The s wave on the ecg reflects. S wave ECG
For an error-free interpretation of changes in the analysis of the ECG, it is necessary to adhere to the scheme for its interpretation given below.
General scheme for decoding an ECG: decoding a cardiogram in children and adults: general principles, reading the results, an example of decoding.
Normal electrocardiogram
Any ECG consists of several teeth, segments and intervals, reflecting the complex process of propagation of the excitation wave through the heart.
The shape of the electrocardiographic complexes and the size of the teeth are different in different leads and are determined by the magnitude and direction of the projection of the moment vectors of the EMF of the heart on the axis of one or another lead. If the projection of the torque vector is directed towards the positive electrode of this lead, an upward deviation from the isoline is recorded on the ECG - positive teeth. If the projection of the vector is directed towards the negative electrode, the deviation downward from the isoline is recorded on the ECG - negative teeth. In the case when the moment vector is perpendicular to the lead axis, its projection on this axis is zero and no deviations from the isoline are recorded on the ECG. If, during the cycle of excitation, the vector changes its direction with respect to the poles of the lead axis, then the tooth becomes biphasic.
Normal ECG segments and teeth.
Prong R.
The P wave reflects the process of depolarization of the right and left atria. In a healthy person, in leads I, II, aVF, V-V, the P wave is always positive, in leads III and aVL, V it can be positive, biphasic or (rarely) negative, and in lead aVR the P wave is always negative. In leads I and II, the P wave has a maximum amplitude. The duration of the P wave does not exceed 0.1 s, and its amplitude is 1.5-2.5 mm.
P-Q (R) interval.
The P-Q (R) interval reflects the duration of the atrioventricular conduction, i.e. the time of propagation of excitation through the atria, AV node, His bundle and its branches. Its duration is 0.12-0.20 s and in a healthy person depends mainly on the heart rate: the higher the heart rate, the shorter the P-Q (R) interval.
Ventricular QRST complex.
The ventricular QRST complex reflects the complex process of propagation (QRS complex) and extinction (RS segment - T and T wave) of excitation along the ventricular myocardium.
Q wave.
The Q wave can normally be recorded in all standard and enhanced unipolar leads from the limbs and in the chest leads V-V. The amplitude of the normal Q wave in all leads, except for aVR, does not exceed the height of the R wave, and its duration is 0.03 s. In lead aVR, a healthy person can have a deep and wide Q wave or even a QS complex.
R wave.
Normally, the R wave can be recorded in all standard and enhanced limb leads. In lead aVR, the R wave is often poorly expressed or absent altogether. In the chest leads, the amplitude of the R wave gradually increases from V to V, and then decreases slightly in V and V. Sometimes the r wave may be absent. Barb
R reflects the spread of excitation along the interventricular septum, and the R wave - along the muscle of the left and right ventricles. The interval of internal deviation in lead V does not exceed 0.03 s, and in lead V - 0.05 s.
S wave.
In a healthy person, the amplitude of the S wave in various electrocardiographic leads fluctuates within wide limits, not exceeding 20 mm. In the normal position of the heart in the chest in the leads from the limbs, the S amplitude is small, except for lead aVR. In the chest leads, the S wave gradually decreases from V, V to V, and in leads V, V it has little or no amplitude. Equality of R and S waves in the chest leads ("transition zone") is usually recorded in lead V or (less often) between V and V or V and V.
The maximum duration of the ventricular complex does not exceed 0.10 s (more often 0.07-0.09 s).
Segment RS-T.
The RS-T segment in a healthy person in the limb leads is located on the isoline (0.5 mm). Normally, in the chest leads V-V, there may be a slight displacement of the RS-T segment upward from the isoline (no more than 2 mm), and in leads V - downward (no more than 0.5 mm).
T wave
Normally, the T wave is always positive in leads I, II, aVF, V-V, with T\u003e T and T\u003e T. In leads III, aVL and V, the T wave can be positive, biphasic, or negative. In lead aVR, the T wave is normally always negative.
Q-T interval (QRST)
The Q-T interval is called electrical ventricular systole. Its duration depends primarily on the number of heartbeats: the higher the heart rate, the shorter the proper Q-T interval. The normal duration of the Q-T interval is determined by the Bazett formula: Q-T \u003d K, where K is a coefficient equal to 0.37 for men and 0.40 for women; R-R is the duration of one cardiac cycle.
Analysis of the electrocardiogram.
The analysis of any ECG should begin with checking the correctness of the technique for its registration. First, you need to pay attention to the presence of a variety of interference. Interference arising from ECG registration:
a - overflow currents - network pickup in the form of regular oscillations with a frequency of 50 Hz;
b - “swimming” (drift) of the isoline as a result of poor contact of the electrode with the skin;
c - pickup caused by muscle tremor (irregular frequent fluctuations are visible).
Interference arising from ECG registration
Secondly, it is necessary to check the amplitude of the reference millivolt, which should correspond to 10mm.
Third, the paper speed should be assessed during ECG recording. When recording an ECG at a speed of 50mm with 1mm on a paper tape, it corresponds to a time interval of 0.02s, 5mm - 0.1s, 10mm - 0.2s, 50mm - 1.0s.
I. Analysis of heart rate and conduction:
1) assessment of the regularity of heart contractions;
2) counting the number of heartbeats;
3) determination of the source of excitation;
4) evaluation of the conductivity function.
II. Determination of turns of the heart around the anteroposterior, longitudinal and transverse axes:
1) determining the position of the electrical axis of the heart in the frontal plane;
2) determination of rotations of the heart around the longitudinal axis;
3) determination of turns of the heart around the transverse axis.
III. Analysis of the atrial R.
IV. Ventricular QRST Analysis:
1) analysis of the QRS complex,
2) analysis of the RS-T segment,
3) analysis of the Q-T interval.
V. Electrocardiographic conclusion.
I.1) The regularity of the heartbeats is assessed by comparing the duration of the R-R intervals between successively recorded heart cycles. The R-R interval is usually measured between the tops of the R waves. Regular, or correct, heart rhythm is diagnosed if the duration of the measured R-R is the same and the spread of the values \u200b\u200bobtained does not exceed 10% of the average R-R duration. In other cases, the rhythm is considered abnormal (irregular), which can be observed with extrasystole, atrial fibrillation, sinus arrhythmia, etc.
