A 12-lead ECG can reveal conduction abnormalities such as which of the following?

• A. Branches of conduction system blocked
• B. Entire electrical flow is slightly off kilter
• C. Metabolic or chemical abnormalities
• D. All of the above

Answer: (D)

A 12-lead ECG can reveal a range of electrical abnormalities, not just focal blocks in the heart’s conduction pathways but also global changes in how the heart’s impulse spreads, and even signs of metabolic or electrolyte disturbances that affect conduction and repolarization. When a branch of the conduction system is blocked, the ECG shows characteristic bundle-branch block patterns with a widened QRS and distinct V1/V6 changes. If the overall electrical flow is off kilter, the QRS axis shifts, producing an abnormal frontal-plane axis or other global pattern. Metabolic or chemical disturbances—such as electrolyte imbalances—alter membrane potentials and conduction, producing recognizable changes like tall or peaked T waves in hyperkalemia, flattened T waves and U waves in hypokalemia, or changes in QT interval with calcium or magnesium disturbances. Because the ECG can reflect all of these different issues, choosing all of the above is the best answer.