What is a common cause of sinus bradycardia on an EKG?

Sinus bradycardia refers to a slower than normal heart rate, characterized by a heart rate of less than 60 beats per minute, while still maintaining a regular rhythm originating from the sinus node. Increased vagal tone and the effects of certain medications are well-established causes of this condition.

When the vagus nerve, which promotes the 'rest and digest' responses, is stimulated, it can result in a decreased heart rate. This is often seen during situations that activate the vagus nerve, such as during certain activities or in response to certain physiological conditions. Additionally, various medications, particularly beta-blockers, digoxin, and certain antiarrhythmics, can also enhance vagal tone or mimic its effects, leading to a decreased heart rate.

Understanding the impact of vagal tone is crucial, as it illustrates the balance between the autonomic nervous system's influences on heart function. Low heart rates caused by increased vagal activity are usually benign, particularly in well-conditioned athletes or in certain resting states.

In contrast, factors like dehydration, increased exercise, and electrolyte imbalances may affect heart rate regulation but are less directly linked to the mechanisms causing bradycardia from enhanced vagal activity or medication effects. These other factors typically lead