2) With the correct rhythm, the heart rate (HR) is determined by the formula: HR \u003d.
With an irregular rhythm, an ECG in one of the leads (most often in standard lead II) is recorded longer than usual, for example, within 3-4 s. Then the number of QRS complexes recorded in 3 s is counted, and the result is multiplied by 20.
In a healthy person at rest, the heart rate is from 60 to 90 per minute. An increase in heart rate is called tachycardia, and a decrease in heart rate is called bradycardia.
Assessment of regularity of rhythm and heart rate:
a) correct rhythm; b) c) wrong rhythm
3) To determine the source of excitation (pacemaker), it was necessary to assess the course of excitation in the atria and establish the ratio of the R waves to the ventricular QRS complexes.
Sinus rhythmcharacterized by: the presence in the II standard lead of positive H waves preceding each QRS complex; constant identical shape of all P waves in the same lead.
In the absence of these signs, various variants of non-sinus rhythm are diagnosed.
Atrial rhythm(from the lower atria) is characterized by the presence of negative P, P waves and unchanged QRS complexes following them.
The rhythm from the AV connectioncharacterized by: the absence of a P wave on the ECG, merging with the usual unchanged QRS complex, or the presence of negative P waves located after the usual unchanged QRS complexes.
Ventricular (idioventricular) rhythmcharacterized by: a slow ventricular rate (less than 40 beats per minute); the presence of expanded and deformed QRS complexes; the absence of a natural connection between the QRS complexes and the P waves.
4) For a rough preliminary assessment of the conduction function, it is necessary to measure the duration of the P wave, the duration of the P-Q (R) interval and the total duration of the ventricular QRS complex. An increase in the duration of these teeth and intervals indicates a slowdown in conduction in the corresponding section of the cardiac conduction system.
II. Determination of the position of the electrical axis of the heart. There are the following options for the position of the electrical axis of the heart:
Bailey's six-axis system.
and) Determination of the angle by graphic method.Calculate the algebraic sum of the amplitudes of the QRS complex teeth in two leads from the limbs (usually I and III standard leads are used), the axes of which are located in the frontal plane. The positive or negative value of the algebraic sum in an arbitrarily chosen scale is plotted on the positive or negative part of the axis of the corresponding lead in the six-axis Bailey coordinate system. These values \u200b\u200brepresent the projections of the desired electrical axis of the heart on the axis I and III of the standard leads. From the ends of these projections, the perpendiculars to the lead axes are restored. The intersection point of the perpendiculars is connected to the center of the system. This line is the electrical axis of the heart.
b) Visual definition of the angle.Allows you to quickly estimate the angle with an accuracy of 10 °. The method is based on two principles:
1. The maximum positive value of the algebraic sum of the teeth of the QRS complex is observed in that lead, the axis of which approximately coincides with the location of the electrical axis of the heart, parallel to it.
2. A complex of the RS type, where the algebraic sum of the teeth is equal to zero (R \u003d S or R \u003d Q + S), is recorded in the lead whose axis is perpendicular to the electrical axis of the heart.
In the normal position of the electrical axis of the heart: RRR; in leads III and aVL, the R and S waves are approximately equal to each other.
With a horizontal position or deviation of the electrical axis of the heart to the left: high R waves are fixed in leads I and aVL, with R\u003e R\u003e R; a deep S wave is recorded in lead III.
With an upright position or deviation of the electrical axis of the heart to the right: high R waves are recorded in leads III and aVF, and R R\u003e R; deep S waves are recorded in leads I and aV
III. P wave analysisincludes: 1) measurement of the amplitude of the P wave; 2) measuring the duration of the P wave; 3) determination of the polarity of the P wave; 4) determining the shape of the P wave.
IV.1) Analysis of the QRS complexincludes: a) Q wave assessment: amplitude and comparison with R amplitude, duration; b) evaluation of the R wave: amplitude, comparing it with the amplitude of Q or S in the same lead and with R in other leads; the duration of the interval of internal deviation in leads V and V; possible splitting of a tooth or the appearance of an additional one; c) evaluation of the S wave: amplitude, comparing it with the amplitude R; possible widening, jagging or splitting of the tooth.
2) Whenanalysis of the RS-T segmentit is necessary: \u200b\u200bfind the junction point j; measure its deviation (+ -) from the isoline; measure the magnitude of the displacement of the RS-T segment of the isoline up or down at a point located from point j to the right by 0.05-0.08 s; determine the form of a possible displacement of the RS-T segment: horizontal, oblique, oblique.
3) When analyzing the T wave should: determine the polarity of T, evaluate its shape, measure the amplitude.
4) Q-T interval analysis: measuring duration.
V. Electrocardiographic conclusion:
1) the source of the heart rhythm;
2) the regularity of the heart rhythm;
4) the position of the electrical axis of the heart;
5) the presence of four electrocardiographic syndromes: a) cardiac arrhythmias; b) conduction disturbances; c) hypertrophy of the myocardium of the ventricles and atria or their acute overload; d) myocardial damage (ischemia, degeneration, necrosis, scarring).
Electrocardiogram for cardiac arrhythmias
1. Violations of the automatism of the CA-node (nomotopic arrhythmias)
1) Sinus tachycardia: an increase in the number of heartbeats up to 90-160 (180) per minute (shortening of the R-R intervals); maintaining the correct sinus rhythm (correct alternation of the P wave and the QRST complex in all cycles and a positive P wave).
2) Sinus bradycardia: a decrease in the number of heartbeats to 59-40 per minute (an increase in the duration of the R-R intervals); maintaining the correct sinus rhythm.
3) Sinus arrhythmia: fluctuations in the duration of the R-R intervals, exceeding 0.15 s and associated with the phases of breathing; preservation of all electrocardiographic signs of sinus rhythm (alternation of the P wave and the QRS-T complex).
4) Syndrome of weakness of the sinoatrial node:persistent sinus bradycardia; periodic appearance of ectopic (non-sinus) rhythms; the presence of a SA blockade; bradycardia-tachycardia syndrome.
a) ECG of a healthy person; b) sinus bradycardia; c) sinus arrhythmia
2. Extrasystole.
1) Atrial premature beats: premature extraordinary appearance of the P 'wave and the following QRST' complex; deformation or change in the polarity of the P 'wave of the extrasystole; the presence of an unchanged extrasystolic ventricular complex QRST ′, similar in shape to ordinary normal complexes; the presence of an incomplete compensatory pause after an atrial extrasystole.
