When interpreting an ECG, the nurse would keep in mind which of the following about the P wave? Select all that apply.
A. Reflects electrical impulse beginning at the SA node.
B. Indicated electrical impulse beginning at the AV node.
C. Reflects atrial muscle depolarization.
D. Identifies ventricular muscle depolarization.
E. Has a duration of normally 0.11 seconds or less.
Correct Answer: A, C, E
In a client who has had an ECG, the P wave represents the activation of the electrical impulse in the SA node, which is then transmitted to the AV node. In addition, the P wave represents atrial muscle depolarization, not ventricular depolarization. The normal duration of the P wave is 0.11 seconds or less in duration and 2.5 mm or more in height.
Option A: The P wave and PR segment is an integral part of an electrocardiogram (ECG). It represents the electrical depolarization of the atria of the heart. It is typically a small positive deflection from the isoelectric baseline that occurs just before the QRS complex.
Option B: The P wave represents the electrical depolarization of the atria. In a healthy person, this originates at the sinoatrial node (SA node) and disperses into both left and right atria. Depolarization of the right atrium is responsible for the early part of the P wave, and depolarization of the left atrium is responsible for the middle and terminal portions of the P wave.
Option C: The PR interval represents the time between atrial depolarization and ventricular depolarization. Abnormalities in the timing of the PR segment can indicate pathology. The first deflection of the P wave normally appears between 120 and 200 milliseconds (ms) before the first upward deflection of the QRS complex. It is the first deflection from baseline voltage observed on an ECG.
Option D: This length between the P wave and QRS complex is represented by the PR interval, which is the time between the onset of atrial depolarization and the onset of ventricular depolarization. An ECG displaying sinus rhythm with a consistent PR interval greater than 200 ms and 1 to 1 relationship of P to QRS complexes without any dropped QRS complex is considered a first-degree atrioventricular (AV) block.
Option E: The first deflection of the P wave normally appears between 120 and 200 milliseconds (ms) before the first upward deflection of the QRS complex. It is the first deflection from baseline voltage observed on an ECG.
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