Normal sinus rhythm is characterized by which of the following?

Normal sinus rhythm is characterized by a heart rate that ranges from 60 to 100 beats per minute. This interval represents the typical firing rate of the sinoatrial (SA) node, which is responsible for initiating the electrical impulses that regulate the heartbeat in a healthy heart. Within this range, the heart maintains an efficient rhythm conducive to effective blood circulation throughout the body.

A heart rate below 60 beats per minute is classified as bradycardia, which can indicate an issue with the heart's ability to maintain an adequate rate to meet the body's demands. Conversely, a heart rate above 100 beats per minute suggests tachycardia, which may occur under stress, illness, or other physiological circumstances that require an increased heart rate. Therefore, the choice that aligns with the definition of normal sinus rhythm is a heart rate of 60 to 100 beats per minute.