Part Three

- Normal heart drawing

First, the electrocardiogram (ECG) means an electrocardiogram (electrocardiogram).

Diagnosing diseases depends mainly on taking a good look at the patient’s condition first, in addition to doing some tests. The EKG device confirms the diagnosis of many disease conditions, and in some cases it is very important for treatment.

An EKG is very important in diagnosing many conditions, including:

1. Changes in the regular rhythmic heartbeat.

2. It helps diagnose the cause of chest pain.

3. The use of thrombolytics in cases of myocardial infarction depends on the electrocardiogram.

4. It also helps in diagnosing the cause of shortness of breath (breathlessness).

So that you do not get lost from the topic, we will talk about the topic of drawing the heart in the following order:

First: We will talk about electrocardiography and how the heart beats.

Second: We will talk about the EKG device, how to make an EKG, and its pictures.

Third: We will discuss the topic of what we will read in the EKG paper.

First: electrocardiogram

The contraction of any muscle is accompanied by electrical currents called depolarization, and these currents can be recorded using electrodes. These electrodes are connected to the surface of the body. Therefore, we can record the contraction of the muscles of the entire body.

Therefore, if we want to record the contraction of only the heart muscles clearly, the person must be relaxed and all the other muscles of his body must be relaxed.

Although the heart contains 4 chambers, we will see in the electrocardiogram that there are only two chambers because the atria contract together and the ventricles as well.

Normal pulse

• The regular rhythmic heartbeat originates from within the tissue of the heart muscle itself. It is self-moving, as the normal pulse begins with an electrical signal issued by a specialized, very small neuromuscular electrical generator and regulator located in the wall of the right atrium called the sinoatrial node, or sinoatrial node. At a rate of 60-100 pulses/electrical signal per minute, this electrical signal spreads very quickly to the atria, causing them to contract to push the blood from the atria to the ventricles. Then this electrical signal is transmitted to a receptor. In the same case, it is considered a very small backup generator located between the ventricles and the atria, and it is called the “node.” Atrioventricular (or () which allows the electrical signal to pass through electrical connections that branch from the atrioventricular node to the ventricles in a fraction of a second, which makes them contract to push blood from the ventricles out of the heart. The right ventricle pushes deoxygenated blood to the lungs to be oxidized, and the left ventricle pushes oxygenated blood to all... Parts of the body to benefit from the oxygenated blood that returns after the oxygen has been removed from it to the right part of the heart, thus completing one division of blood.

• Electrocardiogram

• Thus, in normal humans, the electrical signals originate from the (sinoatrial node), and at this time the system is called (cardiac rhythm) or (sinus rhythm), but in some pathological cases, the currents can arise from another source, such as (the atrioventricular node), and it is called The system at this time is called (nodal rhythm) or (nodal rhythm), or it may originate from any other source, such as the muscles of the ventricle itself, and this may be due to the failure of the sinoatrial node to issue pulses or the presence of an external source - anywhere else in the heart - that beats. At a rate higher than the primary pacemaker, it takes its place. Therefore, in a normal person, the electrical signals originate from the sinoatrial node, and at this time the system is called the “cardiac rhythm” or “sinus rhythm.” However, in some pathological cases, the currents can arise from another source, such as (Atrioventricular node) The system is called at this time (nodal rhythm) or (nodal rhythm), or it may stem from any other source, such as the muscles of the ventricle itself, and this may be due to the failure of the sinoatrial node to issue impulses or the presence of an external source - in Anywhere else in the heart - beats at a higher rate than the primary pacemaker and takes its place.

• EKG pictures (leads)

Each electrode connected to the body is considered a camera, and we place 10 electrodes on the human body, one on each arm and each leg, and at six points on the chest. Thus, we obtain 10 electrodes (cameras) from different directions. Each camera produces a different image for us from the other camera, because each One captures the view of the heart from a different angle, but it is the same view, like a football match. We find that there is more than one camera on the field, and each one captures a specific view from a specific angle, but it is.

