Define bradycardia and tachycardia.

• A. Bradycardia is a fast heart rate
• B. Tachycardia is a slow heart rate
• C. Bradycardia is a heart rate greater than 100 bpm
• D. Bradycardia is an unusually slow heart rate (typically <60 bpm); Tachycardia is a fast heart rate (typically >100 bpm)

Answer: (D)

Bradycardia and tachycardia describe slow and fast heart rates, respectively. Bradycardia is an unusually slow heart rate, typically less than 60 beats per minute. Tachycardia is a fast heart rate, typically greater than 100 beats per minute. In adults, a normal resting rate is about 60–100 bpm, so these thresholds mark departures from normal. Some people, such as highly trained athletes, may have bradycardia without symptoms due to a larger stroke volume. Tachycardia can arise from factors like fever, dehydration, anxiety, anemia, or heart problems and may require evaluation if persistent or symptomatic. This definition pair precisely conveys both terms with clear, widely used thresholds, making it the best description. The other statements either swap the terms or use the wrong direction for the thresholds.