Prepare for the NCLEX-RN® with today’s question focusing on a nurse who is assessing ECG readings for clients admitted to the cardiac unit. Which ECG tracing should the nurse recognize as a normal PQRST wave? Test your skills now!
The nurse is assessing ECG readings for clients admitted to the cardiac unit. Which ECG tracing should the nurse recognize as a normal PQRST wave?
A.
B.
C.
D.
Scroll down for the correct answer!
The correct answer to today’s NCLEX-RN® Question is…
C.
Rationale: This ECG tracing shows a normal PQRST wave. The P wave is present, regular in timing and shape, and there is one for each QRS complex. The PR interval is between 0.12 to 0.20 seconds, three to five little boxes. The QRS duration is less than 0.1 seconds, two and a half little boxes. The ST segment is not elevated or depressed by more than one small box. The T wave shape is asymmetric, and the height is less than five millimeters in precordial leads and less than ten millimeters in limb leads.
Major Takeaway
ECG paper has large squares with thick lines; inside each are 25 smaller squares with thinner lines. Horizontally, each small square represents 0.04 seconds. Vertically, each small square represents 0.1 millivolts. There are eight main things the nurse should look for on an ECG to ensure everything is normal within each PQRST wave. First, the heart rate can be calculated by counting the number of QRS complexes in six seconds and multiplying by 10. Secondly, the heart rhythm regularity can be assessed by checking the distance between the peaks of two consecutive P waves and two consecutive R waves if the P-P and R-R interval ratios are one. Thirdly, the P wave should be checked to ensure it is present, regular in timing and shape, and that there is one for each QRS complex. Fourth, the PR interval is checked to make sure it is between 0.12 to 0.20 seconds, three to five little boxes. Fifth, the QRS duration should be consistently less than 0.1 seconds, two and a half little boxes. Sixth, the ST segment should not be elevated or depressed by more than one small box. Seventh, the T wave shape should be asymmetric, and height should be less than 5 millimeters in precordial leads and less than 10 millimeters in limb leads. Finally, the QT interval should be less than or equal to half of a cardiac cycle, which can be calculated by measuring the distance between two successive R waves.
Incorrect answer explanations
A.
Rationale: This is not a normal PQRST wave. This ECG tracing reflects a pathological “Q” wave associated with a previous myocardial infarction. The “Q” wave on the tracing is widened and deep. A normal “Q” wave should be 0.03 seconds or less; the “Q” wave on the tracing is more significant than 0.04 seconds.
B.
Rationale: This is not a normal PQRST wave. The ST segment should not be elevated or depressed by more than one small box. The ST depression in this ECG is abnormal and may be associated with myocardial ischemia.
D.
Rationale: This is not a normal PQRST wave. The ECG tracing reflects an abnormal “P” wave associated with right atrial enlargement that occurs with disease processes such as chronic obstructive pulmonary disease (COPD). The amplitude of a normal P wave should be 0.25 millivolts (mV). Vertically, each small square represents 0.1 mV; therefore, the “P” wave in the tracing is 0.5 mV.
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