Any change in the position of the heart is due to its rotation around three axes: anterior-posterior (sagittal), longitudinal (long) and transverse (horizontal). Magnitude and direction ECG waves the electrical positions of the heart are determined in various leads (Fig. 16).
Rice. 16. Diagram of the rotation of the heart around various axes. The arrows show the direction of rotation of the heart: a - around the anterior-posterior axis; b - around the long axis; c - around the transverse axis.
When the heart rotates around the anterior-posterior axis (Fig. 16, a), the heart takes either a horizontal or vertical position, which is most clearly reflected in standard leads. The horizontal position of the heart causes its electrical axis to deviate to the left, and the vertical position - to the right. The horizontal and vertical position of the heart is also reflected in unipolar leads from the limbs (see above).
The rotation of the heart along the long (longitudinal) axis (Fig. 16, b) occurs both clockwise and in the opposite direction and also causes ECG changes in all leads. Such a turn is observed during a number of physiological processes: a change in body position, the act of breathing, physical stress, etc.
When the heart rotates around the transverse (horizontal) axis, the apex of the heart shifts either anteriorly or posteriorly (Fig. 16, c). The rotation of the heart around the transverse axis is reflected in the unipolar limb leads.
Wilson proposed to determine the electrical position of the heart by the teeth of unipolar chest leads and limb leads. Electrocardiography distinguishes 5 positions of the heart: vertical, semi-vertical, intermediate, semi-horizontal and horizontal.
When the electrical position of the heart is vertical (angle a is +90°), the shape of the QRS complex in the unipolar lead from the left arm is similar to that observed in the right positions of the chest leads, and the shape of the QRS complex in the unipolar lead from the left leg is similar to that observed in the left positions of the chest leads ( Fig. 17).
Rice. 17. Electrocardiogram of a person with a healthy heart in standard chest and enlarged unipolar limb leads with a vertical position of the heart in the chest (the designations are the same as in Fig. 11): 1 - right ventricle; 2 - left ventricle.
In a semi-vertical position (angle α is +60°), the shape of the QRS complex in the unipolar lead from the left leg is similar to that observed in the left positions of the chest leads.
In an intermediate position of the heart (angle a is 4-30°), the shape of the QRS complex in the unipolar lead from the left arm and left leg is similar to that observed in the left positions of the chest leads.
With a semi-horizontal position of the heart (angle a is 0°), the shape of the QRS complex in the unipolar lead from the left arm is similar to that observed in the left positions of the chest leads.
When the heart is in a horizontal position (angle α is -30°), the shape of the QRS complex in the unipolar lead from the left arm is similar to that observed in the left positions of the chest leads, and the shape of the QRS complex in the unipolar lead from the left leg is similar to that observed in the right positions of the chest leads (Fig. . 18).
Rice. 18. Electrocardiogram of a person with a healthy heart in standard, chest and enlarged unipolar limb leads with a horizontal position of the heart (the designations are the same as in Fig. 11): 1 - right atrium; 2 - right ventricle; 3 - left ventricle.
In cases where there is no similarity between the unipolar chest leads and the unipolar limb leads, the electrical position of the heart is indeterminable. X-ray data have shown that the ECG does not always accurately reflect the position of the heart.
The ECG is usually recorded in a supine position.
Various positions of the subject (vertical, horizontal, on the right or left side), changing the position of the heart, cause changes in the ECG waves.
In a vertical position, the number of heart contractions increases, the electrical axis of the heart deviates to the right. This causes corresponding changes in the size and direction of ECG waves in standard and chest leads. The duration of the QRS complex decreases. The size of the T wave decreases, especially in leads II and III. The RS-T segment in these leads is slightly shifted downward.
When positioned on the right side, the electrical axis of the heart rotates around the long axis counterclockwise, and when positioned on the left side, it rotates clockwise with corresponding ECG changes.
The shape and direction of ECG waves in children differs from ECG of an adult person. IN old age P and T waves are often reduced. Duration P-Q interval and the QRS complex is usually upper limit norms. With age, deviation of the electrical axis of the heart to the left is much more common. The systolic reading is often slightly higher than expected.
In women, the amplitude of the P, T waves and the QRS complex is slightly smaller in the standard and precordial leads. More often there is a displacement of the RS-T segment and a negative T wave in lead III.
