In my previous blog, How do the Majority of Heart Attacks Occur? Dr. Caldwell Esselstyn Jr. demonstrates how the greatest percentage of heart attacks (87.5%) occur when newly formed plaques on the inside of our arteries rupture, causing a clot to form, and thus blocking the flow of blood. This little-known fact comes as a surprise to most people since heart arteries narrowed by atherosclerotic blockages are usually blamed. However, coronary arteries with significant blockages account for only a small percentage (approximately 12.5%) of heart attacks. It helps to think of cholesterol plaques as being Arterial Acne, or "inflamed pockets of pus." When thought of this way, we can grasp a better understanding of how plaques rupture -- spilling their contents into the bloodstream, causing an inflammatory reaction and subsequent clot. Referring to a study conducted by a team led by George Abela, chief of the cardiology division in MSU’s College of Human Medicine, Dr. Michael Greger demonstrates this mechanism in the video below.
The study was based on the findings of autopsies performed on individuals that suffered a fatal heart attack as well as those that died from other causes. The atherosclerotic plaque from patients that died from acute heart attacks contained cholesterol crystals which had burst through the plaque membrane and protruded significantly into the middle of the artery whereas perforating crystals were not found in the arteries of those that had severe atherosclerosis, but died of other (non-cardiac) causes. Because cholesterol has specific crystal characteristics, this finding led researchers to question whether cholesterol could become so supersaturated, that it could expand and crystallize (much like sugar turns into rock candy), thus causing the plaque membrane to rupture.
In order to test this hypothesis, twelve test tubes were filled with a supersaturated solution of cholesterol and capped with a thin membrane representing the cap covering atherosclerotic cholesterol plaques. Any physical transformation of the liquid state to a solid crystal state could then be observed. Just like water expands as it freezes, the liquid state of cholesterol differs from the crystalized solid state. Indeed, researchers watched as the supersaturated liquid cholesterol converted to a crystalized solid state. The crystalized cholesterol expanded and shot out of the tops of the test tubes, tearing the membranes. Dr. Greger notes in his video that "as cholesterol crystallized, the peak volume can increase rapidly by up to 45% within minutes, and sharp-tipped crystals can cut through and tear membranes, suggesting that the crystallization of supersaturated cholesterol in atherosclerotic plaques can induce rupture."
This study provided evidence that higher cholesterol deposits "alter the physical state of cholesterol from a liquid to a solid crystal state." Once crystallization begins, it "proceeds rapidly and forcibly" which can tear, stretch and rupture the fibrous membrane covering plaque deposits, resulting in plaque rupture and a "higher frequency and severity of artery damage, leading to acute cardiac events."
Microscopic views of the crystals revealed sharp, jagged, cutting, needle-like projections as seen in the cover photo above. These jagged edges not only tear and weaken the fibrous cap (decreasing plaque stability), they can break through the membrane and travel farther down the blood vessel, causing damage to the endothelial lining. This demonstration, along with Dr. Esselstyn's illustration of how the force of the blood pumping with each heartbeat can easily tear the cap from these fragile plaques, offers an easy-to-understand explanation of the sequence of events which triggers a heart attack or stroke.
This may explain one reason why consuming a diet based on whole natural plant foods lowers the risk of fatal heart attacks -- it pulls cholesterol out of the artery walls, decreasing the risk of the formation of cholesterol crystals which rupture the plaques. For more information, you may also enjoy reading my article, Who Has Heart Disease? Everyone!
Image Credit - Cholesterol Crystals Cause Mechanical Damage to Biological Membranes:
A Proposed Mechanism of Plaque Rupture and Erosion Leading to Arterial Thrombosis
Video Credit - Cholesterol Crystals may Tear Though our Artery Lining, NutritionFacts.org