Final answer:
Abnormal levels of potassium can cause cardiac arrhythmias and even death. Hyperkalemia can prevent the heart from relaxing after a contraction, and hypokalemia can lead to arrhythmias.
Step-by-step explanation:
The electrolyte that can cause cardiac arrhythmias and even death when its levels are abnormal is potassium. Potassium plays a crucial role in maintaining the heart's function. Abnormal levels of potassium, known as hyperkalemia (high potassium levels) or hypokalemia (low potassium levels), can seriously affect the heart. Hyperkalemia leads to partial depolarization of the heart muscle, preventing relaxation after contraction, which can cause the heart to stop pumping blood. Similarly, hypokalemia can lead to dangerous arrhythmias, which disrupt the normal rhythm of the heart's contractions.