<prompt> Which of the following statements best explains the action of nitroglycerine on coronary vessels:It mitigates angina pectoris by increasing total coronary flowIt preferentially dilates conducting aeries without affecting resistance aeriolesIt preferentially dilates autoregulatory aerioles without affecting the larger aeriesIt mainly decreases the after load  <response>: Nitrates cause redistribution of blood flow without affecting total coronary flow. Autoregulatory small vessels remain unaffected whereas large conducting vessels are dilated. Nitrates are predominantly venodilators, therefore decrease mainly preload. 