Which of the following is NOT a common physiologic or pathologic cause of tachycardia?

• A. Anemia
• B. Fever
• C. Hyperkalemia
• D. Anxiety

Answer: (C)

Tachycardia typically arises when the body needs more cardiac output or when the sympathetic nervous system is activated, boosting heart rate to meet metabolic demands. Anemia lowers the oxygen-carrying capacity of blood, so the heart beats faster to deliver sufficient oxygen to tissues. Fever increases metabolic rate, signaling the heart to beat faster to supply tissues with more energy. Anxiety triggers a surge of catecholamines that stimulate the heart and raise the rate.

Hyperkalemia, by contrast, mainly disrupts the electrical properties of heart cells, tending to slow conduction and can lead to bradycardia or dangerous conduction blocks rather than speeding the heart up. So it is not a common cause of tachycardia, even though severe hyperkalemia can cause serious rhythm problems.