What is suggested when the QRS is positive in lead I and negative in lead AVF?

What is suggested when the QRS is positive in lead I and negative in lead AVF?

• A. No axis deviation
• B. Left axis deviation
• C. Normal axis
• D. Left anterior fascicular block

Answer: (B)

When the QRS complex is positive in lead I and negative in lead aVF, it particularly suggests left axis deviation. In a normal axis, we typically expect the QRS complexes to be positive in both lead I and lead aVF, or positive in lead I with a flat or slightly negative aspect in lead aVF indicating a more neutral axis position.

Left axis deviation commonly occurs when the electrical axis moves towards the left side of the heart, which can be visualized through the relationship of leads on the EKG. Lead I being positive means the heart's electrical activity is directed towards the left side, while a negative QRS in aVF indicates the vector is directed upward—confirming a leftward shift.

This pattern of leads aligns with various cardiac conditions, such as left ventricular hypertrophy or left bundle branch block, which might alter the QRS vector direction. Thus, this combination of positive and negative QRS deflections unequivocally indicates left axis deviation, validating the interpretation of the EKG findings in the context of axis determination.