• The EKG device produces 12 images for us

• The six electrodes (cameras) on the chest produce 6 different images (leads) for us and are called

V1,V2,V3,V4,V5,V6

• The locations of the electrodes on the chest are as follows:

• V1: In space No. 4 between the ribs on the right

Rt. 4th intercostal space

V2: In the space number 4 between the ribs on the left

• Lt.4th intercostal space

• V3: At the point between V2 & V1

V4: At the apex of the heart APEX

V5: At the same level as the apex of the heart at the anterioer axillary line

V6: At the same level as the apex of the heart at the mid-axillary line

Link locations:

• As for the electrodes on the ends, each one produces an image for us, except for the one at the left leg, which is only for ground connection and does not interfere in the drawing.

For example: In the right hand, it is called: aVR

• The one on the left hand: aVL

• And the one at the right foot: aVF

• 3. As for the remaining three images, they are a fusion of each of the two images resulting from the poles located at the edges

For example: merging the image resulting from the camera (the electrode) located at the right hand with the other located at the left hand produces an image called:

(lead I).

• Also, the image of the right hand with the foot is called: (lead II).

• Also, the image of the left hand with the foot is called: (lead III)

• Since these images are a combination of more than one image, they are therefore magnified. In order for the resulting images to be all equal, the device enlarges the other images issued by the parties.

(aVR, aVL, aVF).

• Where the letter (V) means the word (Vector), meaning the electrode to which the camera is directed).

• The meaning of the word (a) is (augmented), meaning magnified, as we explained.

• The meaning of the word (R) is (Right arm).

• The meaning of the word (L) is (Left arm).

• And from me the word (F) is Foot).

• The pictures are arranged as follows (from left to right, of course):

• Lead I, lead II, lead III, aVR, aVL, aVF, V1,V2,V3,V4,V5,V6))-

EKG shape

• It is known that the muscles of the atria are very small when compared to the muscles of the ventricles, and therefore the electrical current accompanying the contraction of the atria will be small and is symbolized in the electrocardiogram by the symbol (P wave), while the contraction of the ventricles is symbolized by the symbol (QRS group) ( QRS complex), and then the relaxation of the ventricles is symbolized by the symbol (T wave), since the cardiac division begins with the contraction of the atria, then their relaxation, then the contraction of the ventricles, then their relaxation, and all of this is recorded as waves on the electrocardiogram paper...

In order of events:

• 1. Atrial contraction (P wave).

• 2. Then they relax (-) – and here the atria’s relaxation is not recorded because it occurs at the same time as the ventricles’ contraction, and therefore the ventricles’ contraction hinders the recording of the atria’s relaxation.

• 3. Then the ventricles contract (QRS complex).

• 4. Then they expand (T wave).

• For the QRS group, the first curvature down the straight line is called (Q wave) and the subsequent curvature upward is called (R wave) and it may be preceded by (Q wave) or not, then It is followed downward by another curvature called the S wave, which may also be preceded by a Q wave or no... That is, it is not necessary for the ventricular contraction to be represented by the entire QRS group.

• Any change in these images reveals a problem that may be in the heart rate or the result of a blocked artery or something else, but the most widely used and clearest images are (lead II) and (avR), and one of them is used to monitor the patient’s condition in care units. Concentrated, although the most widely used is (lead II

Conclusion:

• There are 10 electrodes (cameras) - they are placed on the chest, legs, and arms... They produce 12 images (leads), which are as follows:

• (Lead I, lead II, lead III, aVR, aVL, aVF, V1,V2,V3,V4,V5,V6).

• In each of these images we find some curves symbolizing the division of the heart:

• Atria contraction: (P wave).

• Their simplicity: (-).

• Ventricular contraction: (QRS complex).

• Their relaxation: (T wave)...

Important rule:

• If the direction of the electric current in the heart is in the same direction as the directing electrode (camera), then the result will be a negative (downward) curvature on the EKG paper, and vice versa, if the direction of the current is opposite the direction of the camera, then the result will be a positive (upward) curvature on the EKG paper, and that The direction of the current has nothing to do with the direction of the camera, so the signal (curvature) has any shape.

• Therefore, we find that most of the (lead II) curvatures are positive (upward) because the directed electrode (camera) is filming in the opposite direction of the current, while the (avR) curvature is downward because the directing camera is filming in the direction of the current.

• After reading the electrocardiogram, you must write a report on each of the following:

• 1. Heart rate/minute.

• 2. Heart rate rhythm (regular or not).

• 3. Cardiac axis imbalance.

• 4. Signs of ischemia.

• 5. P wave.

• 6. P-R interval(

• 7. QRS complex.