Atrial premature beats (II standard lead): a) from the upper atria; b) from the middle sections of the atria; c) from the lower parts of the atria; d) blocked atrial premature beats.
2) Extrasystoles from the atrioventricular junction: premature extraordinary appearance on the ECG of the unchanged ventricular QRS complex, similar in shape to the other QRST complexes of sinus origin; negative P 'wave in leads II, III and aVF after extrasystolic QRS' complex or absence of P 'wave (fusion of P' and QRS '); the presence of an incomplete compensatory pause.
3) Ventricular extrasystole: premature extraordinary appearance on the ECG of the altered ventricular QRS complex; significant expansion and deformation of the extrasystolic QRS 'complex; the location of the RS-T ′ segment and the T ′ tooth of the extrasystole is discordant to the direction of the main tooth of the QRS ′ complex; the absence of a P wave before the ventricular extrasystole; the presence in most cases after a ventricular extrasystole of a full compensatory pause.
a) left ventricular; b) right ventricular extrasystole
3. Paroxysmal tachycardia.
1) Atrial paroxysmal tachycardia: a sudden onset and also suddenly ending attack of increased heart rate up to 140-250 per minute while maintaining the correct rhythm; the presence of a reduced, deformed, biphasic or negative P wave in front of each ventricular QRS complex; normal unchanged ventricular QRS complexes; in some cases, there is a deterioration in atrioventricular conduction with the development of I degree atrioventricular block with periodic drops of individual QRS complexes (intermittent signs).
2) Paroxysmal tachycardia from the atrioventricular junction:a sudden onset and also suddenly ending attack of increased heart rate up to 140-220 per minute while maintaining the correct rhythm; the presence in leads II, III and aVF of negative P 'waves located behind the QRS' complexes or merging with them and not recorded on the ECG; normal unchanged ventricular QRS complexes'.
3) Ventricular paroxysmal tachycardia: a sudden onset and also suddenly ending attack of increased heart rate up to 140-220 per minute, while maintaining the correct rhythm in most cases; deformation and expansion of the QRS complex for more than 0.12 s with discordant location of the RS-T segment and the T wave; the presence of atrioventricular dissociation, i.e. complete separation of the frequent ventricular rhythm and normal atrial rhythm with occasionally recorded single normal unchanged QRST complexes of sinus origin.
4. Atrial flutter: the presence on the ECG of frequent - up to 200-400 per minute - regular, similar to each other atrial F waves with a characteristic sawtooth shape (leads II, III, aVF, V, V); in most cases, correct, regular ventricular rhythm at regular F-F intervals; the presence of normal unchanged ventricular complexes, each of which is preceded by a certain number of atrial F waves (2: 1, 3: 1, 4: 1, etc.).
5. Flicker (fibrillation) of the atria: absence in all leads of the P wave; presence throughout the entire cardiac cycle of irregular waves fhaving different shapes and amplitudes; waves fbetter recorded in leads V, V, II, III and aVF; irregularity of ventricular QRS complexes - irregular ventricular rhythm; the presence of QRS complexes, which in most cases have a normal unchanged appearance.
a) large-wavy form; b) fine-wavy form.
6. Ventricular flutter:frequent (up to 200-300 per minute), regular and equal in shape and amplitude, flutter waves resembling a sinusoidal curve.
7. Flicker (fibrillation) of the ventricles:frequent (from 200 to 500 per minute), but irregular waves, differing from each other in different shapes and amplitudes.
Electrocardiogram for violations of the conduction function.
1. Sinoatrial blockade:periodic loss of individual cardiac cycles; an increase at the time of loss of cardiac cycles of the pause between two adjacent P or R waves by almost 2 times (less often 3 or 4 times) compared with the usual intervals of P-P or R-R.
2. Intra-atrial block:an increase in the duration of the P wave by more than 0.11 s; cleavage of the P wave.
3. Atrioventricular blockade.
1) I degree:increase in the duration of the interval P-Q (R) more than 0.20 s.
a) atrial form: expansion and cleavage of the P wave; QRS of normal form.
b) nodular form: lengthening of the P-Q (R) segment.
c) distal (three-beam) form: pronounced deformation of the QRS.
2) II degree:prolapse of individual ventricular QRST complexes.
a) Mobitz type I: gradual lengthening of the P-Q (R) interval with subsequent loss of QRST. After an extended pause - again a normal or slightly lengthened P-Q (R), after which the whole cycle is repeated.
b) Mobitz type II: QRST prolapse is not accompanied by a gradual lengthening of P-Q (R), which remains constant.
c) Mobitz type III (incomplete AV block): either every second (2: 1), or two or more ventricular complexes in a row (block 3: 1, 4: 1, etc.).
3) III degree:complete separation of the atrial and ventricular rhythms and a decrease in the number of ventricular contractions to 60-30 per minute or less.
4. Blockade of the legs and branches of the His bundle.
1) Blockade of the right leg (branch) of the His bundle.
a) Complete blockade: the presence in the right chest leads V (less often in leads from the extremities III and aVF) of the QRS complexes of the rSR ′ or rSR ′ type, having an M-shaped appearance, and R ′\u003e r; the presence of a widened, often serrated S wave in the left chest leads (V, V) and leads I, aVL; an increase in the duration (width) of the QRS complex more than 0.12 s; the presence in lead V (less often in III) of depression of the RS-T segment with a convexity facing upward, and a negative or biphasic (- +) asymmetric T wave.
b) Incomplete blockade: the presence of a QRS complex of the rSr 'or rSR' type in lead V, and a slightly widened S wave in leads I and V; the duration of the QRS complex is 0.09-0.11 s.
2) Blockade of the left anterior branch of the His bundle:a sharp deviation of the electrical axis of the heart to the left (angle α –30 °); QRS in leads I, aVL type qR, III, aVF, type II rS; the total duration of the QRS complex is 0.08-0.11 s.
3) Blockade of the left posterior branch of the His bundle:a sharp deviation of the electrical axis of the heart to the right (angle α120 °); the form of the QRS complex in leads I and aVL of type rS, and in leads III, aVF - of type qR; the duration of the QRS complex is within 0.08-0.11 sec.
