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Electrocardiograms
The heart undergoes a very complex process of
electrical
activity;
this
is
the
basis
for
how
electrocardiograms work. As the heart's muscles
contract, the cells are electrically depolarized causing a
cascade of depolarization to flow across the heart –
contracting the heart's muscle fibers.
During a heartbeat a complex series of events happen
which begin with the cells resting potential at roughly -90
mV (millivolts). The hearts Sinoatrial Node begins the
cascade by depolarizing – creating an electrical voltage.
The electrical signal travels to the right atrium and
almost immediately to the left atrium. Because the atria
and the ventricles are insulated from each other by a
special type of cell which acts as an electrical insulator,
the signal is picked up in another cluster of cells called
the Atrioventricular (AV) Node located in the right atria.
The signal is carried by a special type of fibers – the
Bundle of His into the ventricles. Purkinje fibers rapidly
spread the electrical depolarization cascade throughout
the ventricles. The entire event takes some time to
complete. The graph is a visual demonstration of the
heart's relative charge at any given point during
heartbeats.
The electrical voltage is measured on the skin using
conducting leads and it is converted into a graph that is
very standard and reproducible.
V2018.01
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