Answer: Magnesium, potassium and calcium
Explanation: This is evident in the roles these cations play at the intercellular levels on muscle contractions. Potassium is vital to the contractions of the heart and skeletal muscles, Calcium mediates muscular contractions and regulates the activity of the CNS, Magnesium regulates the Flux of calcium. So it is evident that any change in their concentrations would significantly affect the activities of the heart muscles especially.