4) Left bundle branch block: in leads V, V, I, aVL, the broadened deformed ventricular complexes of the R type with a split or wide apex; in leads V, V, III, aVF, broadened deformed ventricular complexes that look like QS or rS with a split or wide apex of the S wave; increase in the total duration of the QRS complex more than 0.12 s; the presence in leads V, V, I, aVL discordant in relation to QRS displacement of the RS-T segment and negative or biphasic (- +) asymmetric T waves; deviation of the electrical axis of the heart to the left is often observed, but not always.
5) Blockade of three branches of the His bundle:atrioventricular block I, II or III degree; blockade of two branches of the bundle of His.
Electrocardiogram for atrial and ventricular hypertrophy.
1. Hypertrophy of the left atrium:bifurcation and increase in the amplitude of the P waves (P-mitrale); an increase in the amplitude and duration of the second negative (left atrial) phase of the P wave in lead V (less often V) or the formation of negative P; negative or biphasic (+ -) P wave (variable sign); increase in the total duration (width) of the P wave - more than 0.1 s.
2. Hypertrophy of the right atrium:in leads II, III, aVF, the P waves are high-amplitude, with a pointed apex (P-pulmonale); in leads V, the P wave (or at least its first - the right atrial phase) is positive with a pointed apex (P-pulmonale); in leads I, aVL, V, the P wave of low amplitude, and in aVL it can be negative (non-permanent sign); the duration of the P waves does not exceed 0.10 s.
3. Left ventricular hypertrophy:an increase in the amplitude of the R and S wave. In this case, R2
4. Hypertrophy of the right ventricle:displacement of the electrical axis of the heart to the right (angle α more than 100 °); an increase in the amplitude of the R wave in V and the S wave in V; the emergence of a QRS complex of the rSR ′ or QR type in lead V; signs of rotation of the heart around the longitudinal axis in a clockwise direction; displacement of the RS-T segment downward and the appearance of negative T waves in leads III, aVF, V; an increase in the duration of the interval of internal deviation in V more than 0.03 s.
Electrocardiogram for ischemic heart disease.
1. Acute stage of myocardial infarctioncharacterized by the rapid, within 1-2 days, the formation of a pathological Q wave or QS complex, displacement of the RS-T segment above the isoline and merging with it at first a positive and then negative T wave; after a few days the RS-T segment approaches the isoline. At the 2-3rd week of the disease, the RS-T segment becomes isoelectric, and the negative coronary T wave sharply deepens and becomes symmetrical, pointed.
2. In the subacute stage of myocardial infarctiona pathological Q wave or a QS complex (necrosis) and a negative coronary T wave (ischemia) are recorded, the amplitude of which gradually decreases from the 20th to 25th day. The RS-T segment is located on the isoline.
3. Cicatricial stage of myocardial infarctioncharacterized by the persistence over a number of years, often throughout the patient's life, of a pathological Q wave or QS complex and the presence of a weakly negative or positive T wave.
Save on social networks:Einthoven proposed to determine the angle between the horizontal line (parallel to the I-lead axis) drawn through the center of the triangle, and the electric axis - the angle a to describe the location of Aqrs in the frontal plane. He marked the left end of the horizontal line (the positive pole of the I axis of the lead) 00, the right end ± 180 °. The lower end of the perpendicular, crossing the horizontal line in the center, he designated + 90 °, the upper end -90 °. Now with a simple protractor, laid along the horizontal axis, you can determine the angle a. In our example, the angle a \u003d + 40 °.
The same method it is possible to determine the position of the electrical axis (mean vector) of the ventricular repolarization (AT) - angle a. and the electrical axis of excitation of the atria (Ap) is the angle a in the frontal plane.
Electrical axis position can be determined by the Dyeda scheme. Pre-calculate the algebraic sum of the amplitude of the teeth of I and III leads in millimeters. The resulting values \u200b\u200bare then deposited on the corresponding sides of the circuit. The intersections of the grid with the radial lines indicate the value of the angle a.
For this purpose, R. Ya. Pismenny's tables and others are also used.
It is accepted to consider normal position of the electric axis in the segment from + 30 ° to + 69 °. The location of the electric axis in the segment from 0 ° to + 29 ° is considered horizontal. If the electrical axis is located to the left of 0 ° (in the -1 ° -90 ° quadrant), it is said to deviate to the left. The location of the electric axis in the segment from + 70 ° to + 90 ° is considered vertical. They talk about the deviation of the electric axis to the right when it is located to the right of + 90 ° (in the right half of the coordinate system).
Normal ECG reflects the correct sequence of excitation of the heart, the normal orientation of the EMF vectors of their excitation, which is characteristic of the sinus rhythm, and therefore the standard relationship between the direction and amplitude of the teeth in different leads. and also the normal duration of intervals between cycles and within cycles.
The figure shows ECG healthy woman G. 32 years old. The sinus rhythm is correct, the heart rate is 62 in 1 min. (R - R \u003d 0.95 sec.). P - Q \u003d 0.13 sec. P \u003d 0.10 sec. QRS \u003d 0.07 sec. Q - T \u003d 0.38ex. RII\u003e R\u003e RIII. In the frontal plane, the location of the AQRS \u003d + 52 °. AT \u003d + 39 °. QRS - T \u003d 13 °. AR \u003d + 50. The amplitude of the P wave \u003d 1.5 mm. РII\u003e РI\u003e РIII. The P wave is two-phase, the first (positive) phase is greater than the second (negative).
QRS complex I, II, aVL type qRs... QRSIII type R, q, „aVL and SI, II are small. R, u slightly serrated on the descending knee. RS type QRSV1-V3 complex (rS). QRSV4_v6 of type qRs. SV2 \u003d 18 mm\u003e SV3\u003e SV5, rv1 tooth
Normal electrocardiogram
An electrocardiogram is normal, regardless of the lead system, consists of three upward (positive) P, R and T waves, two downward (negative) waves and Q and S, and an inconsistent, upward U wave.
In addition, the ECG distinguishes between the intervals P-Q, S-T, T-P, R-R and two complexes - QRS and QRST (Fig. 10).
Figure: 10. Teeth and intervals of normal ECG
P wave reflects depolarization of the atria. The first half of the P wave corresponds to the excitation of the right atrium, the second half - to the excitation of the left atrium.
