How Cholesterol Triggers Heart Attacks

Researchers know high cholesterol levels in the blood lead to cholesterol deposits in the arteries. Over time, these cholesterol deposits are believed to somehow promote heart attacks, strokes, and other cardiovascular events. However, the mechanism by which cholesterol deposits can trigger plaque rupture and a heart attack has remained a bit of a mystery.

In recent years, growing attention has been placed on inflammation in diseased arteries as the trigger for plaque rupture and clot formation. It is known that in some people plaques rupture with relatively little inflammation and in other cases inflammation plays a major role.A study in the September 2005 issue of Clinical Cardiology sheds new light on the role that cholesterol deposits appear to be playing in triggering plaque rupture.Cardiologist George Abela’s work, at Michigan State University, shows that as cholesterol goes from a liquid to a solid, it expands in volume by about 45%.Dr. Abela found that once the cholesterol starts to crystallize, it takes only a few minutes to go from a liquid to solid state. If a large cholesterol deposit in the artery wall crystallizes, this expansion could rupture the fibrous cap surrounding it. Once the plaque ruptures, the blood is exposed to dead and dying cells that release chemical agents that trigger a blood clot that stops blood flow.However, when the cholesterol deposits in the artery wall are smaller, Dr. Abela found the cholesterol crystals can penetrate thin membranes. He believes these smaller crystals could do enough damage to lead to the breakdown of the fibrous cap separating the plaque’s contents from the blood flowing through the artery.If Dr. Abela is correct, reducing the amount of cholesterol in the artery walls should help reduce chances for crystallization, inflammation, and plaque rupture. Cholesterol in the arteries comes from dietary cholesterol as well as cholesterol made by the liver in response to diets higher in saturated fat and trans fats and low in fiber.By James J. Kenney, PhD, RD, FACN.