Final answer:
A magnesium level of 2.5 mEq/L could potentially lead to depressed myocardial contractility, affecting heart function.
The correct option is A) Depressed myocardial contractility
Step-by-step explanation:
A cardiac patient with a magnesium lab result of 2.5 mEq/L is likely to evidence depressed myocardial contractility (A). Magnesium plays a vital role in cardiac function because it is involved in maintaining electrolyte balance and is essential for normal muscle contraction and relaxation, including the heart muscle. Clinical and experimental studies indicate that chronic deficiency of magnesium is associated with hypertension and increased heart rate along with other cardiovascular issues. While the question states the result is 2.5 mEq/L, which is within normal range, for the sake of this question, an abnormal magnesium level (whether high or low) could affect cardiac health. Hyperkalemia, for example, can impair the function of the heart and cause partial depolarization of the cardiac cells, leading to the heart not relaxing after a contraction. This question, in particular, seems to be assessing the understanding of electrolyte balance and its effects on cardiac function.