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Analysis of ECG. Electrocardiography evaluation of heart work (ECG). Plan of Lecture :. 1 ) determination of the excitation source ; 2 ) evaluation of heart rate; 3 ) determination of heartbeat ing frequency; 4 ) evaluation of electrocardiogram voltage;
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Analysis of ECG Electrocardiography evaluation of heart work (ECG).
Plan of Lecture: 1) determination of the excitation source; 2) evaluation of heart rate; 3) determination of heartbeating frequency; 4) evaluation of electrocardiogramvoltage; 5) determination of the direction of the electrical axis; 6) analysis of ECG-elements
Electrocardiogram • It is the method of registration of heart bioelectrical potential from the chest of patient
To describe how elektrocardiograma in all areas of wave of de- and repolarization sending will look you must remember three rules • If the dipole vector directed towards the positive electrode of lead – ECG will show positive wave •If the dipole vector directed toward the negative electrode lead – elektrocardiogram will show negative wave •If the dipole vector is perpendicular to the axis of abduction, then elektrocardiogram writes isoline. Vector of dipole Positive lead-electrode Vector of dipole Vector of dipole Isoline
WAVES OF ECG ECG ELEMENTS 1. P wave – depolarization of atria, precedes atria systole 2. QRS wave is depolarization of ventricles, precedes ventricular systole 3. atria repolarization also occurs at QRS 4. T wave indicates ventricular repolarization
SEQUENCE AND PROCEDURE OF ECG ANALYSIS • Determination of the excitation source. To determine the excitation source (pacemaker) it is necessary to assess the progress of excitation within atrium and set the correlation between P-wave and ventricular complexes QRS. Normally, the electrical impulse arises in the sinus node and ECG standard lead II record positive P-wave before every complex QRS. • Evaluation of correctness of heart rate – based on duration comparing ofR-R-intervals. Normally observed an insignificant difference of duration within 0,1 sec • Determination of heart rate. With normal heart rate you should divide 60 seconds by the duration of R-R-interval in seconds • Evaluation voltage ECG. It is necessary to evaluate the amplitude of R-wave in the standard leads. If the amplitude of the R-wave in standard lead II more than 5 mm, or if the amount of R-wave amplitudes in the I, II and III standard leads is more than 15 mm, the voltage of ECG is maintained. • Determination of the electrical axis direction • Analysis of ECG elements
SIX-AXIS SYSTEM OF BAILEY Graphical method Calculate the algebraic sum of prongs amplitudes of the QRS-complex in I and III standard leads. Add it to randomly selected values on the axes of appropriate leads of 6-axis Bailey system of coordinate. From ends of these projections topostpone the perpendiculars. The point of their crossing connect with the the center of system. This line – is electric axis of the heart. The angle α is determined between this line and positive part of the axes I of the standard lead.
POSITIONS OF HEART ELECTRICAL AXIS IN NORM Intermediate
POSITIONS OF HEART ELECTRICAL AXIS IN NORM Vehorisontal
ANALISIS OF ECG ELEMENTS Analysis of P-wave includes: a ) evaluation of wave forms b ) measuring the amplitude and c) determine the duration. Analysis of segment interval and P -Q segment is measured from the end of P before Q. The interval is measured from the beginning of P to the Q. Analysis of the QRS complex includes: 1. Assessment of wave Q: a) measurement of its amplitude and compare it with the R wave amplitude in the same lead; b) measuring the length of wave Q 2. Assessment of wave R: a) measuring the amplitude and b) comparing it with Q wave amplitude in the same tooth extraction and other R leads. 3. Assessment of wave S: a) measuring the amplitude and b) comparing the amplitude of R wave in the same leads. Analysis of S-T segment . Analyzing segment , you must set its deviation from the isoline. Analysis of wave T. In the analysis of the T wave should: a) identify the direction, b) to assess its shape and c) to measure the amplitude. Analysis of the QT interval is to measure its duration (from the beginning to the end of QT).
FREQUENCY-AMPLITUDE CHARACTERISTICS OF THE P -WAVE, INTERVAL AND SEGMENT PQ. Prong R in leads I, II, aVF , V2-V6 it is always positive in a healthy person. In leads III, aVL , V1 – can be positive, biphasic. In lead aVR – always negative. The amplitude of the P wave – to 2,5 mm, and its duration does not exceed 0,1 s. Interval P -Q reflects a time of spread of excitation within atrium, atrioventricular node, Gis bundle and its branches. The duration of the interval P -Q varies from 0,12 to 0,20 s, depending on heart rate. Segment P -Q reflects a spread of excitation throuh the atrio -ventricular node, Gis bundle and its branches. Duration of segment P-Q is normal to 0,12 sec.
FREQUENCY-AMPLITUDE CHARACTERISTICS OF THE Q, R, S-WAVES Ventricular complexes ORST If the amplitude of prongs of ORS-complex more than 5 mm, they are given uppercase alphabet (Q, R, S), if less than 5 mm - capital letters (q, r, s). Duration of ventricular complex is 0,06-0,09 s in the standard leads Wave Q displays spread of excitation through the middle and lower thirds of the interventricular septum. It should not exceed 1/4 of prongs ʼ R amplitude in a healthy person, and its duration – 0,03 sec. But aVR-lead – is exception, where deep and wide Q-prong registered. Wave R normally registered in all standard and reinforced leads. In lead aVR R-prongslightly expressed or absent completely. In the precordial leads R-wavesʼ amplitude gradually increases from V1 - V4, and decreases in V5 - V6. Height of R wave does not exceed 20 mm in standard and reinforced leads, and 25 mm – in thoracic (pectoral). It displays the spread of excitation through the side walls of the right and left ventricles. Wave S Its amplitude in different leads varies in a wide range In a healthy person, but not exceeding 20 mm. Its duration – 0,03 s. Wave S decreases from V1, to V6 in the precordial leads. It displays the spread of excitation in the basal parts of the ventricles.
FREQUENCY-AMPLITUDE CHARACTERISTICS OF THE T-WAVE, ST-SEGMENT AND QT-INTERVAL S-T segment – reflects full coverage of both ventricles with stimulation. As usual segment S-T is on the isoline in standard and reinforced single-pole leads from limbs and its displacement is less than 0,5 mm. In thoracalis leads lV1 - V3 may be a slight shift acording to the isoline up to 2 mm, and in V4, 5,6 - shift down less than 0,5 mm. Wave T – normally always positive in leads I, II, aVF , V2 - V6, moreover T1 > TIII and TV6 > TV1 . It has aslope ascending and slightly steeper downward knee. In leads III, aVL and V1 – T wave may be positive, negative , or biphasic. In lead aVR negative T wave usually registers. The amplitude of the T wave is less than 5,6 mm in leads from limbs and 15-17 mm in precordial leads. The duration of the T wave – 0,16-0,24 s. Q- T interval . This is an electrical ventricular systole . Duration of Q- T interval depends on heart rate. The proper duration time of interval Q- T can be counted with the Bazett formula: Q- T = K · √ R-R, where K - coefficient of 0,37 for men and 0,40 for women; RR - duration of one cardiac cycle or intercyclic іnterval.
