What condition is suggested by a QRS that is negative in lead I and negative in lead AVF?

What condition is suggested by a QRS that is negative in lead I and negative in lead AVF?

• A. Normal axis
• B. Left axis deviation
• C. Severe right axis deviation
• D. Third-degree heart block

Answer: (C)

A QRS that is negative in lead I and negative in lead AVF indicates a specific orientation of the electrical impulse through the heart. Leads I and AVF are used to determine the electrical axis of the heart. In this case, when both leads show negative deflection, it suggests that the electrical activity is directed away from the normal range, indicating an axis that is displaced towards the right side of the heart.

This pattern is characteristic of severe right axis deviation, which typically occurs in conditions such as right ventricular hypertrophy or other forms of right heart strain. These conditions result in an altered electrical orientation because the heart is positioned or functioning abnormally, leading to a negative QRS complex in both of these leads.

In contrast, a normal axis would show positive QRS complexes in both lead I and lead AVF. Likewise, left axis deviation would show a positive deflection in lead I coupled with a negative or isoelectric in lead AVF, and third-degree heart block typically presents with distinctive wide and unrelated QRS complexes rather than a consistent axis deviation pattern. Thus, the readings in this scenario accurately indicate severe right axis deviation as the correct interpretation.