The area of the QRS complex waves is smaller. The ventricular gradient is smaller and deviated more to the left, the U wave is larger. The duration of the P-Q interval and QRS complex is on average shorter. The duration of electrical systole and systolic indicator are longer.
With a predominant effect on the heart of steam sympathetic division vegetative nervous system the number of heartbeats decreases. The P wave decreases and occasionally increases slightly. The duration of the P-Q interval increases slightly. The question of the influence of the parasympathetic department on the T wave cannot be considered completely clarified. According to some data, the T wave decreases, according to others, it increases. The Q-T segment often decreases.
With a predominant effect on the heart of the sympathetic department of the autonomic nervous system, the number of heart contractions increases. The P wave usually increases, sometimes decreases. The duration of the P-Q interval decreases. The T wave, according to some data, increases, according to others, it decreases.
Positive emotions have little effect on the ECG. Negative emotions (fear, fright, etc.) cause an increase in heart rate, mostly an increase, and sometimes a decrease in the waves.
During a deep breath, due to the downward displacement of the diaphragm, the heart assumes a vertical position. Its electrical axis deviates to the right, which causes corresponding changes in the ECG. Affects the shape of ECG waves and increases the impact on the heart during inhalation of the sympathetic department of the autonomic nervous system. During deep exhalation, ECG changes are caused by elevation of the diaphragm, deviation of the electrical axis of the heart to the left and the predominant effect on the heart of the parasympathetic division of the autonomic nervous system.
During normal breathing, these ECG changes are insignificant.
Physical stress can cause ECG changes in various ways: reflexively affect the depolarization and repolarization of the heart, reflexively and directly - on wiring system And contractile myocardium. Usually these paths are combined. ECG changes depend on the degree and duration of action of these factors.
Pronounced changes in ECG waves are observed after significant physical stress: an increase, and sometimes a mild broadening of the P wave; a decrease in the duration of the P-Q interval, and sometimes a downward shift due to layering of the P-Ta segment; a slight decrease in the duration of the QRS complex and often a deviation of the electrical axis of the heart to the right, as well as a downward shift of the RS-T segment; enlargement of the T wave; decrease segment Q-T proportional to the increase in heart rate; the appearance of an enlarged U wave.
Eating a large amount of food causes an increase in heart rate and a decrease in the T wave (occasionally significant, even becoming negative) in leads II and III. Sometimes there is a slight increase in the P wave, an increase in the Q-T segment and systolic indicator.
These ECG changes reach a maximum after 30-60 minutes. after eating and disappear after 2 hours.
ECG changes during the day in healthy people are insignificant and relate mainly to the T wave. The T wave reaches its maximum value early in the morning, and after breakfast its value is the smallest.
The electrical axis of the heart is the average direction of the electromotive force of the heart during the entire period of depolarization. There are:
· normal position of the electrical axis of the heart: angle α is +30- +70°;
horizontal position of the electrical axis of the heart: angle α is 0- +30°:
Deviation of the electrical axis of the heart to the left: angle α is −30-0°;
A sharp deviation of the electrical axis of the heart to the left: the α angle is less than −30° (see “Block of the anterior branch of the left bundle branch”);
· vertical position of the electrical axis of the heart: angle α is +70- +90°:
Deviation of the electrical axis of the heart to the right: angle α is +90- +120°;
A sharp deviation of the electrical axis of the heart to the right: the angle α is more than +120° (see "Blockade posterior branch left bundle branch").
ECG 5. Normal position of the electrical axis of the heart
10 mm/mV 50 mm/s
Heart rate = 58/min. Email axis 41° is normal. P−Q= 0.176 s. P= 0.081 s. QRS= 0.075 s. Q−T= 0.370 s. Sinus rhythm, bradycardia. The voltage is satisfactory. Normal position of the electrical axis of the heart. Early repolarization syndrome.
ECG 6. Horizontal position of the electrical axis of the heart
10 mm/mV 50 mm/s
Heart rate = 57/min. Email 10° axis is horizontal. P−Q= 0.120 s. P= 0.084 s. QRS= 0.078 s. Q−T= 0.384 s. Sinus rhythm, bradycardia. The voltage is satisfactory. Horizontal position of the electrical axis of the heart.
