Coronary arteries normally dilate to increase blood flow, but fixed lesions can impede this dilation, leading to symptoms of stable angina.

“So the way the coronaries work physiologically is that they augment blood flow by dilating. So it's a different physiology than most other vascular beds. So it's part of the reason these drugs like adenosine work is that they dilate the coronary. That's why people are told to take nitroglycerin if they're having chest pain. That's right. But the problem is if you've got a fixed lesion there that's full of a calcified plaque with a bunch of different lipids and stuff in there, you can't really dilate.”