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Patterns and Wave

P wave

Tracing on an ECG that results from movement of depolarization wave from the SA node through the atria; atrial contraction follows.

QRS wave

Tracing on an ECG that results from ventricular depolarization. Atrial repolarization also occurs during this time; ventricular contraction follows.

T wave

Tracing on an ECG caused by ventricular repolarization; ventricular relaxation follows.

P-Q interval

Time required for conduction from SA node to Purkinje fibers

S-T Interval

Time when ventricular myocardia is undergoing slow depolarized
**(elevated S-T indicates acute myocardial infarction)

Q-T Interval

Time from start of ventricular depolarization to ventricular repolarization.
**(Lengthened by myocardial damage)

Atrial Depolarization


Ventricular Depolarization

QRS complex

Atrial Repolarization

Hidden in the QRS complex

Ventricular Repolarization


Isovolumetric Relaxation

The period during which the ventricles are relaxed and both AV and semilunar valves are still closed. The volume of the ventricles remains unchanged (isovolumetric) during this period.

Isovolumetric Contraction

Occurs when the AV valves are forced shut. During this brief period, while the semilunar valves are still closed, the volume of the ventricles remains unchanged.

End-Diastolic Volume

amount of blood a ventricle contains at the end of diastole, just before ventricular contraction occurs

Rapid Ventricular Filling

Occurs as blood flows into the empty and relaxed ventricles. Volume of the ventricles increases rapidly.


A slower filling event than that of Rapid Ventricular filling because most of the volume of the ventricle is already occupied by blood

Atrial Systole

0.1 second

Ventricular Systole

0.3 second

Relaxation Period

0.4 second

Ventricular Ejection

Occurs as the continuing contraction of the ventricles increases the pressure in the ventricles and forces the semilunar valves open. At this point, blood is forces out of the ventricles. This interval ends when the ventricles begin to relax, and the semilunar valves close. The closing of the semilunar valves causes a small increase in blood pressure visible as the dicrotic notch on a plot of blood pressure against time. The amount of blood remaining in the ventricles at this time is called the End-Systolic Volume (ESV)

End Systolic Volume

the amount of blood that remains in the ventricle at the end of ventricular systole

AV Valves Closed

Isometric ventricular relaxation, Isovolumetric Contraction, Ventricular Ejection

AV Valves Open

Rapid filling, diastasis, atrial systole, Ventricular Contraction

Semilunar Valves Closed

Isometric Ventricular Relaxation, Rapid filling, Diastisis, Atrial Systole, Isovolumetric contraction

Semilunar Valves Open

Ventricular Ejection

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