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Understanding Heart Attacks

The first question most people ask when told they have Coronary Artery Disease is "How much of a blockage do I have in my arteries?" Most of us think an 80% blockage is more dangerous than a 30% blockage. In fact, the newest research shows this is not necessarily true.

The vast majority of heart attacks happen in arteries that are less than 50% blocked and are not due to obstruction by the plaque itself.

What is Plaque?

Although the names are similar, coronary artery plaque has nothing to do with the plaque that is present on your teeth. In the coronary arteries, plaque is another name for atherosclerosis, the process that gradually blocks flow through the artery like corrosion in a pipe.

From early childhood onwards, the walls of your arteries start to change. The earliest change is the deposition of cholesterol into the arterial wall to form a "fatty streak". These fatty streaks are often present in the teen years. Over subsequent years, the fatty streak accumulates more cholesterol as well as inflammatory cells, such as macrophages ( a type of white blood cell), fibroblasts (which secrete connective tissue proteins) and muscle cells. Over time, the fatty streak is transformed into a "plaque". As the plaque grows it gradually thickens and can start to intrude into the center of the artery, ultimately impeding blood flow.

By the time a plaque is detectable it has a complex structure including a fibrous cover (or "cap"), a gelatinous core filled with cholesterol and other lipids, and areas of calcium deposits ("calcification").

Heart Attacks and Plaque Rupture

It turns out that heart attacks are not the result of gradual narrowing of an artery to the point that it eventually completely closes off. Instead, the thin cap that covers even a small plaque can split open, exposing the inside of the plaque to the bloodstream. The contents of the plaque activate the platelets in the blood, causing a clot to form over the ruptured cap. Within minutes, that clot can become large enough to completely block the artery.

So, heart attacks are usually the result of a blood clot that forms over a small, ruptured plaque and are not due to a blockage from the plaque itself.

This also means that the invasive procedures physicians traditionally use on more severe blockages (such as angioplasty, stents and bypass surgery) are not effective at preventing heart attacks. These procedures are generally done only at the spots where there is a high-level blockage (70% or more) in an artery. These blockages can cause symptoms, such as exertional chest or angina, and stents or bypass surgery can be very effective at relieving those symptoms. The problem is that an artery with a high-level blockage is very likely to have multiple smaller plaques throughout the rest of the artery. Stents and bypass surgery do nothing to prevent rupture of those plaques. (Learn More About the Limitations of Stents and By-Pass Surgery)

Preventing Heart Attacks

Preventing heart attacks requires treating the entire coronary arterial system. The latest research shows that intensive, non-invasive treatment can be effective at stopping, or even reversing, the formation of plaque and preventing plaque rupture.

By limiting or stopping the progression of plaque, the risk of a heart attack can be dramatically reduced.

In a recently published study , 495 patients were followed for 3 years with EBT Heart Scans to measure the progression of plaque in their coronary arteries. Ninety-five percent of the heart attacks occurred in those patients who had more than a 15% annual increase in their EBT Calcium Scores on the scan.

New research into managing cholesterol levels has also shown promise The REVERSAL trial, presented in November, 2003, showed that more intensive treatment can reverse the build-up of plaque in the coronary arteries. The PROVE-IT trial, presented in April, 2004, demonstrated a 16% reduction in deaths due to heart attacks in patients who were treated with aggressive cholesterol-lowering therapy.

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