P-Q interval corresponds to the period from the onset of atrial excitation to the onset of ventricular excitation. The PQ interval is measured from the beginning of the P wave to the beginning of the Q wave, in the absence of the Q wave, to the beginning of the R wave. It includes the duration of atrial excitation (the P wave itself) and the duration of the propagation of excitation mainly along the atrioventricular node, where there is a physiological delay in impulse conduction ( segment from the end of the P wave to the beginning of the Q wave). During the passage of the impulse through a specifically conducting system, such a small potential difference arises that no reflections of it on the ECG taken from the body surface can be detected. The P-Q interval is located on the isoelectric line, its duration is 0.12-0.18 s.
QRS complex reflects the depolarization of the ventricles. The duration (width) of the QRS complex characterizes intraventricular conduction, which varies within normal limits depending on the heart rate (decreases with tachycardia, and increases with bradycardia). The duration of the QRS complex is 0.06-0.09 s.
Q wave corresponds to the excitation of the interventricular septum. Normally, it is absent in the right chest leads. A deep Q wave in lead III appears with a high position of the diaphragm, disappearing or decreasing with a deep breath. The duration of the Q wave does not exceed 0.03 s, its amplitude is no more than 1/4 of the R wave.
R wave characterizes the excitation of the bulk of the ventricular myocardium, the S wave - excitation of the posterior upper parts of the ventricles and the interventricular septum. An increase in the height of the R wave corresponds to a rise in potential within the electrode. At the moment when the entire myocardium adjacent to the electrode is depolarized, the potential difference disappears and the R wave reaches the isoelectric line or passes into the S wave located below it (internal deviation, or internal deflection). In unipolar leads, the segment of the QRS complex from the beginning of excitation (the beginning of the Q wave, and in its absence - the beginning of the R wave) to the apex of the R wave reflects the true excitation of the myocardium at this point. The duration of this segment is called the internal deviation time. This time depends on the speed of propagation of excitation and the thickness of the myocardium. Normally, it is 0.015-0.035 s for the right ventricle, and 0.035-0.045 s for the left ventricle. The time lag of internal deviation is used to diagnose myocardial hypertrophy, pedicle blockade and its localization.
When describing the QRS complex, in addition to the amplitude of its constituent teeth (mm) and duration (s), their letter designation is given. In this case, small teeth are designated by lowercase letters, large ones by uppercase ones (Fig. 11).
Figure: 11. The most common forms of the complex and their letter designation
The S-T interval corresponds to the period of complete depolarization when there is no potential difference, and therefore is on the isoelectric line. A variation of the norm can be a displacement of the interval in standard leads by 0.5-1 mm. The length of the S-T interval varies widely with heart rate.
T wave is the final part of the ventricular complex and corresponds to the phase of ventricular repolarization. It is directed upwards, has a gently sloping ascending knee, a rounded apex and a steeper descending knee, that is, it is asymmetrical. The duration of the T wave varies widely, averaging 0.12-0.16 s.
QRST complex (Q-T interval) in time corresponds to the period from the beginning of depolarization to the end of repolarization of the ventricles and reflects their electrical systole.
Calculation of the Q-T interval can be performed using special tables. The duration of the QRST complex in normal conditions almost coincides with the duration of mechanical systole.
To characterize the electric systole of the heart, the systolic indicator SP is used - expressed as a percentage, the ratio of the duration of the electric systole Q-T to the duration of the cardiac cycle R-R:
An increase in the systolic index by more than 5% above the norm can be one of the signs of defective heart muscle function.
U wave occurs 0.04 s after the T wave. It is small, with normal amplification, it is not determined on all ECGs and mainly in leads V2-V4. The genesis of this prong is unclear. Perhaps it is a reflection of the trace potential in the phase of increased myocardial excitability after systole. The maximum amplitude of the U wave is normally 2.5 mm, the duration is 0.3 s.
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What ECG Draws
A conventional electrocardiographic study includes registration of EMF in 12 leads:
- standard leads (I, II, III);
- enhanced leads (aVR, aVL, aVF);
- chest leads (V1..V6).
In each lead, at least 4 ECG complexes (complete cycles) are recorded. In Russia, the standard for the belt speed of 50 mm / s is adopted (abroad - 25 mm / s). At a belt speed of 50 mm / s, each small cell located between adjacent vertical lines (distance 1 mm) corresponds to an interval of 0.02 s. Every fifth vertical line on the electrocardiographic tape is thicker. The constant tape speed and the millimeter grid on paper allow you to measure the duration of ECG waves and intervals and the amplitude of these waves.
Due to the fact that the polarity of the axis of lead aVR is opposite to the polarity of the axes of the standard leads, the EMF of the heart is projected onto the negative part of the axis of this lead. Therefore, in normal lead aVR, the P and T waves are negative, and the QRS complex looks like QS (less often rS).
Left and Right Ventricular Activation Time - the period from the beginning of the excitation of the ventricles to the coverage of the excitation of the maximum number of their muscle fibers. This is the time interval from the beginning of the QRS complex (from the beginning of the Q or R wave) to the perpendicular dropped from the top of the R wave to the isoline. The activation time of the left ventricle is determined in the left chest leads V5, V6 (the norm is no more than 0.04 s, or 2 cells). The activation time of the right ventricle is determined in the chest leads V1, V2 (the norm is no more than 0.03 s, or one and a half cells).
ECG teeth are denoted in Latin letters. If the amplitude of the prong is more than 5 mm, such a prong is indicated by a capital letter; if less than 5 mm - lowercase. As can be seen from the figure, a normal cardiogram consists of the following sections:
- p wave - atrial complex;
- pQ interval - the time of passage of excitation through the atria to the ventricular myocardium;
- qRS complex - ventricular complex;
- wave q - Excitation of the left half of the interventricular septum;
- r wave - the main wave of the ECG, due to the excitation of the ventricles;
- s wave - the final excitement of the base of the left ventricle (inconsistent ECG wave);
- sT segment - corresponds to the period of the cardiac cycle when both ventricles are engulfed in excitement;
- t wave - recorded during ventricular repolarization;
- qT interval - electrical systole of the ventricles;
- u wave - the clinical origin of this tooth is not exactly known (it is not always recorded);
- tP segment - diastole of the ventricles and atria.
Small R-wave growth is a common ECG symptom that is often misinterpreted by doctors. Although this symptom is usually associated with anterior myocardial infarction, it can also be caused by other non-infarction conditions.
