This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Medicine
Which of the following best describes the effect of calcium ions on the myocardium? 
Select and explain. 
A. positively inotropic, B. negatively inotropic, C. positively chronotropic, D. negatively chronotropic
A: positively inotropic
Answer: A: positively inotropic 
Explanation: Positively inotropic is the best description of the effect of calcium ions on the myocardium.Calcium plays a role in excitation-contraction coupling, and in possible drug effects and heart failure.