P wave (electrocardiography)
P wave (electrocardiography)
The P wave in electrocardiography is a term that refers to the graphical representation of the electrical activity occurring in the atria (upper chambers) of the heart during a cardiac cycle.
Pronunciation
The term is pronounced as "pee wave".
Etymology
The term "P wave" is derived from the Latin word 'pulsus' which means 'beat', referring to the beating of the heart. The 'wave' part of the term refers to the wave-like pattern that the electrical activity forms on the electrocardiogram.
Definition
The P wave represents the first electrical activity of the heart in a cardiac cycle, which is the depolarization of the atria. This is the process by which the atria prepare for contraction, allowing for the pumping of blood into the ventricles (lower chambers of the heart).
Characteristics
A normal P wave is upright in leads I, II, aVF and V2-V6, and inverted in lead aVR. Its duration is usually less than 120 ms and its amplitude is less than 2.5 mm in the limb leads and less than 1.5 mm in the precordial leads.
Related Terms
- Electrocardiogram: A test that measures the electrical activity of the heartbeat.
- Atria: The two upper chambers of the heart.
- Ventricles: The two lower chambers of the heart.
- Depolarization: The process by which cells within the heart change from a more negative to a more positive membrane potential.
- Cardiac Cycle: The complete cycle of events in the heart from the beginning of one heart beat to the beginning of the next.
See Also
External links
- Medical encyclopedia article on P wave (electrocardiography)
- Wikipedia's article - P wave (electrocardiography)
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