A small increase in the R wave is detected in approximately 10% of hospitalized adult patients and is the sixth most common ECG abnormality (19,734 ECGs were collected by Metropolitan Life Insurance Company over a 5 5 year period). Besides, one third of patients with previous anterior myocardial infarction may only have this symptom on the ECG. Thus, the elucidation of specific anatomical equivalents of this electrocardiographic phenomenon is of great clinical importance.
Before analyzing the changes in the R waves, it is necessary to recall several theoretical foundations that are necessary to understand the genesis of ventricular activation in the chest leads. Ventricular depolarization usually begins in the middle of the left part of the interventricular septum, and is directed forward and left to right. This initial vector of electrical activity appears in the right and middle chest leads (V1-V3) as a small r wave (the so-called " septal r wave").
A small increase in the R wave can occur when the initial depolarization vector decreases in magnitude or is directed backward. After activation of the septum, left ventricular depolarization dominates the rest of the depolarization process. Although depolarization of the right ventricle occurs simultaneously with the left, its strength is negligible in the heart of a normal adult. The resulting vector will be directed from leads V1-V3, and will show up as deep S waves on the ECG.
Normal distribution of R-waves in the chest leads.
In lead V1, the ventricular complexes are rS-type with a steady increase in the relative size of the R waves to the left leads and a decrease in the amplitude of the S waves. Leads V5 and V6 tend to exhibit a qR-type complex, with the amplitude of the R waves in V5 higher than in V6 due to attenuation of the signal by the lung tissue.Normal variations include: narrow QS and rSr "patterns in V1, and qRs and R patterns in V5 and V6. At some point, usually at V3 or V4, the QRS complex begins to change from predominantly negative to predominantly positive and the R / S ratio becomes\u003e 1. This zone is known as " transition zone ". In some healthy people, the transition zone can be seen already in V2. This is called" early transition zone ". Sometimes the transition zone can be delayed until V4-V5, this is called" late transition zone ", or " transition zone delay ".
Normal R wave height in lead V3 is usually more than 2 mm
... If the height of the R waves in leads V1-V4 is extremely small, it is said that there is "insufficient or small increase in the R wave".
In the literature, there are various definitions of small increment of R-waves, criteria such asr waves less than 2-4 mm in leads V3 or V4 and / or the presence of a reverse growth of the R wave (RV4< RV3 или RV3 < RV2 или RV2 < RV1 или любая их комбинация).
In myocardial necrosis due to infarction, a certain amount of myocardial tissue becomes electrically inert and unable to generate normal depolarization. Depolarization of the surrounding tissues of the ventricles at this time increases (since there is no longer resistance to them), and the resulting depolarization vector is reoriented in the direction from the necrosis zone (in the direction of unimpeded spread). With anterior myocardial infarction, Q waves appear in the right and middle leads (V1-V4). However, in a significant number of patients, Q waves are not preserved.
In documented cases of previous anterior myocardial infarction, a small increase in the R wave is detected in 20-30% of cases . The average time for the complete disappearance of pathological Q waves is 1.5 years.
Noteworthy decrease in the amplitude of the R wave in lead I ... Up to 85% of patients with previous anterior myocardial infarction and low R-wave growth have either amplitude of R waves in lead I<= 4 мм or r-wave amplitude in lead V3<= 1,5 мм ... The absence of these amplitude criteria makes the diagnosis of anterior myocardial infarction unlikely (with the exception of 10% -15% of cases of anterior myocardial infarction).
If there is a small increase in the R waves in the chest leads, violation of repolarization (ST-T changes) in leads V1-V3 will increase the likelihood of diagnosing old anterior myocardial infarction.
Other possible causes of insufficient R-wave growth in the chest leadsare:
- complete / incomplete left bundle branch block,
- blockade of the anterior branch of the left bundle branch,
- wolff-Parkinson-White phenomenon,
- some types of right ventricular hypertrophy (especially those associated with COPD),
- left ventricular hypertrophy
- right ventricular hypertrophy type C.
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| Acute anterior MI |
Another common cause of a small increase in the R wave is improper placement of the electrodes: too high or too low location of the chest electrodes, the location of the electrodes from the limbs on the trunk.
Most often, the high position of the right chest electrodes leads to insufficient growth of the R waves. When the electrodes are moved to their normal position, the normal growth of the R waves is restored, however with old anterior myocardial infarction, QS complexes will persist
.
Unfortunately, these criteria turned out to be of little use for diagnosis and give a lot of false-negative and false-positive results.
A relationship was found between a small increase in the R wave on the ECG and diastolic dysfunction in patients with diabetes mellitus; therefore, this symptom may be an early sign of LV dysfunction and DCM in diabetics.
References.
- Electrocardiographic Poor R-Wave Progression. Correlation with Postmortem Findings. Michael I. Zema, M.D., Margaret Collins, M.D .; Daniel R. Alonso, M. D .; Paul Kligfield, M.D. CHEST, 79: 2, FEBRUARY, 1981
- Diagnostic value of poor R-wave progression in electrocardiograms for diabetic cardiomyopathy in type 2 diabetic patients / CLINICAL CARDIOLOGY, 33 (9): 559-64 (2010)
- Poor R Wave Progression in the Precordial Leads: Clinical Implications for the Diagnosis of Myocardial Infarction NICHOLAS L. DePACE, MD, JAY COLBY, BS, A-HAMID HAKKI, MD, FACC, BRUNOMANNO, MD, LEONARD N. HOROWITZ, MD, FACC , ABDULMASSIH S. ISKANDRIAN, MD, FACC. JACC Vol. 2.No. 6 December 1983 "1073- 9
- Poor R-Wave Progression. J Insur Med 2005; 37: 58-62. Ross MacKenzie, MD
- Dr. Smith "s ECG Blog. Monday, June 6, 2011
- Dr. Smith "s ECG Blog. Tuesday, July 5, 2011
- http://www.learntheart.com/ Poor R Wave Progression (PRWP) ECG
- http://clinicalparamedic.wordpress.com/ R-Wave Progression: Is it important? YOU BET !!
It will allow you to monitor the state of your heart and monitor the ECG. Follow the signs of a normal ECG. You do the research and after 30 seconds you get an automatic conclusion about the state of your heart. If necessary, you can send the study to the doctor's control.
