22 March 2004

 

How Could the 40 Year Old Jogger Who Just Had a Physical Get a Heart Attack? Heart Attacks Happen Even in People Who Don't Have Already Narrow Arteries: Cholesterol Lowering More Important Than Ever

Cholesterol Lowering Drugs Seem to Lower Number of Coronary Events

A 40 year old man, a jogger actually, is standing at a bus stop when he suddenly has a heart attack. It doesn't seem to add up. Here's a man who gets regular check ups and exercises and yet he has a heart attack.

How Could the Jogger Who Just Had a Check Up Get a Heart Attack?

What causes a heart attack? It's so obvious! Everyone thinks they know the answer and everyone certainly thinks that their doctor knows the answer. But actually it's not obvious at all. For years, doctors have been doing tests called angiograms to look for areas of narrowing and blockage in the arteries of the heart. At the same time studies have demonstrated that many people who don't have narrowing of an artery can have a blockage develop all of a sudden in that artery with a resulting heart attack. Certainly if you find a very narrow or almost totally blocked artery (an occlusion) it makes sense to open up the artery increasing the diameter of the lumen so that more blood can flow.

When a person has a heart attack what is usually happening is that there has been a sudden blockage of one of the arteries that feed the heart. These arteries, the coronary arteries, supply the oxygen rich blood that fuels the heart muscle itself letting the heart pump blood to the rest of the body. The treatment at the time of the heart attack is to remove the blockage as fast as possible using clot busting drugs or an angioplasty (using a mechanical device) to open the blocked artery. Time is of the essence in that situation.

The Million Dollar Question: What Causes a Heart Attack?

However, the million dollar question is what is the reason that blockages occur in the first place? Ask most people, even most doctors, and they will say something to the effect that the artery becomes narrower over time with deposits of cholesterol and fatty sludge. So you have an already narrowed artery which suddenly becomes blocked as with a blood clot from the artery wall and that leads to total blockage viz. a heart attack.

Inflammation Tied to Cholesterol Leading to Heart Attack

Actually evidence has been accumulating for years that the reason for many blockages is that cholesterol is deposited in the lining of the artery and triggers an inflammatory cascade in the lining of the artery. That inflammation builds up in the lining and is covered by a cap. When that cap breaks, the contents beneath the cap, cause a blood clot to form in the blood that is passing by in the lumen of the artery and voila it's a blockage. Statistical analysis has revealed that regular aspirin usage lowers the chance of a heart attack. Why? The most prevalent explanation is that aspirin interferes with clot formation through it's effect on bleeding. Perhaps inflammation is also involved. As a matter of fact doctors have been wondering if other drugs that seem to have a positive impact on the heart, such as ACE inhibitor blood pressue pills are acting on inflammation.

According to Harvard Doctor, Pathologists Have Demonstrated That Cap in Inflammatory Plaque Breaks Off Leading to Blood Clot that Blocks the Artery

In New Studies Question Value of Opening Arteries in the New York Times, Gina Kolata discusses this issue and the controversy that surrounds it in the world of cardiology. Actually, it's not new, despite the headline and Purple Medical Blog has discussed this issue before. In the classic explanation of the dangers of high cholesterol, high cholesterol leads to the narrowing of the coronary arteries and a plaque may break off and block or occlude the artery. The result is little or no blood flow to the part of the heart being supplied by that artery and a heart attack. As Dr. Peter Libby points out "sometimes a plaque grows so large that it virtually halts the blood flow in an artery and generates a heart attack or stroke. (he means a stroke caused by a blockage, a thrombotic stroke, but there's also another kind called a hemorrhagic stroke which is due to bleeding) Yet only 15% of heart attacks happen in this way. By carefully examining vessel walls of people who died from heart attacks, pathologists have demonstrated that most attacks occur after a plaque's fibrous cap breaks open" attracting a blood clot that leads to the blockage of the artery. See the fascinating and instructive article by Dr. Libby Atherosclerosis The New View.

Cholesterol Lowering Drugs Seem To Decrease Number of Coronary Events

Dr. Libby, a professor at Harvard Medical School, has pointed out that the cholesterol lowering drugs seem to decrease the number of coronary events such as heart attacks even though angiograms don't necessarily show a decrease in the stenosis or narrowing of the artery. See the more technical article Molecular Bases of the Acute Coronary Syndromes
 

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