Left axis deviation criteria: which statement best describes this condition on the ECG?

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Multiple Choice

Left axis deviation criteria: which statement best describes this condition on the ECG?

Left axis deviation is about the direction of the heart’s mean QRS axis in the frontal plane. When the depolarization vector points more to the left (roughly between -30° and -90°), the QRS is typically positive in lead I and negative in lead aVF. This pattern—QRS directed toward the left and away from the inferior leads—best matches left axis deviation. The described range (-30° to -90°) with a positive QRS in lead I and a negative QRS in aVF is the classic ECG signature of LAD. Other patterns either stay within the normal axis range or indicate a rightward shift, which have different lead polarities (for example, a rightward axis tends to give different results in lead I and aVF) and thus do not describe LAD.

Left axis deviation is about the direction of the heart’s mean QRS axis in the frontal plane. When the depolarization vector points more to the left (roughly between -30° and -90°), the QRS is typically positive in lead I and negative in lead aVF. This pattern—QRS directed toward the left and away from the inferior leads—best matches left axis deviation. The described range (-30° to -90°) with a positive QRS in lead I and a negative QRS in aVF is the classic ECG signature of LAD. Other patterns either stay within the normal axis range or indicate a rightward shift, which have different lead polarities (for example, a rightward axis tends to give different results in lead I and aVF) and thus do not describe LAD.

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