What will an anterior hemiblock look like on an EKG?

What will an anterior hemiblock look like on an EKG?

• A. Widened QRS complexes with a Q wave in lead II
• B. Normal or slightly widened QRS complexes with a deep S wave in lead III
• C. Normal QRS with ST elevation in leads V1 and V2
• D. Inverted T waves in leads V1 and V2

Answer: (B)

An anterior hemiblock, also known as a left anterior fascicular block, manifests on an EKG primarily through characteristic patterns observed in the leads. The key feature of an anterior hemiblock is the presence of a normal or slightly widened QRS complex, which indicates that conduction through the ventricles is generally intact, although there’s a delay in conduction due to the fascicular block.

In addition, one of the most significant findings is the presence of a deep S wave in lead III. This occurs because the electrical conduction is altered, affecting the depolarization vector, which typically causes a deviation towards the left anterior side of the heart, hence the prominent S wave in lead III. Consequently, this pattern helps to diagnose the block as it directly reflects the left axis deviation that occurs due to the anterior hemiblock.

Other options present patterns that do not correspond with the typical findings of an anterior hemiblock. For instance, widened QRS complexes with a Q wave in lead II would suggest more complex conduction issues or other cardiac conditions. Similarly, ST elevation in leads V1 and V2 would generally indicate ischemic changes rather than a simple fascicular block, and inverted T waves in these leads might suggest different pathophysiological processes.