathetic nervous system.
Under normal breathing these changes ECG is insignificant.
Physical stress can cause ECG changes in different ways: to influence reflex on depolarization and repolarization heart, reflex and directly on conduction system and the contractile myocardium. Usually these paths are combined. ECG changes depend on the degree and duration of action of these factors.
Marked changes teeth ECG observed after significant physical stress: increasing and sometimes blurred the broadening, and P wave; the reduction of the duration of the interval P-Q, and sometimes offset down due to the layering segment of the P-TA; a slight reduction in the duration of the QRS complex and often reject electrical axis of heart right, as well as the offset down segment RS-T; the increase of the T wave, reduced the segment of the Q-T is proportional to the increase of heart; the emergence of increased wave U.
Large quantities of food is increasing heart rate and decrease of the T wave (sometimes significant, up to jump in the negative) in the II and III leads. Sometimes there is a slight increase, and P wave, increase of a segment of the Q-T and systolic indicator.
These changes ECG reach a peak within 30-60 minutes after meals and after 2 hours disappear.
ECG changes during the day in healthy people insignificant and concern teeth So the T Wave reaches a maximum in the early morning, and after Breakfast the size of its smallest.