Diuretic-induced deficiencies in potassium and magnesium can have significant implications for patients with cardiovascular disease. Hypokalemia, found in up to 50 percent of patients receiving thiazide therapy, is associated with a greater frequency of serious arrhythmias and increased mortality in patients with acute myocardial infarction. Hypomagnesemia has been identified in 42 percent of patients with hypokalemia, and below normal muscle magnesium levels have been found in 43 percent of congestive heart failure patients receiving diuretics. Magnesium is important for maintenance of cell potassium, and infusions of magnesium alone have increased muscle potassium and magnesium levels and significantly decreased the frequency of ventricular ectopic beats. It has been shown that both potassium and magnesium are conserved by potassium-sparing agents. Because serum and tissue magnesium levels are not correlated and correlations for potassium levels are weak, prevention of these electrolyte abnormalities is advised.