Embedded Files
what is an ECG?
Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. In the healthy state, an ECG records predictable, reproducible waves and complexes, which correspond to electromechanically coupled physiologic events in the heart. Under pathologic conditions, the ECG can detect arrhythmias, ischemia, inflammation, and more.
How do we apply the ECG on a patient to masur the cardiac electrical activity?
How do we apply the ECG on a patient to masur the cardiac electrical activity?
The ECG unit is consisting of:
Electrodes (leads)
Wiers
Recording deceives.
Analysis software
Recording paper
The Electrodes: it is affixed to the skin with adhesive backing.
10 Electrodes are required to produce 12-Lead ECG
one electrode is affixed to each limb.
Six electrodes are placed on the pericardium:
V1 intercostal space 4 on the right margin of the sternum
.2 intercostal space 4 on the left margin of the sternum
V4 intercostal space 5 midclavicular line
. V3 midway between V2 and V4
V5 intercostal space 5 anterior axillary line
V6 intercostal space 5 midaxillary line
12 lead is created by ECG software :
3 bipolar limb leads (recording obtained from pairs of limb electrodes ) :
1 : Right arme - and left arm +
2 : Right arm - and left leg +
3: left arm - and left leg +
(Right leg is for discharging)
Einthoven triangle
3 augmented unipolar limb led to recording obtained from a limb electrode and the central terminal.
Vector Right aVR : Right arm + and the central terminal -
Vector left aVL : left arm - to central terminal +
Vector foot aVF : left leg + to terminal -
6 precordial leads (recording obtained from the corresponding chest electrode and the central terminal):
V1, V2: septal leads
V3, V4: anterior leads
V5, V6: lateral leads
Obs : Any electrical activity has tow properties to be measured, The strongness and direction. The aim of using the leds and electrodes is to figur out how and where the cardiac charges go.
Tracing of ECG, the Register properties:
It is organized as a graph box with small and large squares. The small box = 1x1 mm and the large box is 5x5 mm.
. X and Y axis: the X axis is the time in second and Y is Voltage in mV
X axis utility :
ECG tracing Speed is 25 mm \ sec or 25 small boxes or 5 large per sec
Obs : 1 small box is 0.04 S and the large box is 0.2 S
From X axis we can determine if there is Bradycardia or tachycardia. If the Rythm is regular or irregular. And to calculate if the haret rate.
Y axis utility:
1 small box has 0.1 mV. It is allowing for determination of voltage amplitude of ECG waveforms. The amplitude correlates with electromechanically coupled events in the cardiac cycle :
No deflection = no cardiac conduction or contraction e.g. isoelectric baseline
Small deflection = low voltage associated with thin myocardium atria and modest contraction, P wave
Large deflection = high voltage associated with thick myocardium ventricle and forceful contraction, QRS complex.
Page updated
Google Sites
Report abuse