In this section...
In the lab...
History Timeline
Pathologies
EKG
Introduction
Short for electrocardiogram, the EKG measures the electrical activity throughout the heart. EKGs give an accurate graphic representation, or tracing, of the electrical activity going on in the heart.
The EKG is made by measuring the electrical potential between various points of the body using a galvanometer. In order to properly measure the electrical potential of various points of the body, ten lead electrodes are placed on the body. Each electrode records information from particular parts of the heart. Any differences in an EKG from the normal tracing usually indicate problems in the heart.
An EKG tracing corresponding with the movement of electrical impulses within the heart. (keep clicking to view the entire animation)
An EKG tracing of a normal, healthy heartbeat, like the one above, always consists of a P wave, a QRS complex, and a T wave.
An EKG Machine
The first small upward indentation is known as the “P wave.” The P wave represents the electrical impulse that indicates that the atria are contracting to pump the blood to the ventricles. The QRS complex is the short downward section connected to the tall upward section. The QRS complex represents the ventricles contracting to pump the blood out. The next short flat segment is known as the ST segment. This part indicates the amount of time from the end of the contraction of the ventricles to when the ventricles begin to contract for the next beat. The last upward curve indicates the ventricle recovery period. Variations in the size and length of these different segments usually indicate problems in those certain areas the segments represent.
EKG testing is a non-invasive way to test heart function. It is fast, easy, painless, and very effective. Doctors often use the EKG to narrow down heart pathologies including ischemia, heart attack, conduction disorders, pericarditis and electrolyte disturbances. EKGs are also used to check the function of implanted pacemakers, check the effectiveness of medications, and the overall status of the heart.
In the lab...
Safety Precautions: There are no general safety precautions related to EKGs, but in order for a clear tracing to be graphed, the patient must lie very still.
Orientation of Patient: First the doctor will place 10 separate lead electrodes on different parts of the patient’s body (six on the chest, and one on each limb, see above picture). The patient is then asked to lie down and the wires from the galvanometer will be connected to each individual electrode. The patient is then supposed to lie very still in order to obtain a clear tracing of the heart's electrical activity. Because talking disturbs tracing, patients are supposed to not talk while getting an EKG.
Length of Scan: The length of the scan depends entirely on whether the physician obtained a clear and proper tracing. If the patient did not lie still enough or the patient talks, the length of the scan is increased.
