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 is happening in the heart muscle every minute. This parameter is the sum of all bioelectrical changes observed in the organ. When taking an ECG, each electrode of the system registers excitation passing at a strictly defined point. If we transfer these values to a conditional three-dimensional coordinate system, we 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?
The ECG is recorded in a special room, shielded as much as possible from various electrical interferences. The patient is comfortably positioned on the couch with a pillow under his head. To take an ECG, electrodes are applied (4 onlimbs and 6 on the chest). An electrocardiogram is recorded with quiet 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 functioning of the organ, 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 the conduction system of the heart is. It is this structure that is responsible for the passage of the impulse through the myocardium. The conduction system of the heart is atypical muscle fibers that connect different parts of the organ. It begins with the 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, branches of the bundle of His immediately pass into Purkinje fibers, penetrating the entire heart muscle.
The impulse that came to the heart cannot escape the conduction system of the myocardium. This is a complex structure with fine settings, sensitive to the slightest changes in the body. With any disturbances in the conduction system, the electrical axis of the heart is able to change its position, which will be immediately recorded on the electrocardiogram.
EOS location options
As you know, the human heartconsists 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 myocardium of the left ventricle is slightly larger than that of the right one. In this case, it turns out that all impulses passing through the left ventricle will be somewhat stronger, and the electrical axis of the heart will be oriented precisely towards it.
If you mentally transfer the position of the organ to a three-dimensional coordinate system, it will become clear that the EOS will be located at an angle of +30 to +70 degrees. Most often, these values are recorded on the ECG. The electrical axis of the heart can also be located in the range from 0 to +90 degrees, and this, according to cardiologists, is also the norm. Why are there such differences?
Normal location of the electrical axis of the heart
There are three main provisions of EOS. The normal range is from +30 to +70°. This variant occurs in the vast majority of patients who visit a cardiologist. The vertical electrical axis of the heart is found in thin asthenic people. In this case, the angle values will range from +70 to +90°. The horizontal electrical axis of the heart is found in short, densely built patients. In their card, the doctor will mark the EOS angle 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 in itselfis a diagnosis. However, such changes on the electrocardiogram may indicate various disorders in the work of the most important organ. The following diseases lead to serious changes in the functioning of the conduction system:
• ischemic heart disease;
• chronic heart failure;
• cardiomyopathy of various origins;
• birth defects.
Knowing about these pathologies, a cardiologist will be able to notice the problem in time and refer the patient to inpatient treatment. In some cases, when registering a deviation of the EOS, the patient needs emergency assistance in intensive care.
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 happens with the progression of heart failure, when the organ simply cannot fully perform its function. It is not excluded the development of such a condition in arterial hypertension, accompanied by pathology of large vessels and an increase in blood viscosity. In all these conditions, the left ventricle is forced to work hard. Its walls thicken, leading to the inevitable violation of the passage of the impulse through the myocardium.
Deviation of the electrical axis of the heart to the left also happens when the aortic mouth narrows. In this case, there is a stenosis of the lumen of the valve located at the outlet of the left ventricle. This condition is accompanied by a violation of the normalblood flow. Part of it lingers in the cavity of the left ventricle, causing it to stretch, and, as a result, compaction of its walls. All this causes a regular change in the EOS as a result of improper conduction of the impulse through the myocardium.
Deviation of the electrical axis of the heart to the right
This condition clearly indicates right ventricular hypertrophy. Similar changes develop in some respiratory diseases (for example, in bronchial asthma or chronic obstructive pulmonary disease). Some congenital heart defects can also cause an enlarged right ventricle. First of all, here it is worth noting stenosis of the pulmonary artery. In some situations, tricuspid valve insufficiency can also lead to 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 one or another ventricle. This condition is a sign of a long-standing chronic process and, as a rule, does not require emergency help from a cardiologist. The real danger is the change in the electrical axis in connection with the blockade of the bundle of His. In this case, the conduction of the impulse along the myocardium is disrupted, 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 deviated both to the left and to the right, depending on the localization of the process. The reason for the blockademyocardial infarction, infectious damage to the heart muscle, as well as taking certain drugs can become. A conventional electrocardiogram allows you to quickly make a diagnosis, and therefore, enable the doctor 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 if the EOS is changed?
First of all, it is worth considering that the deviation of the axis of the heart in itself is not the basis for making a particular diagnosis. The position of the EOS can only give impetus to a closer examination of the patient. With any changes in the electrocardiogram, one cannot do without consulting a cardiologist. An experienced doctor will be able to recognize the norm and pathology, and, if necessary, prescribe an additional examination. This may be echocardioscopy for a targeted study of the state of the atria and ventricles, blood pressure monitoring and other techniques. In some cases, consultation of related specialists is required to decide on the further management of the patient.
Summing up, several important points should be highlighted:
• The normal value of EOS is the interval from +30 to +70°.
• Horizontal (from 0 to +30°) and vertical (from +70 to +90°) positions of the heart axis are acceptable values and do not indicate the development of any pathology.
• EOS deviations to the left orto the right may indicate various disorders in the conduction system of the heart and require specialist advice.
• The change in the EOS, revealed on the cardiogram, cannot be set as a diagnosis, but is a reason to visit a cardiologist.
The heart is an amazing organ that ensures the functioning of all systems of the human body. Any changes occurring in it inevitably affect the work of the whole organism. Regular examinations of the therapist and the passage of an ECG will allow timely detection of the appearance of serious diseases and avoid the development of any complications in this area.