ECG 7. Deviation of the electrical axis of the heart to the left
10 mm/mV 50 mm/s
Heart rate = 60/min. Email axis -21°- off Left. P−Q= 0.172 s. P= 0.083 s. QRS= 0.074 s. Q−T= 0.380 s. Sinus rhythm. The voltage is satisfactory. Deviation of the electrical axis of the heart to the left.
ECG 8. Vertical position of the electrical axis of the heart
10 mm/mV 50 mm/s
Heart rate = 67-87 per minute. Email 84° axis is vertical. P−Q= 0.120 s. P= 0.085 s. QRS= 0.076 s. Q−T= 0.346 s. Sinus arrhythmia. The voltage is satisfactory. Vertical position of the electrical axis of the heart.
ECG 9. Deviation of the electrical axis of the heart to the right
10 mm/mV 50 mm/s
Heart rate = 78/min. Email axis 98° - off Right. P−Q= 0.148 s. P= 0.092 s. QRS= 0.089 s. Q−T= 0.357 s. Sinus rhythm. The voltage is satisfactory. Deviation of the electrical axis of the heart to the right. Signs of right ventricular hypertrophy.
Rotations of the heart around the longitudinal axis
Turns the heart around longitudinal axis, conventionally drawn through the apex and base of the heart, are determined by the configuration of the complex QRS in the chest leads, the axes of which are located in the horizontal plane. To do this, you usually need to set the localization transition zone, and also evaluate the shape of the complex QRS in lead V 6.
In the normal position of the heart in the horizontal plane, the transition zone is most often located in lead V 3. In this lead, waves of equal amplitude are recorded R And S. In lead V 6, the ventricular complex usually has the shape q R or q Rs.
When the heart rotates around the longitudinal axis clockwise (if you follow the rotation of the heart from below, from the apex), the transition zone shifts slightly to the left, into the region of lead V 4 -V 5, and in lead V 6 the complex takes the form Rs.
When the heart rotates around its longitudinal axis counterclockwise, the transition zone may shift to the right, to lead V2. In leads V 5, V 6, a deepened (but not pathological) tooth is recorded Q, and the complex QRS takes the form q R.
It is important to know! Rotations of the heart around the longitudinal axis clockwise are often combined with vertical position electrical axis of the heart or deviation of the heart axis to the right, and counterclockwise turns - with a horizontal position or deviation of the electrical axis to the left.
Rotations of the heart around the transverse axis
Rotations of the heart around the transverse axis are usually associated with deviation of the apex of the heart forward or backward relative to its normal position. When the heart rotates around the transverse axis with the apex forward, the ventricular complex QRS in standard leads takes the form qRI, qRII, q RIII. When the heart rotates around the transverse axis with its apex backwards, the ventricular complex in standard leads has the shape RSI, RSII, RSIII.
ECG 10. Turning the heart clockwise
10 mm/mV 50 mm/s
Heart rate = 90/min. Email 90° axis is vertical. P−Q= 0.160 s. P= 0.096 s. QRS= 0.069 s. Q−T= 0.300 s. Sinus rhythm, tachycardia. The voltage is satisfactory. Vertical position of the electrical axis of the heart. Rotate the heart clockwise (right ventricle forward).
ECG 11. Turning the heart counterclockwise
10 mm/mV 50 mm/s
When the heart rotates around its longitudinal axis clockwise (as viewed from the apex), the right ventricle moves forward and upward, and the left- back and down. This position is a variant of the vertical position of the heart axis. In this case, a deep Q wave appears on the ECG in lead III, and occasionally in lead aVF, which can simulate signs of focal changes in the posterior phrenic region of the left ventricle.
At the same time, a pronounced S wave is detected in leads I and aVL (the so-called Q III S I syndrome). There is no q wave in leads I, V 5 and V 6. The transition zone may shift to the left. These changes also occur with acute and chronic enlargement of the right ventricle, which requires appropriate differential diagnosis.
The figure shows an ECG healthy woman 35 years asthenic build. There are no complaints about dysfunction of the heart and lungs. There is no history of diseases that could cause hypertrophy of the right heart. With physical and x-ray examination pathological changes no heart or lungs were identified.
