Cardiac Medicine Certification (CMC) Practice Exam

What may be an underlying cause of symptomatic bradycardia?

1. Excessive hydration

2. Increased physical activity

3. Electrolyte imbalance

4. Severe dehydration

The correct answer is: Electrolyte imbalance

Symptomatic bradycardia refers to a slower than normal heart rate that can lead to symptoms such as fatigue, dizziness, or fainting. Electrolyte imbalances are known to potentially influence the electrical conduction system of the heart, which controls heart rate. Specifically, abnormalities in levels of potassium, calcium, or magnesium can disrupt normal heart rhythm and lead to bradycardia. For example, hyperkalemia (high potassium levels) can cause the heart to slow down significantly and exhibit dangerous rhythm abnormalities. Therefore, electrolyte imbalances are a plausible underlying cause of symptomatic bradycardia. Other options, while they may impact heart function, do not typically lead to bradycardia directly in the way that electrolyte imbalances do. Excessive hydration might lead to changes in body fluid levels, but it doesn’t typically lead to a direct decrease in heart rate. Increased physical activity usually elevates heart rate rather than causing bradycardia. Severe dehydration can result in various cardiovascular changes, but it more often leads to tachycardia (increased heart rate) as the body compensates for decreased blood volume. Thus, electrolyte imbalance stands out as a classic underlying cause of symptomatic bradycardia.