Which heart rate is indicative of beta-blocker overdose?

In the context of beta-blocker overdose, a heart rate of 35 beats per minute is indicative of bradycardia, which is a significant slowing of the heart rate. Beta-blockers are known to inhibit the sympathetic nervous system's effect on the heart, leading to a decrease in heart rate. In cases of overdose, this effect can be exaggerated, causing the heart rate to drop substantially below normal physiological levels, typically defined as under 60 beats per minute.

Bradycardia resulting from beta-blocker overdose can lead to decreased cardiac output and may be associated with more severe symptoms such as hypotension and altered mental status. Therefore, a heart rate of 35 beats per minute is a critical sign that warrants immediate medical attention, given that it is significantly lower than the normal resting heart rate range, which is generally between 60 and 100 beats per minute in adults.

In contrast, heart rates such as 60, 75, or 80 beats per minute, while slightly on the lower end of the normal range, do not suggest the same level of concern as the markedly low rate of 35 beats per minute, which is characteristic of overdose scenarios.