What effect does hyperkalemia have on cardiac function?

• A. It increases heart rate.
• B. It can cause bradycardia.
• C. It stabilizes cardiac rhythm.
• D. It increases automaticity.

Answer: (B)

Hyperkalemia, which refers to an elevated level of potassium in the bloodstream, has a significant impact on cardiac function, primarily influencing the heart's electrical activity. One of the most critical effects of hyperkalemia is the potential for bradycardia, which is a slower than normal heart rate.

The primary reason for this effect stems from the way potassium ions influence the resting membrane potential of cardiac cells. Elevated potassium levels can lead to a decrease in the membrane potential, making cardiac cells less excitable. As a result, the heart's pacemaker cells in the sinoatrial node may become less effective at initiating impulses, leading to a slower heart rate, or bradycardia. Additionally, hyperkalemia interferes with the conduction of electrical impulses along the heart's conduction pathways, further contributing to this slowing of heart activity.

In contrast to bradycardia, other options do not accurately reflect the physiological response to hyperkalemia. For instance, an increase in heart rate or automaticity would typically require enhanced excitability or depolarization of cardiac cells, which is not aligned with the effects of excess potassium. The statement about stabilization of cardiac rhythm is also not accurate, as hyperkalemia often leads to arrhythmias rather than stabilization