Which categories can cause abnormal conduction?

• A. Only functional abnormalities
• B. Functional, anatomical, and chemical abnormalities
• C. Only anatomical abnormalities
• D. Only chemical abnormalities

Answer: (B)

Abnormal conduction can arise from any disturbance that alters how impulse propagation occurs in the heart. If the conduction pathway is structurally altered, such as scar tissue from prior infarction or congenital fiber discontinuities, conduction is physically slowed or blocked. Functional changes, which are often reversible, modify how readily cells depolarize and how quickly they conduct—ischemia, shifts in autonomic tone, temperature changes, or other transient states can slow or block conduction without a fixed structural lesion. Chemical factors, including electrolyte disturbances (like potassium, calcium, or magnesium imbalances) and drug effects that alter ion channel function, also change conduction velocity and refractoriness. These categories are broad and can interact, so all three can contribute to abnormal conduction.