This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Arrhythmias, Subject name: Medicine
Heart block is seen in - 
Select and explain. 
A. Hypermagensemia, B. Hypomagnesemia, C. Hypernatremia, D. Hypocalcemia
A: Hypermagensemia
Answer: A: Hypermagensemia 
Explanation: Ans. is i.e., Hypermagnesemia o Hypermagnesemia slows the heart and leads to heart block.o Hypomagesemia leads to cardiac arrhythmias like SVT and VT.HypermagnesemiaHypomagnesemiaInhibits PTH releaseInhibits calcium reabsorptionResistance to PTHDecreased production of vitamin D3Vasodilation : HypotensionTetanyNeuromuscular blockade : DTK inhibitedVertigo/ataxia'nystagmusRespiratory' failure : Decreased respiratory rateDepression-psychosisBowel sounds reduced'ileus Pupils dilated Heart rate decreasedHeart rate increasedECG : PR, qRS and QT prolongationPR and QT prolongation with T wave inversion