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ECG is the main method for diagnosing heart rhythm disorders. This publication summarizes signs of a normal ECG. The ECG is recorded in a position comfortable for the patient, breathing should be calm. For recording an ECG, 12 main leads are most often used: 6 from the limbs and 6 from the chest. The project proposes an analysis of microalternations in six leads (only electrodes placed on the limbs are used), which make it possible to independently identify probable deviations in the work of the heart. Using the project, an analysis of 12 leads is also possible. But at home, it is difficult for an untrained person to correctly position the chest electrodes, which can lead to incorrect recording of the electrocardiogram. Therefore, the device CARDIOVISOR, which records 12 leads, is purchased by cardiologists.
To obtain 6 standard leads, the electrodes are applied as follows:
... Lead I: left hand (+) and right hand (-)
... Lead II: left leg (+) and right arm (-)
... Lead III: left leg (+) and left arm (-)
... aVR - enhanced right-hand lead (short for augmented voltage right).
... aVL - enhanced left arm abduction
... aVF - enhanced abduction from the left leg
The figure shows the electrocardiogram received by the client in the project site
Each lead characterizes the work of a certain part of the myocardium. I and aVL leads reflect the potentials of the anterior and lateral walls of the left ventricle. Leads III and aVF reflect the potentials of the inferior diaphragmatic (posterior) wall of the left ventricle. Lead II is intermediate, confirms changes in the anterolateral or posterior wall of the left ventricle.
The heart has two atria and two ventricles. The mass of the atria is much less than the mass of the ventricles, so the electrical changes associated with atrial contraction are small. They are associated with the P wave. In turn, with depolarization of the ventricles, high-amplitude oscillations are recorded on the ECG - this is the QRS complex. The T wave is associated with the return of the ventricles to rest.
When analyzing the ECG, a strict sequence is followed:
... Heart rhythm
... Intervals reflecting conductivity
... Electrical axis of the heart
... Description of QRS complexes
... Description of ST segments and T waves
Heart rate and heart rate
Heart rate is an important indicator of heart function. Normally, the rhythm is sinus (the name is associated with the sinus node - the pacemaker, thanks to which the impulse is transmitted and the heart contracts). If depolarization does not begin in the sinus node, then they speak of arrhythmia and the rhythm is named after the department from which depolarization begins. The heart rate (HR) is determined on the ECG by the distance between the R waves. The heart rate is considered normal if the duration of the R-R intervals is the same or has a slight scatter (up to 10%). The normal heart rate is 60-80 beats per minute. The ECG machine feeds paper at 25mm / s, so a large square (5mm) corresponds to 0.2 seconds (s) or 200 milliseconds (ms). Heart rate is measured by the formula
Heart rate \u003d 60 / R-R,
where R-R is the distance between the tallest teeth associated with ventricular contraction.
The acceleration of the rhythm is called tachycardia, and the deceleration is called bradycardia.
The ECG analysis should be performed by a cardiologist. Using the CARDIOVISOR, the project client can take an ECG on his own, since all calculations are performed by a computer program, and the patient already sees the final result analyzed by the system.
Intervals reflecting conductivity
By the intervals between the P-QRS-T waves, one can judge the conduction of an electrical impulse between the parts of the heart. The normal PQ interval is 120-200 ms (3-5 small squares). By the PQ interval, one can judge about the conduction of an impulse from the atria through the atrioventricular (atrioventricular) node to the ventricles. The QRS complex characterizes ventricular excitation. The width of the QRS complex is measured from the beginning of the Q wave to the end of the S wave. Normally, this width is 60-100 ms. Also look at the nature of the teeth of this complex. Normally, the Q wave in duration should be no more than 0.04 s and not exceed 3 mm in depth. An abnormal Q wave may indicate myocardial infarction.
QT interval characterizes the total duration of the systole (contraction) of the ventricles. QT includes the interval from the beginning of the QRS complex to the end of the T wave. Bazett's formula is often used to calculate the QT interval. This formula takes into account the dependence of the QT interval on the frequency of the rhythm (QTc). The normal QTc interval is 390-450 ms. Prolongation of the QT interval indicates the development of ischemic heart disease, atherosclerosis, rheumatism, or myocarditis. A shortened QT interval may indicate hypercalcemia.
All intervals reflecting the conductivity of the electrical impulse are calculated by a special program, which makes it possible to obtain fairly accurate examination results, which are visible in the system diagnostic room mode.
Electric axis of the heart (EOS)
Determination of the position of the electrical axis of the heart allows you to identify areas of impaired conduction of an electrical impulse. The assessment of the EOS position is carried out by cardiologists. When used, data on the position of the electrical axis of the heart are calculated automatically and the patient can view the result in his diagnostic room. To determine the EOS, look at the height of the teeth. Normally, the R wave should be larger than the S wave (read from the isoline) in leads I, II and III. Deviation of the axis to the right (the S wave is greater than the R wave in lead I) indicates problems in the work of the right ventricle, and deviations to the left (the S wave is larger than the R wave in leads II and III) may indicate left ventricular hypertrophy.
Description of the QRS complex
The QRS complex arises due to the conduction of an impulse along the septum and myocardium of the ventricles and characterizes their work. Normally, there is no pathological Q wave (no wider than 20-40 ms and no deeper than 1/3 of the R wave). In lead aVR, the P wave is negative and the QRS complex is oriented downward from the isoelectric line. The width of the QRS complex normally does not exceed 120 ms. An increase in this interval may indicate a blockade of the bundle branch (conduction disturbance).
Drawing. Negative P wave in lead aVR (isoelectric line is indicated in red).
P wave morphology
The P wave reflects the propagation of an electrical impulse in both atria. The initial part of the P wave characterizes the activity of the right atrium, and the final part characterizes the activity of the left atrium. Normally, the P wave should be positive in I and II leads, aVR - negative, usually positive in aVF and inconsistent in III and aVL leads (can be positive, inverted or biphasic). The width of the P wave is normally at least 0.12 s (120 ms). With an increase in the width of the P wave, as well as its doubling, we can talk about a violation of the impulse conduction - an atrioventricular block occurs (figure).
Drawing. Doubling and increasing the width of the P-wave
Description of ST segments and T waves
ST segment corresponds to the period when both ventricles are completely covered by excitation, measured from the end of the S to the beginning of the T wave. ST duration depends on heart rate. Normally, the ST segment is located on the isoline, ST depression is allowed up to 0.5 mm, its rise in standard leads should not exceed 1 mm. Elevation of the ST segment is observed in acute infarction and pericarditis, and depression indicates myocardial ischemia or the effect of cardiac glycosides.
