ECG: electrical axis: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · ECG: electrical axis

Sample item

In a 6-year-old with long-standing pulmonary stenosis, the ECG shows a predominantly negative QRS in lead I and a positive QRS in lead aVF. What does this indicate?

ALeft axis deviation, as seen in left anterior fascicular blockBExtreme axis deviation, as seen in ventricular rhythmsCNormal axis, as in a healthy childDRight axis deviation, as seen in right ventricular hypertrophy

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Right axis deviation, as seen in right ventricular hypertrophy

A negative QRS in lead I with a positive QRS in aVF places the frontal plane axis between +90 and +180 degrees, which is right axis deviation. It is seen in right ventricular hypertrophy such as in pulmonary stenosis or pulmonary hypertension, and in lateral infarction. A positive lead I and aVF indicates a normal axis.

Option by option

A. Left axis deviation, as seen in left anterior fascicular block
Left axis deviation shows a positive lead I and a negative aVF.
B. Extreme axis deviation, as seen in ventricular rhythms
Extreme axis shows a negative QRS in both leads I and aVF.
C. Normal axis, as in a healthy child
A normal axis shows a positive QRS in both lead I and aVF.
D. Right axis deviation, as seen in right ventricular hypertrophy (correct)
Correct. Negative lead I with positive aVF is right axis deviation.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, Right axis deviation, as seen in right ventricular hypertrophy. A negative QRS in lead I with a positive QRS in aVF places the frontal plane axis between +90 and +180 degrees, which is right axis deviation.

Why is "Left axis deviation, as seen in left anterior fascicular block" not the answer?

Left axis deviation shows a positive lead I and a negative aVF.

Why is "Extreme axis deviation, as seen in ventricular rhythms" not the answer?

Extreme axis shows a negative QRS in both leads I and aVF.

Why is "Normal axis, as in a healthy child" not the answer?

A normal axis shows a positive QRS in both lead I and aVF.

What concept does this question test?

It tests ECG: electrical axis in Physiology. It is seen in right ventricular hypertrophy such as in pulmonary stenosis or pulmonary hypertension, and in lateral infarction. A positive lead I and aVF indicates a normal axis.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study ECG: electrical axis?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.