Today, almost every person over 50 suffers from some form of cardiovascular disease. However, there is a trend of rejuvenation of these diseases. That is, more and more young people under 35 years of age with myocardial infarction or heart failure. Against this background, doctors' knowledge of electrocardiography is especially relevant.
Einthoven's triangle is the basis of the ECG. Without understanding its essence, it will not be possible to correctly place the electrodes and decipher the electrocardiogram qualitatively. The article will tell you what it is, why you need to know about it, how to build it. First you need to understand what an ECG is.
Electrocardiogram
ECG is a recording of the electrical activity of the heart. The definition given is the simplest. If you look at the root, then a special device records the total electrical activity of the muscle cells of the heart that occurs when they are excited.
Electrocardiogram plays a leading role in the diagnosis of diseases. First of all, of course, it is prescribed for suspected heart disease. In addition, an ECG is necessary for everyone who enters the hospital. And it doesn't matter, it's an emergency hospitalizationor planned. A cardiogram is prescribed for everyone during a medical examination, a routine examination of the body in a polyclinic.
The first mention of electrical impulses appeared in 1862 in the works of the scientist I. M. Sechenov. However, the ability to record them appeared only with the invention of the electrometer in 1867. William Einthoven made a huge contribution to the development of the electrocardiography method.
Who is Einthoven?
William Einthoven is a Dutch scientist who at the age of 25 became a professor, head of the department of physiology at the University of Leiden. It is interesting that initially he was engaged in ophthalmology, conducted research, wrote a doctoral dissertation in this area. Then he studied the respiratory system.
In 1889, he attended an international congress on physiology, where he first became acquainted with the procedure for conducting electrocardiography. After this event, Einthoven decided to come to grips with improving the functionality of the device that records the electrical activity of the heart, as well as the quality of the recording itself.
Major discoveries
During the study of electrocardiography, William Einthoven introduced many terms that the entire medical community uses to this day.
The scientist was the first to introduce the concept of P, Q, R, S, T waves. Now it is difficult to imagine an ECG form without an accurate description of each of the teeth: amplitude, polarity, width. Determination of their values, relationships among themselves plays an important role in the diagnosis of heart disease.
In 1906, in an article in the medical journal, Einthoven described a method for recording an ECG ondistance. In addition, he revealed the existence of a direct relationship between changes in the electrocardiogram and certain heart diseases. That is, for each disease, characteristic changes in the ECG are determined. As examples, the ECG of patients with right ventricular hypertrophy with mitral valve insufficiency, left ventricular hypertrophy with aortic valve insufficiency, various degrees of blockade of impulse conduction in the heart were used.
Einthoven's Triangle
In 1913, a scientist in his published article suggested using 3 standard leads to record an electrocardiogram, which are an equilateral triangle, in the center of which is the heart as a current source.
Before constructing the Einthoven triangle, it is necessary to place the electrodes correctly. The red electrode is connected to the right arm, the yellow electrode is attached to the left, and the green electrode is attached to the left leg. A black, grounding electrode is placed on the right lower limb.
The lines that conditionally connect the electrodes are called the lead axes. In the drawing, they represent the sides of an equilateral triangle:
- I abduction - connections of both hands;
- II lead connects right arm and left leg;
- III lead – left arm and leg.
Leads register the voltage difference between the electrodes. Each lead axis has a positive and a negative pole. The perpendicular, dropped from the center of the triangle to the axis of abduction, divides the side of the triangle into 2equal parts: positive and negative. Thus, if the resulting vector of the heart deviates towards the positive pole, then on the ECG the line is recorded above the isoline - P, R, T waves. If towards the negative pole, then a deviation below the isoline is recorded - Q, S.
Building a triangle
To build Einthoven's triangle with the designation of leads on a sheet of paper, draw a geometric figure with equal sides and a vertex pointing down. In the center we put a dot - this is the heart.
Note the standard leads. The upper side is lead I, on the right is lead III, on the left is lead II. We denote the polarity of each lead. They are standard. They need to be learned.
Einthoven's triangle is ready. It remains only to use it for its intended purpose - to determine the electrical axis of the heart and the angle of its deviation.
Determination of the electrical axis of the heart
The next step is to determine the center of each side. To do this, you need to lower the perpendiculars from the point in the center of the triangle to its sides.
The task is to determine the electrical axis of the heart using the Einthoven triangle on the ECG.
It is necessary to take the QRS complex of leads I and III, determine the algebraic sum of the teeth in each lead by counting the number of small cells of each tooth, taking into account their polarity. In Iin abduction it is R+Q+S=13 + (-1) + 0=12. In III it is R + Q + S=3 + 0 + (-11)=-8.
Then, on the corresponding sides of the Einthoven triangle, we set aside the obtained values. On the top, we count 12 mm to the right from the middle, towards the positively charged electrode. On the right side of the triangle, we count -8 above the middle - closer to the negatively charged electrode.
Then from the obtained points we build perpendiculars inside the triangle. Mark the point of intersection of these perpendiculars. Now you need to connect the center of the triangle with the formed point. The resulting vector of the EMF of the heart is obtained.
To determine the electrical axis, draw a horizontal line through the center of the triangle. The angle obtained between the vector and the drawn horizontal line is called the alpha angle. It determines the deviation of the axis of the heart. You can calculate it using a conventional protractor. In this case, the angle is -11°, which corresponds to a moderate deviation of the axis of the heart to the left.
The definition of EOS allows you to suspect a problem that has arisen in the heart in time. This is especially true when compared with previous films. Sometimes a sharp change in the axis in one direction or another is the only clear sign of a catastrophe, which allows you to assign other methods of examination to identify the cause of these changes.
Thus, knowledge of Einthoven's triangle, ohprinciples of its construction allows you to correctly apply and connect electrodes, conduct timely diagnostics, and identify changes in the ECG as soon as possible. Knowing the basics of an ECG will save many lives.
