Today, almost everyone over 50 suffers from some kind of cardiovascular disease. However, there is a tendency to rejuvenate these diseases. That is, young people under 35 years old with myocardial infarction or heart failure are increasingly found. Against this background, the knowledge of electrocardiography by doctors is especially relevant.
Einthoven's Triangle is the basis of the ECG. Without understanding its essence, it is impossible 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. In the beginning, you need to understand what an ECG is.
Electrocardiogram
An ECG is a record of the electrical activity of the heart. The definition is given the simplest. If you ripen to the root, then a special device records the total electrical activity of the muscle cells of the heart that occurs when they are excited.
An 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 if it’s emergency hospitalization or planned. A cardiogram is prescribed to everyone during the medical examination, a routine examination of the body in a clinic.
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. A huge contribution to the development of the method of electrocardiography was made by William Einthoven.
Who is Einthoven?
William Einthoven is a Dutch scientist who, at age 25, became a professor and head of the Department of Physiology at Leiden University. 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 the 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.
The most important 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 teeth P, Q, R, S, T. 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 a crucial role in the diagnosis of heart disease.
In 1906, in an article in the medical journal Einthoven described a method for recording ECG from a distance. 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 on the ECG are determined. The ECG of patients with right ventricular hypertrophy with mitral valve insufficiency, left ventricular hypertrophy with aortic valve insufficiency, and various degrees of impulse conduction in the heart were used as examples.
Einthoven's Triangle
In 1913, a scientist in his published article proposed to use 3 standard leads, which are an equilateral triangle, in the center of which is the heart as a source of current, to record an electrocardiogram.
Before building the Einthoven triangle, it is necessary to correctly place the electrodes. The red electrode is connected to the right hand, the yellow is attached to the left, and the green to the left foot. A black, grounding electrode is placed on the right lower limb.
The lines that conditionally connect the electrodes are called lead axes. In the drawing, they are sides of an equilateral triangle :
- I lead - joints of both hands;
- II abduction connects the right arm and left leg;
- III lead - left arm and leg.
Leads record the voltage difference between the electrodes. Each axis of the leads has a positive and negative pole. The perpendicular, dropped from the center of the triangle to the axis of the lead, divides the side of the triangle into 2 equal 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. teeth. If towards the negative pole, then the deviation below the isoline is recorded - Q, S.
Building a triangle
To build the Einthoven triangle with the designation of the leads on a sheet of paper, we draw a geometric figure with equal sides and a vertex pointing down. We put an end to the center - this is the heart.
We mark the standard leads. The upper side is the I lead, on the right - III, on the left - 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, lower the perpendiculars from the point in the center of the triangle on its sides.
The task is to determine the electrical axis of the heart using the Einthoven triangle by ECG.
It is necessary to take a complex of QRS I and III leads, 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 lead I, this is R + Q + S = 13 + (-1) + 0 = 12. In III, this is R + Q + S = 3 + 0 + (-11) = -8.
Then, on the corresponding sides of the Einthoven triangle, we postpone the obtained values. On the top, we count 12 mm to the right of 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 intersection point of these perpendiculars. Now you need to connect the center of the triangle with the resulting point. It turns out the resulting vector of the EMF of the heart.
To determine the electrical axis, you must draw a horizontal line through the center of the triangle. The angle obtained between the vector and the drawn horizontal line is called the angle alpha. It determines the deviation of the axis of the heart. It can be calculated 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.
Determination of EOS allows you to suspect a problem 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 causes of these changes.
Thus, knowledge of the Einthoven triangle, the principles of its construction allows you to correctly impose and connect the electrodes, conduct timely diagnostics, and identify changes in the ECG as quickly as possible. Knowing the basics of an ECG will save many lives.