The ECG shows the vertical position of the atrial and ventricular vectors. Â P = +75°. Â QRS = +80°. Noteworthy are the pronounced q waves along with tall R waves in leads II, III and aVF, as well as S waves in leads I and aVL. Transition zone in V 4 -V 5. These ECG features could provide grounds for determining hypertrophy of the right heart, but the absence of complaints, anamnesis data, results of clinical and X-ray studies made it possible to exclude this assumption and consider the ECG to be a normal variant.
The rotation of the heart around the longitudinal axis counterclockwise (i.e., with the left ventricle forward and upward), as a rule, is combined with a deviation of the apex to the left and is quite a rare option horizontal position of the heart. This variant is characterized by a pronounced Q wave in leads I, aVL and left chest along with pronounced S waves in leads III and aVF. Deep Q waves may mimic signs of focal changes in the lateral or anterior wall of the left ventricle. The transition zone with this option is usually shifted to the right.
A typical example of this variant of the norm is the ECG shown in the figure of a 50-year-old patient with a diagnosis of: chronic gastritis. This curve shows a pronounced Q wave in leads I and aVL and a deep S wave in lead III.
“Practical electrocardiography”, V.L. Doshchitsin
In some cases, options normal ECG, Related different position axis of the heart are mistakenly interpreted as a manifestation of one or another pathology. In this regard, we will first consider the “positional” variants of a normal ECG. As mentioned above, healthy people may have a normal, horizontal or vertical position of the electrical axis of the heart, which depends on body type, age and...
A normal ECG with a horizontal position of the electrical axis of the heart must be distinguished from signs of left ventricular hypertrophy. When the electrical axis of the heart is vertical, the R wave has a maximum amplitude in leads aVF, II and III; in leads aVL and I, a pronounced S wave is recorded, which is also possible in the left chest leads. ÂQRS = + 70° - +90°. Such...
Posterior rotation of the heart is accompanied by the appearance of a deep S1 wave in leads I, II and III, as well as in lead aVF. A pronounced S wave may also be observed in all chest leads with a shift of the transition zone to the left. This variant of a normal ECG requires differential diagnosis with one of the ECG variants for right ventricular hypertrophy (S-type). The picture shows...
Heart rotation around its longitudinal axis, drawn through the base and apex of the heart, according to Grant, does not exceed 30°. This rotation is viewed from the apex of the heart. The initial (Q) and final (S) vectors are projected onto the negative half of the lead V axis, therefore the QRSV6 complex has the shape of qRs (the main part of the QRS loop k + V6). The QRS complex has the same shape in leads I, II, III.
Turn of the heart clockwise corresponds to the position of the right ventricle somewhat more anteriorly, and the left ventricle somewhat more posteriorly, than the normal position of these chambers of the heart. In this case, the interventricular septum is located almost parallel to the frontal plane, and the initial QRS vector, reflecting the electromotive force (EMF) of the interventricular septum, is oriented almost perpendicular to the frontal plane and to the axes of leads I, V5 and V6. It also tilts slightly up and to the left. Thus, when the heart is rotated clockwise around the longitudinal axis, the RS complex is recorded in all chest leads, and the RSI and QRIII complexes are recorded in standard leads.
ECG healthy man M, 34 years old. The rhythm is sinus, regular; heart rate - 78 per 1 min. (R-R = 0.77ceK.). Interval P - Q = 0.14 sec. Р=0.09 sec., QRS=0.07 sec. (QIII=0.025 sec.), d -T= 0.34 sec. RIII>RII>RI>SOI. AQRS=+76°. AT=+20°. AP=+43°. ZQRS - T = 56°. The wave PI-III, V2-V6, aVL, aVF is positive, not higher than 2 mm (lead II). The PV1 wave is biphasic (+-) with a larger positive phase. Complex QRSr type RS, QRSIII type QR (Q pronounced, but not extended). Complex QRSV| _„ type rS. QRSV4V6 type RS or Rs. Transition zone of the QRS complex in lead V4 (normal). The RS segment - TV1 _ V3 is shifted upward by no more than 1 mm; in the remaining leads it is at the level of the isoelectric line.
TI wave is negative, shallow. The TaVF wave is positive. TV1 is smoothed. TV2-V6 is positive, low and increases slightly towards leads V3, V4.