• 8. T wave().

• 9. ST segment

Heart rate and rhythm

• The EKG device picks up electrical currents and records them on graph paper with equal-sized squares at a regular rate. EKG paper contains large squares, and each large square contains 25 small squares (5 x 5), and each small square (1 mm) represents 0.04 seconds. Therefore, each large square (5 mm) represents 0.2 seconds, meaning that 5 large squares represent (1 second) and 300 large squares represent (1 minute).

• We can calculate the heart rate per minute. For example, if we find the complete heart division, each large square is repeated, meaning that the heart beats at a rate of 300 beats/minute, and so on...

Therefore, measuring the distance between (R waves) and each other - given that it is the highest point in the drawing - represents the heart rate. The distance between (interval R-R) represents the time it takes to conduct electrical currents through parts Different heart

• Therefore, the heart rate can be measured as follows:

• Heart rate = 300 (300 squares to calculate the number of heart beats per minute) ÷ the distance between (AR-AR), but this is if the heart rate is moving at a regular rhythm....

• Rhythm is measured by matching the distance between (R-R), which is equal in all images.

• If the rhythm is irregular, we will calculate the heart rate as follows

Heart rate and rhythm

• Therefore, the heart rate can be measured as follows:

• Heart rate = 300 (300 squares to calculate the number of heart beats per minute) ÷ the distance between (AR-AR), but this is if the heart rate is moving at a regular rhythm....

• Rhythm is measured by matching the distance between (R-R), which is equal in all images.

• If the rhythm is irregular, we will calculate the heart rate as follow

• Irregular electrocardiogram

• Heart rate=

• Number of R waves

• Within 6 seconds x 10

• Of course, this calculation is done over the length of the EKG images for 6 seconds.

• P wave:

• Period: It represents the period of atria contraction.

• Duration: equal to 0.08_0.12 seconds, i.e. (2-3) small squares, and sometimes it is said to be (2.5 x 2.5) small squares, length by width.

• Shape: semicircular, symmetrical and in an upright position in the image (lead II) and upside down in (avR), as we mentioned previously.

Conditions that can be diagnosed from differences in the P wave:

• Enlargement of the right atrium, the most common cause of which is pulmonary hypertension:

• It is diagnosed by an increase in the height (length) of the (B) wave of more than 3 mm as a result of an increase in the period of contraction of the right atrium due to its large size, and because one of its most famous causes is high pulmonary pressure (Pulmonary hypertension), so it is called (P wave) by the name (P-Palmonale).

• The enlargement of the left atrium, the most common cause of which is mitral stenosis:

• It is diagnosed by an increase in the width of the B wave more than (0.11 seconds) as a result of an increase in the period of contraction of the left atrium due to its large size, and because one of its most famous causes is mitral stenosis, so it is called

• (P wave) as (P-Mitral).

· Atrial fibrillation

• and that is through:

The absence of the B wave (P wave) and its replacement by small fibrillatory waves, which are called the B wave at this time (F waves).

• Irregularity of the distance between R waves (R-R interval).

• 4- It is also possible to diagnose atrial flutter:

• By replacing (wave B) with flutter waves, which are shaped like saw teeth.

• 5- If the electrical signals originate from (the atrioventricular node)

• Nodal rhythm, not my heart rhythm, comes from (the sinoatrial node) as usual, and as we talked about previously, this may be due to the failure of the sinoatrial node (temporary or permanent failure) to issue pulses or the presence of an external source elsewhere in the heart that beats at a rate higher than The primary pacemaker (sinoatrial node) takes its place, and here it can be diagnosed through an inversion (wave B), where when (the atrioventricular node) is the source of the electrical signals, the direction of the electrical current changes and becomes in the same direction as the electrode (camera). Therefore, the B wave appears inverted (downward curvature) in (lead II) and upward in (avR)... Return to the base!!

• Third: P-R interval:

• It starts from the beginning of (wave B) to the beginning of (QRS group), that is, from beginning to beginning, and it represents the time it takes for the electrical current to travel from the sinoatrial node to the atria and from there to the ventricles.

• It is equal to = 0.12_ 0.20 seconds, which is (3-5) small squares.

Conditions that can be diagnosed from differences that occur at this distance

• : (tachycardia) palpitations (rapid heartbeat).

