Sparkfun Electronics AD8232 Hook-Up Manual page 4

Diagram of the heart. Credit Wikipedia.org
PR Interval
The PR interval is the initial wave generated by an electrical impulse traveling from the right atrium
to the left. The right atrium is the first chamber to see an electrical impulse. This electrical impulse
causes the chambers to "depolarize". This forces it to contract and drain deoxygenated blood from
both the Superior and Inferior vena cava into the right ventricle. As the electrical impulse travels
across the top of the heart it then triggers the left atrium to contract. The left atrium is responsible
for receiving newly oxygenated blood from the lungs into the left ventricle via the left and right
pulmonary veins. The pulmonary veins are red in the diagram because they are carrying
oxygenated blood. They are still called veins because veins carry blood towards the heart. Science!
QT Interval
The QT Interval is where things get really interesting. The QRS is a complex process that
generates the signature "beep" in cardiac monitors. During QRS both ventricles begin to pump. The
right ventricle begins to pump deoxygenated blood into the lungs through the left and right
pulmonary arteries. The pulmonary arteries are blue in the diagram because they are carrying
deoxygenated blood. They are still called arteries because arteries carry blood away the heart.
Science, Again! The left ventricle is also begining to pump freshly oxygenated blood through the
aorta and into the rest of the body. After the initial contraction comes the ST segment. The ST
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