 In my video, Arterial Acne, I described atherosclerotic plaques as inflamed pockets of pus. Our coronary artery start out healthy as kids, but then the standard American diet, the saturated fat, trans fat, and cholesterol increases the cholesterol in our blood, which accumulates in the artery wall, triggering an inflammatory response. The fatty streak becomes an atherosclerotic plaque, which can then rupture into our artery and blood clot and form, cutting off blood flow to a part of our heart, which can then die and kill us. What causes that final step, the rupture of the plaque? Ten years ago, researchers at Michigan State proposed a mechanism. They noted that when you looked at ruptured plaques from human autopsies of people that died from heart attacks, they're filled with cholesterol crystals protruding out from the plaque. So they wondered if maybe all that cholesterol on the plaque gets so supersaturated that it reaches a point that it crystallizes like sugar water forming rock candy. The growing crystals may then burst the plaque open, so they made a supersaturated solution of cholesterol in a test tube to see if it, when it crystallizes, it would expand. And indeed it did, just like how water expands when it crystallizes into ice. Here's a cholesterol crystal shooting out the top of a test tube. When you look at the tips of the cholesterol crystals under a microscope, they are sharp jagged needles. They placed a thin membrane over the top of the test tube to see if the cholesterol needles would kind of poke through. And indeed, the sharp tips of the cholesterol crystals cut through the membrane. So they showed that as cholesterol crystallized, the peak volume can increase rapidly by up to 45% within minutes. And sharp tip crystals can cut through and tear membranes, suggesting that the crystallization of supersaturated cholesterol in atherosclerotic plaques can induce the rupture that kills us. A test tube is one thing. But can you actually see crystals poking out in autopsy specimens? Yes. Cholesterol crystals piercing the arterial plaque was found in patients who died with heart attacks, acute coronary syndrome. Extensive protrusion of cholesterol crystals into the middle of the artery. What makes us think it was the cholesterol that actually, the crystals that actually burst the plaque? All patients who died of acute heart attacks had perforating cholesterol crystals like this sticking out of their plaques. But no crystals were found perforating the arteries of people who had severe atherosclerosis but died first of other non-cardiac causes. This can explain why dramatically lowering cholesterol levels with diet or drugs can reduce the risk of fatal heart attack by pulling cholesterol out of the artery wall, decreasing the risk of crystallizing these cholesterol needles that may pop the plaque.