The electrical axis of the heart (EOS) is one of the main parameters of the electrocardiogram. This term is actively used both in cardiology and in functional diagnostics, reflecting the processes occurring in the most important organ of the human body.
The position of the electrical axis of the heart shows the specialist what exactly happens in the heart muscle every minute. This parameter is the sum of all bioelectric changes observed in the organ. When removing the ECG, each electrode of the system registers the excitation passing at a strictly defined point. If you transfer these values to a conditional three-dimensional coordinate system, you can understand how the electrical axis of the heart is located, and calculate its angle with respect to the organ itself.
How is an electrocardiogram taken?
ECG recording is performed in a special room, which is shielded as much as possible from various electrical noise. The patient is comfortable on the couch with a pillow under his head. To remove the ECG, electrodes are applied (4 on the limbs and 6 on the chest). An electrocardiogram is recorded with calm breathing. In this case, the frequency and regularity of heart contractions, the position of the electrical axis of the heart and some other parameters are recorded. This simple method allows you to determine if there are abnormalities in the work of the body, and if necessary, refer the patient for a consultation with a cardiologist.
What affects the location of the EOS?
Before discussing the direction of the electrical axis, you should understand what constitutes the conductive system of the heart. It is this structure that is responsible for the passage of the pulse along the myocardium. The conduction system of the heart is atypical muscle fibers that connect different parts of the organ. It begins with a sinus node located between the mouths of the vena cava. Further, the impulse is transmitted to the atrioventricular node, localized in the lower part of the right atrium. The next baton is taken by the bundle of His, which quickly diverges into two legs - left and right. In the ventricle, the branches of the bundle of His immediately pass into Purkinje fibers, penetrating the entire heart muscle.
The impulse that has come to the heart cannot escape the conduction system of the myocardium. This is a complex structure with subtle settings, responsive to the smallest changes in the body. For any irregularities in the conductive system, the electrical axis of the heart is able to change its position, which will immediately be recorded on the electrocardiogram.
EOS location options
As you know, a person’s heart consists of two atria and two ventricles. Two circles of blood circulation (large and small) ensure the normal functioning of all organs and systems. Normally, the mass of the left ventricular myocardium is slightly larger than the right. It turns out that all the impulses passing through the left ventricle will be somewhat stronger, and the electrical axis of the heart will be focused on it.
If you mentally transfer the position of the organ to a three-dimensional coordinate system, it becomes clear that the EOS will be located at an angle from +30 to +70 degrees. Most often, such values are recorded on the ECG. The electrical axis of the heart can also be in the range from 0 to +90 degrees, and this, according to cardiologists, is the norm. Why are there such differences?
Normal location of the electrical axis of the heart
There are three main provisions of the EOS. The normal range is from +30 to + 70 °. This option is found in the vast majority of patients who have looked at an appointment with a cardiologist. The vertical axis of the heart is found in thin asthenic people. In this case, the angle will range from +70 to + 90 °. The horizontal axis of the heart is found in short, densely folded patients. In their card, the doctor will mark the angle of EOS from 0 to + 30 °. Each of these options is the norm and does not require any correction.
Pathological location of the electrical axis of the heart
A condition in which the electrical axis of the heart is deflected is not a diagnosis in itself. However, such changes in the electrocardiogram may indicate various violations in the work of the most important organ. The following diseases lead to serious changes in the functioning of the conducting system:
• coronary artery disease;
• chronic heart failure;
• cardiomyopathies of various origins;
• congenital malformations.
Knowing about these pathologies, the cardiologist will be able to notice the problem in time and refer the patient to inpatient treatment. In some cases, when registering an EOS deviation, the patient needs emergency assistance in the conditions of resuscitation.
Deviation of the electrical axis of the heart to the left
Most often, such changes on the ECG are noted with an increase in the left ventricle. This usually occurs with the progression of heart failure, when the organ simply cannot fully perform its function. The development of such a condition with arterial hypertension, accompanied by pathology of large vessels and an increase in blood viscosity, is not excluded . With all these conditions, the left ventricle is forced to work for wear. Its walls thicken, leading to the inevitable violation of the passage of the pulse along the myocardium.
Deviation of the electrical axis of the heart to the left also occurs when the aortic orifice is narrowed. In this case, stenosis of the lumen of the valve located at the outlet of the left ventricle occurs. This condition is accompanied by a violation of the normal blood flow. Part of it lingers in the cavity of the left ventricle, causing it to stretch, and, as a result, densification of its walls. All this causes a natural change in the EOS as a result of improper conduction of the pulse along the myocardium.
Deviation of the electrical axis of the heart to the right
This condition clearly indicates hypertrophy of the right ventricle. Similar changes develop with some respiratory diseases (for example, with bronchial asthma or chronic obstructive pulmonary disease). Some congenital heart defects can also cause an increase in the right ventricle. First of all, it is worth noting stenosis of the pulmonary artery. In some situations, tricuspid valve insufficiency can also lead to the appearance of a similar pathology.
What is the danger of changing the EOS?
Most often, deviations of the electrical axis of the heart are associated with hypertrophy of a particular ventricle. This condition is a sign of a long-standing chronic process and, as a rule, does not require emergency assistance by a cardiologist. The real danger is a change in the electrical axis in connection with the blockage of the bundle of His. In this case, the conduction of the impulse along the myocardium is impaired, which means that there is a risk of sudden cardiac arrest. This situation requires urgent intervention by a cardiologist and treatment in a specialized hospital.
With the development of this pathology, EOS can be rejected both to the left and to the right, depending on the localization of the process. The cause of the blockade can be myocardial infarction, an infectious lesion of the heart muscle, as well as taking certain medications. A conventional electrocardiogram allows you to quickly make a diagnosis, which means that you can give your doctor the opportunity to prescribe treatment, taking into account all important factors. In severe cases, it may be necessary to install a pacemaker (pacemaker), which will send impulses directly to the heart muscle and thereby ensure the normal functioning of the organ.
What to do if the EOS is changed?
First of all, it is worth considering that in itself the deviation of the axis of the heart is not the basis for making this or that diagnosis. The position of the EOS can only give an impetus to a closer examination of the patient. With any changes in the electrocardiogram can not do without consulting a cardiologist. An experienced doctor will be able to recognize the norm and pathology, and also, if necessary, appoint an additional examination. This can be an echocardioscopy for an accurate study of the state of the atria and ventricles, monitoring of blood pressure and other techniques. In some cases, consultation of related specialists is required to resolve the issue of further patient management.
Summing up, several important points should be highlighted:
• The interval between +30 and + 70 ° is considered the normal value of EOS.
• Horizontal (from 0 to + 30 °) and vertical (from +70 to + 90 °) positions of the axis of the heart are valid values and do not indicate the development of any pathology.
• Deviations of the EOS to the left or to the right may indicate various violations in the conduction system of the heart and require specialist advice.
• A change in the EOS detected on the cardiogram cannot be diagnosed, but it is an occasion to visit a cardiologist.
The heart is an amazing organ that ensures the functioning of all systems of the human body. Any changes that occur in it will inevitably affect the work of the whole organism. Regular examinations of the therapist and an ECG will allow you to identify serious diseases in time and avoid the development of any complications in this area.