T wave characterizes the process of repolarization (return of the ventricles to their original state). During normal heart function, the T wave is directed upward in leads I and II, but in lead aVR it will always be negative. A high and pointed T wave is observed with hyperkalemia, and a flat and elongated wave indicates the opposite process - hypokalemia. A negative T wave in leads I and II may indicate ischemia, infarction, right and left ventricular hypertrophy, or pulmonary embolism.
Above are the basic parameters that are used to analyze the ECG using the standard method. The project offers ECG analysis based on the dispersion mapping method. It is based on the formation of an information-topological model of small ECG oscillations - microalterations of the ECG signal. The analysis of these deviations makes it possible to detect pathology in the work of the heart at earlier stages, in contrast to the standard method of ECG analysis.
Rostislav Zhadeikospecially for the project.
The state of the whole organism depends on the health of the cardiovascular system. When unpleasant symptoms occur, most people seek medical attention. Having received the results of an electrocardiogram on their hands, few people understand what is at stake. What does the p wave reflect on the ECG? What alarming symptoms require medical supervision and even treatment?
Why is an electrocardiogram performed?
After the examination by the cardiologist, the examination begins precisely with the electrocardiography. This procedure is very informative, despite the fact that it is carried out quickly, does not require special training and additional costs.
An electrocardiogram is always taken upon admission to the hospital
The cardiograph records the passage of electrical impulses through the heart, registers the heart rate and can detect the development of serious pathologies. The teeth on the ECG give a detailed idea of \u200b\u200bthe different parts of the myocardium and how they work.
The norm for an ECG is that different teeth differ in different leads. They are calculated by determining the value relative to the projection of the EMF vectors on the lead axis. The prong can be positive and negative. If it is located above the cardiography isoline, it is considered positive, if below it, it is negative. A biphasic tooth is recorded when, at the moment of excitation, the tooth passes from one phase to another.
Important! An electrocardiogram of the heart shows the state of the conductive system, which consists of bundles of fibers through which impulses pass. Observing the rhythm of the contractions and the peculiarities of the rhythm disturbance, you can see various pathologies.
The conducting system of the heart is a complex structure. It consists of:
- sinoatrial node;
- atrioventricular;
- legs of the bundle of His;
- purkinje fibers.
The sinus node, as a pacemaker, is the source of impulses. They are formed at a rate of 60-80 times per minute. With various disorders and arrhythmias, impulses can be generated more often or less often than normal.
Sometimes bradycardia (slow heartbeat) develops due to the fact that another part of the heart takes over the function of the pacemaker. Arrhythmic manifestations can also be caused by blockages in various areas. Because of this, the automatic control of the heart is impaired.
What the ECG shows
If you know the norms for cardiogram indicators, how the teeth should be located in a healthy person, you can diagnose many pathologies. This examination is carried out on an inpatient basis, on an outpatient basis and in emergency critical cases, by ambulance doctors to make a preliminary diagnosis.
Changes reflected in the cardiogram may indicate the following conditions:
- rhythm and heart rate;
- myocardial infarction;
- blockade of the cardiac conduction system;
- violation of the exchange of important trace elements;
- blockage of large arteries.
Obviously, an electrocardiogram study can be very informative. But what are the results of the data obtained?
Attention! In addition to the teeth, there are segments and intervals in the ECG picture. Knowing what is the norm for all these elements, you can make a diagnosis.
Detailing the decoding of the electrocardiogram
The norm for the P wave is the location above the isoline. This atrial tooth can be negative only in leads 3, aVL and 5. In leads 1 and 2 it reaches its maximum amplitude. The absence of a P wave may indicate a serious disturbance in impulse conduction in the right and left atrium. This tooth reflects the state of this particular part of the heart.
The P wave is deciphered first, since it is in it that an electrical impulse is generated that is transmitted to the rest of the heart.
Cleavage of the P wave, when two apices are formed, indicates an increase in the left atrium. Bifurcation often develops in pathologies of the bicuspid valve. The double-humped P wave becomes an indication for additional cardiac examinations.
The PQ interval shows how the impulse is transferred to the ventricles through the atrioventricular node. The norm for this section is a horizontal line, since there are no delays due to good conductivity.
The Q wave is normally narrow, its width is no more than 0.04 s. in all leads, and the amplitude is less than a quarter of the R wave. If the Q wave is too deep, this is one of the possible signs of a heart attack, but the indicator itself is assessed only in combination with others.
The R wave is ventricular, so it is the highest. The walls of the organ in this zone are the densest. As a result, the electric wave travels the longest. Sometimes it is preceded by a small negative Q wave.
During normal heart function, the highest R wave is recorded in the left chest leads (V5 and 6). Moreover, it should not exceed 2.6 mV. Too high a tooth is a sign of left ventricular hypertrophy. This condition requires in-depth diagnostics to find out the reasons for the increase (IHD, arterial hypertension, valvular heart disease, cardiomyopathy). If the R wave drops sharply from V5 to V6, this could be a sign of MI.
After this reduction, the recovery phase begins. On the ECG, this is illustrated as the formation of a negative S wave. After a small T wave, an ST segment follows, which should normally be represented by a straight line. The Tckb line remains straight, there are no bent areas on it, the condition is considered normal and indicates that the myocardium is completely ready for the next RR cycle - from contraction to contraction.
Determination of the heart axis
Another step in decoding the electrocardiogram is to determine the axis of the heart. A normal tilt is between 30 and 69 degrees. Smaller indicators indicate a deviation to the left, and larger ones - to the right.
Possible research errors
It is possible to obtain inaccurate data from the electrocardiogram if, when registering signals, the cardiograph is affected by the following factors:
- fluctuations in the frequency of alternating current;
- displacement of the electrodes due to their loose overlap;
- muscle tremors in the patient's body.
All these points affect obtaining reliable data during electrocardiography. If the ECG shows that these factors have taken place, the study is repeated.
A timely visit to a doctor for advice will help diagnose pathologies in the early stages. When a cardiogram is decoded by an experienced cardiologist, you can get a lot of valuable information. In order not to start the pathology, it is important to consult a doctor at the first painful symptoms. So you can preserve health and life!
Still:
Causes of a negative T wave on the ECG, possible heart diseases and the degree of their influence on the indicator