Answer:
Electrocardiograph (ECG) ECG is a graphical representation
of the electrical activity of the heart during a cardiac cycle. A patient is
connected to the machine with three electrical leads (one to each wrist and to
the left ankle) that continuously monitor the heart activity. For a detailed
evaluation of the heart's function, multiple leads are attached to the chest
region. .
Each
peak in the ECG is identified with a letter from P to T that corresponds to a
specific electrical activity of the heart. The P-wave represents the,
electrical excitation (or depolarization) of the atria, which leads to the
contraction of both the atria. The QRS complex represents the depolarization of
the ventricles, which initiates the ventricular contraction.
The
contraction starts shortly after Q and marks the beginning of the systole.
The
T-wave represents the return of the ventricles from excited to normal state
(repolarisation). The end of the T-wave marks the end of systole. Obviously, by
counting the number of QRS complexes that occur in a given time period, one can
determine the heart beat rate of an individual. Since the ECGs obtained from
different individuals have roughly the same shape for a given lead
configuration, any deviation from this shape indicates a possible abnormality
or disease. Hence, it is of a great clinical significance.
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