What is classified as atypical tachycardia?

Atypical tachycardia is characterized by elevated heart rates that fall outside of the normal range for a specific duration. When considering the options, it is essential to focus on both the heart rate and the duration to identify what constitutes atypical.

A heart rate of 160 beats per minute maintained over a period of 30 to 80 minutes reflects a significant and sustained increase. This duration indicates that the tachycardia is not only present but prolonged, which could signal underlying issues that require monitoring or intervention. This length of time, combined with a heart rate that is clearly elevated, fits the criteria for atypical tachycardia more definitively than other time and rate combinations.

In contrast, other options present either a lower heart rate or shorter durations that would not typically indicate atypical tachycardia. The sustained heart rate of 160 bpm for 30 to 80 minutes aligns well with common diagnostic criteria used in fetal assessments, marking it as a more serious concern than the other scenarios presented.