ECG (Electrocardiogram) fully explained | Chapter circulation | Video 8
611.9 هزار بار بازدید -
4 سال پیش
-
Electrocardiogram
Electrocardiography
The process of
Electrocardiogram
Electrocardiography
The process of producing an electrocardiogram
Electrocardiogram
A recording of the electrical activity of the heart.
An electrocardiogram (ECG or EKG) is a test that checks how your heart is functioning by measuring the electrical activity of the heart. With each heartbeat, an electrical impulse (or wave) travels through your heart. This wave causes the muscle to squeeze and pump blood from the heart.
An ECG measures and records the electrical activity that passes through the heart. A doctor can determine if this electrical activity is normal or irregular.
An ECG may be recommended if you are experiencing arrhythmia, chest pain, or palpitations and an abnormal ECG result can be a signal of a number of different heart conditions.
What can you expect?
• An ECG is a non-invasive procedure, which means that nothing is injected into the body.
• It is painless.
• A number of electrodes – usually a total of 12 to 15 – are attached to various locations on your body including your arm, leg and chest.
• The electrodes are attached by small suction cups or adhesive patches.
• Sensors in the pads detect the electrical activity of your heart.
• The test is usually performed while you lie still.
• Results are most often recorded on graph paper and interpreted or read by your doctor or a technologist.
• The test usually takes 5 to 10 minutes.
P, Q, R, S, T Waves:
P Wave
The electrical activity of the heart originates in the sino-atrial node. The impulse then rapidly spreads through the right atrium to the atrioventricular node. It also spreads through the atrial muscle directly from the right atrium to the left atrium. The P-wave is generated by activation of the muscle of both atria.
Q, R, S Wave
The impulse travels very slowly through the AV node, then very quickly through the bundle of His, then the bundle branches, the Purkinje network, and finally the ventricular muscle.
The first area of the ventricular muscle to be activated is the interventricular septum, which activates from left to right. This generates the Q-wave.
Next, the left and right ventricular free walls, which form the bulk of the muscle of both ventricles, gets activated, with the endocardial surface being activated before the epicardial surface. This generates the R-wave.
A few small areas of the ventricles are activated at a rather late stage. This generates the S-wave.
Finally, the ventricular muscle repolarizes. This generates the T-wave.
To understand the morphology of the ECG waveforms one needs to appreciate only one biophysical fact: if a wavefront of depolarization travels towards the electrode attached to the + input terminal of the ECG amplifier and away from the electrode attached to the - terminal, a positive-going deflection will result. If the waveform travels away from the + electrode towards the - electrode, a negative going deflection will be seen.
1. A wave of depolarization traveling toward a positive electrode results in a positive deflection in the ECG trace.
2. A wave of depolarization traveling away from a positive electrode results in a negative deflection.
3. A wave of repolarization traveling toward a positive electrode results in a negative deflection.
4. A wave of repolarization traveling away from a positive electrode results in a positive deflection.
5. A wave of depolarization or repolarization traveling perpendicular to an electrode axis results no net deflection.
#Electrocardiography
#ElectricalActivityOfHeart
#HowECGIsPerformed
4 سال پیش
در تاریخ 1399/02/18 منتشر شده
است.
611,927
بـار بازدید شده