Which leads are expected to have isoelectric QRS complexes?

Which leads are expected to have isoelectric QRS complexes?

• A. V1 and V2
• B. V5 and V6
• C. V3 and V4
• D. I and II

Answer: (C)

The correct leads that are expected to demonstrate isoelectric QRS complexes are V3 and V4. In the context of an electrocardiogram (EKG), an isoelectric QRS complex implies that the electrical activity of the heart is being recorded in a state where upward and downward deflections are equal, resulting in a flat line at the baseline.

Leads V3 and V4 are positioned centrally on the chest, capturing the electrical activity from the heart in a way that can lead to this isoelectric phenomenon, particularly when the heart's axis aligns in a manner that results in balanced electrical forces. The positioning of these leads allows for a clear depiction of the heart's electrical conduction through the anteroseptal wall, which can reveal periods where there is less electrical activity in relation to other leads, resulting in the presence of isoelectric complexes.

Understanding isoelectric segments is crucial for diagnosing various cardiac conditions, and recognizing which leads typically reflect this phenomenon helps in accurately interpreting the EKG and assessing the heart's function.