What heart rate is considered irregular?

An irregular heart rate typically refers to a rhythm that is not consistent or follows an unpredictable pattern. The definition of irregular heart rate can encompass bradycardia (a heart rate below 60 beats per minute) and tachycardia (a heart rate above 100 beats per minute), both of which are mentioned in the first choice.

When a heart rate exceeds 100 beats per minute, it may indicate a rapid heartbeat, which could be caused by factors such as stress, activity, or medical conditions. Conversely, a heart rate below 60 beats per minute may signal an abnormality as well, especially if it leads to symptoms like dizziness or fatigue. Both extremes point to irregularities in heart rhythm, thus falling under the classification of irregular heart rate.

The other options are defined with specific ranges or numbers that do not reflect varying degrees of irregularity. For instance, a heart rate between 60 to 100 beats per minute is generally considered normal and regular, while rates such as 40 beats per minute or a constant 70 beats per minute suggest stability rather than irregularity. Therefore, the first choice effectively covers the range of potential heart rates that could be classified as irregular, making it the accurate answer for this question.