Transcript 18 Electrocardiography investigation of heart (ECG).

Electrocardiography
Electrocardiography
investigation
of heart
evaluation of heart work
(ECG).
(ECG).
Analysis of ECG
Plan of Lecture:
1. Formation of an electrogram of the heart muscle fibers
(electrocardiogram)
2. Formation of an electrocardiogram during sending of
excitation through the heart
3. Electrocardiographic leads:
a) standard;
b) enhanced;
c) pectoral;
4. Characteristic of normal electrocardiogram
5. Analysis of electrocardiogram:
a) determination of the excitation source;
b) evaluation of heart rate;
c) determination of heartbeating frequency;
d) evaluation of electrocardiogram voltage;
e) determination of the direction of the electrical axis;
f) 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
Vector of dipole
•
If the dipole vector is
perpendicular to the axis of
abduction, then
elektrocardiogram writes
isoline.
•
Positive leadelectrode
Vector of dipole
Vector of
dipole
Isoline
ECG time & voltage
•ECG machines can run at 50 or 25 mm/sec
•Major grid lines are 5 mm apart, at standard 25 mm/s, 5
mm corresponds to 20 seconds
•Minor lines are 1 mm apart, at standard 25 mm/s, 1 mm
corresponds to .04 seconds
•Voltage is measured on vertical axis
•Standard calibration is 0.1 mV per mm of deflection
Electrogram of cardiac muscle
ECG ELEMENTS
WAVES OF ECG
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
ECG LEADS
ECG LEADS
a) Bipolar limb leads. The bipolar limb leads record
the voltage between electrodes placed on the
wrists and legs. These leads were proposed by
Einthoven in 1913
I lead: left arm (+) - right arm (-);
II lead: left leg (+) - right arm (-);
III lead: left arm (+) - left leg (-)
For recording limb leads we put red electrode on
right arm, yellow - on left arm, green - on left leg
and black - on right leg. Black electrode has zero
potential (ground).
ECG LEADS
ECG LIMB LEADS
ECG AUGMENTED LIMB LEADS
ECG LEADS
ECG LEADS
The unipolar limb leads were proposed by
Goldberger in 1942. They record voltage
between single “exploratory electrode” from one
limb and zero joined electrode from two other
limbs. So there are three leads AVR, AVL, AVF.
In fact zero electrodes records middle voltage of
two limbs. Bipolar limb leads and unipolar limb
leads record electrical power in frontal
projection.
ECG LEADS
ECG LEADS
V1 - in crossing right IV right intercostal space
and parasternal line;
V2 - in crossing left IV intercostal space and
parasternal line;
V3 - between V2 and V4;
V4 - in crossing V left intercostal space and
medioclavicular line;
V5 - in crossing V left intercostal space and
anterior axilar line;
V6 - in crossing V left intercostal space and
middle axilar line.
ELECTROCARDIOGRAM
ECG leads
ECG LEADS
HOLTER MONITOR
SEQUENCE AND PROCEDURE OF ECG ANALYSIS
1. 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.
2. Evaluation of correctness of heart rate – based on duration comparing
of R-R-intervals. Normally observed an insignificant difference of duration
within 0,1 sec
3. Determination of heart rate. With normal heart rate you should divide
60 seconds by the duration of R-R-interval in seconds
4. Evaluation voltage ECG. It is necessary to evaluate the amplitude of Rwave 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.
5. Determination of the electrical axis direction
6. 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
Vertical
Intermediate
horisontal
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 wave Q:
a) measurement of its amplitude and compare it with the R wave amplitude in
the same lead;
b) measuring the length of prong 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.
Wave 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 waves 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 throught 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-wave registered.
Wave R normally registered in all standard and reinforced leads. In lead aVR Rprong slightly 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 throught 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-PRONG, 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.
Thank you!