This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Cardiotoxicity of bupivacaine - \nSelect and explain. \nA. Depressed pacemaker activity, B. Toxic compound damaging myocardial cells, C. Depressed neural control on hea, D. Vascular thrombosis and Myocardial ischemia', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Depressed pacemaker activity o Local anaesthetics block cardiac sodium channels and thus depress abnormal cardiac pacemaker activity, excitability, and conduction. At extremely high concentrations, local anaesthetics can also block calcium channels.", 'role': 'assistant'}]