T waves may be abnormal in the presence of which conditions?

• A. Ischemia or potassium abnormalities (high or low)
• B. Only ischemia
• C. Only hyperkalemia
• D. Always normal

Answer: (A)

T waves reflect ventricular repolarization, and their appearance changes when the heart muscle is stressed or the electrical environment is altered. Ischemia disrupts repolarization, producing T-wave changes such as peaking early and inversion later. Potassium levels strongly affect T waves: high potassium (hyperkalemia) tends to create tall, peaked T waves, while low potassium (hypokalemia) can flatten T waves and bring out U waves and possible inversion. Because T waves can be abnormal in either ischemia or potassium abnormalities, they’re not limited to one cause. The other options are too narrow or incorrect because T waves are not always normal and can be altered by both ischemia and potassium disturbances (high or low).