We used to hear coronary heart disease described as “hardening of the arteries”, or atherosclerosis. I pictured this as some kind of clogged drain under an old sink, plugged up with years of disgustingly hard gunk. But it turns out that only about three out of every 10 heart attacks are actually caused by this kind of hardened coronary artery blockage.
The rest of us can blame soft, vulnerable and unstable plaque within the walls of those arteries. This may also help to explain (as I’ve written about here and here) why you can have a “normal” cardiac test one month, and be back in hospital the following month with a heart attack. Here’s how that can sometimes happen, according to experts at the Texas Heart Institute:
“Studies suggest that many people who have heart attacks do not have arteries severely narrowed by plaque. In fact, soft vulnerable plaque may be buried inside the artery wall and may not always bulge out and block the blood flow through the artery.
“This is why researchers began to look at how inflammation affects the arteries, and if inflammation could lead to a heart attack. Inflammation is your body’s natural reaction to an injury. Inflammation can happen anywhere—on the skin, within the body, and even inside the arteries. Scientists are now learning that inflammation can lead to the development of soft or vulnerable plaque. They also found that vulnerable plaque was more than just debris that clogs an artery, but that it was actually filled with different cell types that help with blood clotting.
“What causes vulnerable plaque? Researchers now think that it’s formed in the following way:
- Fat droplets are absorbed by the artery, which causes the release of proteins (called cytokines) that lead to inflammation.
- The cytokines make the artery wall sticky, which attracts immune-system cells (called monocytes).
- The monocytes squeeze into the artery wall. Once inside, they turn into cells called macrophages and begin to soak up fat droplets.
- These fat-filled cells form a plaque with a thin covering.
“When this inflammation is combined with other stresses, such as high blood pressure, it can cause the thin covering over the plaque to crack and bleed, spilling the contents of the vulnerable plaque into the bloodstream. The sticky cytokines on the artery wall capture blood cells (mainly platelets) that rush to the site of injury. When these cells clump together, they can form a clot large enough to block the artery.
“How is vulnerable plaque detected? Patients with this kind of plaque may not feel any symptoms. In the early stages of the process, the change in blood flow may not be detected with standard testing, but researchers are looking at special scanning techniques that may highlight the presence of vulnerable plaque.
“Cardiologists have found that by measuring the level of a substance called C-reactive protein (CRP) in the bloodstream, they might be able to predict a person’s risk of heart attack or stroke. CRP is a marker that doctors use to measure inflammation activity in the body. Two large studies have shown that the higher the CRP levels in the blood, the greater the risk of a heart attack. Researchers also think that obesity and diabetes may be tied to high levels of CRP. And studies are also looking at how your family history and your genes factor into the inflammation process.
“Not all vulnerable plaque ruptures, and researchers at the Texas Heart Institute are looking at ways to determine which vulnerable plaques are most likely to rupture. Some researchers are measuring the temperature of vulnerable plaque. They found that the warmer the plaque, the more likely it will crack or rupture. Researchers have also discovered that vulnerable plaque has a low pH (i.e. more acidic) and that such acidic plaques are more likely to rupture.
“Can vulnerable plaque be prevented? Patients can help to lower their CRP levels in the same ways that they can cut their heart attack risk:
- eat a heart-healthy Mediterranean diet
- quit smoking
- begin an exercise program
- take aspirin
“Medicines like ACE inhibitors (for treating high blood pressure) and aspirin appear to reduce inflammation in the body, which may prevent heart attacks in people who already have high CRP levels. Cholesterol-lowering medicines called statins have been found to lower CRP. Doctors are still studying the use of cholesterol-lowering medicines for this purpose.
“Recent studies have shown that smoking is very dangerous for people who have vulnerable plaque in their arteries. The nicotine in cigarettes directly affects the inflammatory response, causing the release of more cytokines.
“But most doctors agree that heart-healthy habits still play the most important role in reducing your risk of heart attack.”
© 2016 Texas Heart Institute
CAROLYN’S NOTE: The American Heart Association, among others, do NOT recommend the C-reactive protein test for general screening of heart disease. It’s important to remember that CRP levels can also be elevated in any inflammatory condition, so it’s considered a non-specific test for coronary artery disease. For example, higher CRP levels may also be detected in osteomyelitis, rheumatoid arthritis, inflammatory bowel disease, tuberculosis, some cancers (e.g. lymphoma), pneumonia, and even if you’re on birth control pills or in the second half of pregnancy. Talk to your physician for more info.
Q: Are you familiar with the link between inflammation and heart disease?
- Heart attacks: men explode but women erode
- Squishing, burning and implanting your heart troubles away
- Size matters, but not in coronary artery blockages
- Heart attack: is it a clogged pipe or a popped pimple?
- Cardiovascular Diseases in Chronic Inflammatory Disorders – an expert analysis published by the American College of Cardiology of how various inflammatory disease states elevate risk for cardiovascular disease