The nurse is examining the patient's cardiac rhythm strip in lead II and notices that all of the P waves are upright and look the same except one that has a different shape and is inverted
The nurse realizes that the P wave with the abnormal shape is probably: a. from the SA node since all P waves come from the SA node.
b. from some area in the atria other than the SA node.
c. indicative of ventricular depolarization.
d. normal even though it is inverted in lead II.
B
Normally a P wave indicates that the SA node initiated the impulse that depolarized the atrium. However, a change in the shape of the P wave may indicate that the impulse arose from a site in the atria other than the SA node. The P wave represents atrial depolarization. It is usually upright in leads I and II and has a rounded, symmetrical shape. The amplitude of the P wave is measured at the center of the waveform and normally does not exceed three boxes, or 3 millimeters, in height.
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