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
A patient having prinzmetal angina is started with ISMN. Patient got symptomatic relief from angina. What is the MOA? 
Select and explain. 
A. Endothelium independent coronary vasodilatation, B. Reduced cardiac contractility, C. Increased left ventricular end diastolic volume, D. Decreased diastolic perfusion pressure
A: Endothelium independent coronary vasodilatation
Answer: A: Endothelium independent coronary vasodilatation 
Explanation: ANS. A# Important points on nitrates1. All nitrates have high FPM metabolism except ISMN (Isosorbide mononitrate)2. Skin rashes are maximum with Pentaerythritol tetranitrate3. Nitrates used in acute attack: NTG and ISDN (Isosorbide dinitrite)