• The distance is shorter than the normal distance

• 2- Bradycardia:

• The distance is longer than the normal distance

(Heart block): Heart block

• In the first degree of cardiac arrest:

• The usual length of distance increases.

• In the second degree:

• The length of the distance increases gradually, followed by its absence (QRS group), then it returns to normal again, and so on.

• In the third degree:

• The QRS group overlaps with (wave B), and the QRS group exists in different forms

Fourth: QRS complex

• Period: represents the time it takes for the current to travel through the ventricles.

• Duration: equals = 0.12 seconds (3 small squares).

• Diagnosis: As we mentioned, it helps diagnose cases of atrial and ventricular fibrillation, atrial flutter, and other types of heart rhythm disorders.

It also helps in diagnosing angina and stroke, as we will explain, and other heart diseases.

Fifth: Cardiac Axis

• An imaginary line drawn on the heart representing the resultant electrical current, as the direction of the electrical current in the heart comes from the sinoatrial node - as we mentioned before - to the bottom, and since the left ventricle is larger than the right ventricle - because it supplies the entire body with blood - so if we imagine the path of the current The electrical current in the heart will be from top to bottom and directed slightly to the left. This is what is called the heart axis.

• Any changes in this axis are called misalignment of the heart’s axis to the right or left

• ( Rt or Lt axial deviation)

• In the event of an infarction in the left ventricle... the electrical current directed towards the left decreases, and thus a misalignment of the heart's axis towards the right occurs.

• If there is hypertrophy in the left ventricle... the electrical current increases towards the left and thus an imbalance occurs in the heart’s axis towards the left.

• Cardiac axis imbalance can be measured through (QRS group) through only 3 images, namely (lead I, lead II, lead III), as (lead II) is located directly opposite the direction of the electrical current (opposite the direction of the heart axis). Directly, (lead I) is located to the left of (lead II), while (lead III) is to the right of (lead II).

• And based on the rule... we will find that the QRS group in (lead II) is represented by a large upward curvature because it is directly facing the electric current, while in (lead I, III) the curvature will also be upward, but less than (lead II), as they are not directly facing the electrical current.

• Thus, in the event of an imbalance in the heart’s axis to the right, the QRS group in (lead I) will be represented by a downward curvature, while in (lead III) its rate of curvature will increase upward... and vice versa!

Sixth: QT interval

• It starts from the beginning of (group QRS) until the end of (wave T), and it represents the time it takes for the ventricles to contract and relax.

It is equal to = 0.30 - 0.44 seconds, which is less than two large squares and one small square.

This distance increases due to antiarrhythmic drugs that block potassium channels.

Seventh: T wave

• Period: represents the period of diastole of the ventricles.

• Duration: 4 small squares represent height.

• Shape: It is very similar to wave B, but wave T is asymmetric and takes the shape of the letter T and is in an upright position in the image (lead II) and inverted in (aVR).

Diagnosing some differences due to changes in the T wave:

• The T wave is low or flat in cases of:

• Hypokalemia and pericardial effusion.

• It is equal to = 0.08 _ 0.12, i.e. (2-3) small squares.

Angina:

It is one of the most important distances that diagnose many cases, the most important of which are:

• The distance (AS_T) is lower than its normal level by 1 mm, and the (T wave) is also lower than its level... This is in addition to the presence of some types of heart rhythm disturbances

• If it is present in:

• 1. lead I, aVL) so this is a lateral infarction.

• 2. II,III, aVF) This is an inferior infarction.

• 3. V1-6) This is an anterior infarction.

• If the clot is old, it is characterized by the Q wave being 4 mm deeper than its level and 0.04 seconds wider. This is important for diagnosing an old clot.

• The EKG is one of the very important tests that medicine cannot do without or replace with another test... As we explained, it is very important in diagnosing many cases. It is important in diagnosing heart diseases resulting from high blood pressure, rheumatic fever, and birth defects. An ECG is often taken while the patient is lying in bed, as we talked about, and this method is called a resting ECG. This picture may be taken while the patient is exerting himself, and this test is called a stress electrocardiogram. It shows whether the heart is receiving enough oxygen during vigorous activity. Doctors use a stress EKG to diagnose coronary artery disease, in which the arteries supplying the heart muscle have narrowed to a dangerous extent, restricting blood flow.