Vector analysis. The absence of QIV6 (type RSI, V6) indicates the orientation of the initial QRS vector forward and to the left. This orientation may be associated with the location of the interventricular septum parallel to chest wall, which is observed when the heart is rotated clockwise around its longitudinal axis. The normal location of the QRS transition zone shows that in this case the hourly turn is one of the options for a normal ECG. A weakly negative TIII wave with a positive TaVF can also be regarded as normal.
Conclusion. Variant of a normal ECG. Vertical position of the electrical axis of the heart with clockwise rotation around the longitudinal axis.
Interventricular septum at the same time almost perpendicular to the frontal plane. The initial QRS vector is oriented to the right and slightly downward, which determines the presence of a pronounced QI, V5V6 wave. In these leads there is no S wave (QRI, V5, V6 shape, since the base of the ventricles occupies a more posterior left position and the final vector is oriented back and to the left.
ECG of a healthy woman Z., 36 years old. Sinus (respiratory) arrhythmia. The number of contractions is 60 - 75 per minute. P-Q interval=0.12 sec. P=0.08 sec. QRS=0.07 sec. Q-T=0.35 sec. R,>R1>R1II. AQRS=+44°. At=+30°. QRS angle - T=14°. Ar = +56°. Complex QRS1,V5,V6 type qR. QRSIII type rR"s. The RV1 tooth is slightly enlarged (6.5 mm), but RV1
Other teeth and ECG segments without abnormalities. Rp wave (1.8 mm)>P1>Ppg Vector P is directed downward, to the left along the axis of lead II. The average vector in the horizontal plane (chest leads) is parallel to the axis of lead V4 (highest R in lead V4). TIII is smoothed, TaVF is positive.
Conclusion. A variant of a normal ECG (rotation of the heart around the longitudinal axis counterclockwise).
In the ECG analysis protocol information about rotations around the longitudinal (as well as transverse) axis of the heart along ECG data noted in the description. It is not advisable to include them in the ECG conclusion, since they either constitute a variant of the norm, or are a symptom of ventricular hypertrophy, which should be written about in the conclusion.
Electrical axis of the heart (ECA) is a term used in cardiology and functional diagnostics, reflecting the electrical processes occurring in the heart.
The direction of the electrical axis of the heart shows the total magnitude of bioelectric changes occurring in the heart muscle with each contraction. The heart is a three-dimensional organ, and in order to calculate the direction of the EOS, cardiologists represent the chest as a coordinate system.
Each electrode, when removed, registers bioelectrical excitation occurring in a certain area of the myocardium. If you project the electrodes onto a conventional coordinate system, you can also calculate the angle of the electrical axis, which will be located where the electrical processes are strongest.
Conducting system of the heart and why is it important for determining EOS?
The conduction system of the heart consists of sections of the heart muscle consisting of so-called atypical muscle fibers. These fibers are well innervated and provide synchronous contraction of the organ.
Myocardial contraction begins with the appearance of an electrical impulse in the sinus node (which is why correct rhythm healthy heart called sinus). From the sinus node, the electrical impulse travels to the atrioventricular node and further along the His bundle. This bundle passes through the interventricular septum, where it divides into the right, heading towards the right ventricle, and the left legs. The left bundle branch is divided into two branches, anterior and posterior. The anterior branch is located in the anterior sections of the interventricular septum, in the anterolateral wall of the left ventricle. The posterior branch of the left bundle branch is located in the middle and lower third of the interventricular septum, posterolateral and bottom wall left ventricle. We can say that the posterior branch is located slightly to the left of the anterior one.
The myocardial conduction system is a powerful source of electrical impulses, which means that electrical changes occur in it first in the heart, preceding heart rate. If there are disturbances in this system, the electrical axis of the heart can significantly change its position, which will be discussed below.
Variants of the position of the electrical axis of the heart in healthy people
The mass of the cardiac muscle of the left ventricle is normally much greater than the mass of the right ventricle. Thus, the electrical processes occurring in the left ventricle are overall stronger, and EOS will be directed specifically at it. If we project the position of the heart on the coordinate system, the left ventricle will be in the area +30 + 70 degrees. This is what will happen normal position axes. However, depending on individual anatomical features and physique the position of the EOS in healthy people ranges from 0 to +90 degrees:
- So, vertical position EOS will be considered in the range from + 70 to +90 degrees. This position of the heart axis occurs in tall, skinny people– asthenics.
