Question

A left axis deviation of \(-30^\circ\) to \(-60^\circ\) on the ECG is seen in?

• A. Left ventricular hypertrophy
• B. Right ventricular hypertrophy
• C. Aortic stenosis
• D. Left atrial enlargement

Hint:

Axis more negative than \(-30^\circ\) points to the left ventricle being enlarged.

Answer 1

The Correct Option is A

Step 1: The normal QRS axis on the ECG ranges from about \(-30^\circ\) to \(+90^\circ\). An axis more negative than \(-30^\circ\) is called left axis deviation, and an axis more positive than \(+100^\circ\) is right axis deviation.

Step 2: A left axis deviation in the \(-30^\circ\) to \(-60^\circ\) range reflects a leftward and superior shift of the mean QRS vector, which occurs when the left ventricular mass increases.

Step 3: Left ventricular hypertrophy is therefore a recognized cause, along with left anterior fascicular block and inferior myocardial infarction.

Step 4: The distractors are wrong because right ventricular hypertrophy typically causes right axis deviation, aortic stenosis affects the LV but is not the direct axis cause asked here, and left atrial enlargement alters the P wave (P mitrale), not the QRS axis.