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: Pharmacology
[{'content': "A patient of prinzmetal's angina is started on isosorbide mononitrate. What is the mechanism of action of nitrates in this condition? \nSelect and explain. \nA. Reduced cardiac contractility, B. Increased left ventricular end diastolic volume, C. Decreased diastolic perfusion pressure, D. Endothelium independent coronary vasodilation", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (D) Endothelium independent coronary vasodilation(Ref: KDT 7th/e p541)Predominant mechanism of action of nitrates in angina:*In Classical angina: Decrease in preload*In Variant angina: Coronary vasodilation', 'role': 'assistant'}]