Sinus Bradycardia is defined by rate.

• A. <60
• B. 60-100
• C. >100
• D. Rate varies

Answer: (A)

Sinus bradycardia is a slow heart rate that originates from the normal sinus node with a regular rhythm. In adults, it is defined as a heart rate below 60 beats per minute, so the description with a rate less than 60 is the correct definition. A rate of 60-100 beats per minute is considered normal resting heart rate, while a rate above 100 is tachycardia. Saying the rate simply varies does not define bradycardia, because the key feature is a distinctly low rate, not variability. Keep in mind that in some healthy individuals like well-trained athletes or during sleep, a rate under 60 can be normal, but the defining threshold remains <60 bpm.