Which of the following is a known cause of triggered activity?

Triggered activity is a phenomenon often seen in cardiac electrophysiology, where an abnormal electrical impulse is produced in the heart. It is typically associated with conditions that alter the ionic environment or the resting membrane potential of cardiac cells. Hypomagnesemia, which refers to low levels of magnesium in the blood, can lead to the development of triggered activity. Magnesium plays a crucial role in cardiac cellular function, and its deficiency can cause an increased excitability of cardiac cells, leading to abnormal electrical discharges.

In contrast, hypercalcemia affects cardiac contractility and can increase the threshold for action potential generation but is more associated with other types of arrhythmias. Hyperlipidemia primarily relates to lipid metabolism and does not have a direct impact on cardiac electrical activity in the same way that magnesium levels do. Hyponatremia involves low sodium levels, which can influence overall fluid balance and cell function, but it is not a primary cause of triggered activity.

Thus, hypomagnesemia's specific role in facilitating triggered activity makes it the correct choice in this scenario.