- Horizontal position of the EOS more common in short, stocky people with a wide chest– hypersthenics, and its value ranges from 0 to + 30 degrees.
The structural features for each person are very individual; there are practically no pure asthenics or hypersthenics; more often they are intermediate body types, therefore the electrical axis can have an intermediate value (semi-horizontal and semi-vertical).
All five position options (normal, horizontal, semi-horizontal, vertical and semi-vertical) occur in healthy people and are not pathological.
So, in conclusion, the ECG is absolutely healthy person it can be said: “EOS is vertical, sinus rhythm, heart rate – 78 per minute,” which is a variant of the norm.
Rotations of the heart around the longitudinal axis help determine the position of the organ in space and, in some cases, are an additional parameter in diagnosing diseases.
The definition of “rotation of the electrical axis of the heart around an axis” may well be found in descriptions of electrocardiograms and is not something dangerous.
When can the position of the EOS indicate heart disease?
The position of the EOS itself is not a diagnosis. However There are a number of diseases in which there is a displacement of the heart axis. Significant changes in the position of the EOS result from:
- of various origins (especially dilated cardiomyopathy).
EOS deviations to the left
Thus, deviation of the electrical axis of the heart to the left may indicate (LVH), i.e. an increase in size, which is also not an independent disease, but may indicate an overload of the left ventricle. This condition often occurs with a long-term current and is associated with significant vascular resistance to blood flow, as a result of which the left ventricle must contract with greater force, the mass of the ventricular muscles increases, which leads to its hypertrophy. Ischemic disease, chronic heart failure, and cardiomyopathies also cause left ventricular hypertrophy.
hypertrophic changes in the myocardium of the left ventricle are the most common cause of deviation of the EOS to the left
In addition, LVH develops when the valve apparatus of the left ventricle is damaged. This condition is caused by stenosis of the aortic mouth, in which the ejection of blood from the left ventricle is difficult, insufficiency aortic valve, when some of the blood returns to the left ventricle, overloading it with volume.
These defects can be either congenital or acquired. The most often acquired heart defects are a consequence of previous history. Left ventricular hypertrophy is found in professional athletes. In this case, a consultation with a highly qualified sports doctor is necessary to decide on the possibility of continuing to play sports.
Also, the EOS can be deviated to the left at and different . Deviation el. the axis of the heart to the left, together with a number of other ECG signs, is one of the indicators of blockade of the anterior branch of the left bundle branch.
EOS deviations to the right
A shift in the electrical axis of the heart to the right may indicate right ventricular hypertrophy (RVH). Blood from the right ventricle enters the lungs, where it is enriched with oxygen. Chronic diseases respiratory organs, accompanied by, such as bronchial asthma, chronic obstructive disease in the lungs over a long period of time cause hypertrophy. Stenosis leads to right ventricular hypertrophy pulmonary artery and tricuspid valve insufficiency. As in the case of the left ventricle, RVH is caused by coronary disease heart disease, chronic heart failure and cardiomyopathies. Deviation of the EOS to the right occurs with complete blockade of the posterior branch of the left bundle branch.
What to do if EOS displacement is found on the cardiogram?
None of the above diagnoses can be made on the basis of EOS displacement alone. The position of the axis serves only as an additional indicator in diagnosing a particular disease. When the heart axis is deviated beyond the limits normal values(from 0 to +90 degrees), consultation with a cardiologist and a number of studies are required.
But still the main cause of EOS displacement is myocardial hypertrophy. The diagnosis of hypertrophy of a particular part of the heart can be made based on the results. Any disease leading to a displacement of the heart axis is accompanied by a number of clinical signs and demands additional examination. The situation should be alarming when, with a pre-existing position of the EOS, its sharp deviation on the ECG occurs. In this case, the deviation most likely indicates the occurrence of a blockade.
The displacement of the electrical axis of the heart itself does not require treatment, refers to electrocardiological signs and requires, first of all, to determine the cause of its occurrence. Only a cardiologist can determine the need for treatment.
Video: EOS in the course “Everyone can do an ECG”
