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Why High ‘Good’ Cholesterol Is No Guarantee Against a Heart Attack

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R. Todd Hurst, MD, FACC, FASE - Blogs
By R. Todd Hurst, MD, FACCBoard-certified cardiologistAugust 17, 2018

“You’ll never have a heart attack.” Jane heard this from several doctors over the years. Why? Because Jane had a very high HDL cholesterol level (171 mg/dL). HDL is often referred to as the “good cholesterol” because high levels are considered to be protective against heart attack.

Yet, despite doctors’ reassurances that her HDL would protect her, Jane was still concerned about her heart disease risk. And rightly so.

Jane was 61, and she felt great. She was very active and didn’t have any chest pain or shortness of breath. She wasn’t taking medications, ate well and had never smoked. Her blood pressure and blood sugar numbers were good. Additionally, her LDL cholesterol (the “bad cholesterol”) was quite low (67 mg/dL).

So, why was Jane concerned about her heart risk? Because her mother had had similar cholesterol numbers. And she had a heart attack in her early 60’s.

The Truth About HDL Cholesterol

Although you may have heard that HDL cholesterol is protective against heart disease (hence the designation “good cholesterol”), the reality is that the impact of HDL cholesterol level on heart disease risk is more complex than originally thought.

Of course, you would think that if having low levels of HDL is bad news (associated with higher risk of heart disease), then very high levels of HDL should be good – but that may not actually be the case.

In fact, the opposite may be true.

In my clinical practice, I have had many patients who have very high HDL cholesterol levels (over 100 mg/dL). The vast majority of these patients have been told that they will never have a heart attack, just like Jane. But in my clinical experience, some of these patients in fact have more artery disease than would be expected based on their other risk factors.

More recent research confirms this observation. A study done in post-menopausal women showed that higher HDL cholesterol was associated with an increased risk of plaque buildup in the arteries. Another study in 2016 showed that those with a genetic variation in a specific type of protein had high HDL levels and an 80% increase in coronary heart disease.

The HDL story gets more complicated when we look at the outcome data from medications that raise HDL. For example, long acting niacin, a medication that increases HDL (and lowers LDL), did not decrease heart disease when added to a statin in 2 large trials. Another type of medication that raises HDL level dramatically, called CETP inhibitors, has been tested in several clinical trials and they have generally not been effective in lowering heart disease. In one study, the CETP inhibitor torcetrapib was actually associated with an increase in death rates compared to placebo.

The story of HDL cholesterol is complex. It is apparent that there is more to HDL cholesterol than just the amount or lab value. It’s likely that HDL’s effects also depend on how well the HDL is functioning, although there is not an easy way to measure HDL function in clinical practice.

In Jane’s case, she was right to be concerned. Ultrasound of her carotid arteries showed advanced artery disease despite her healthy lifestyle choices and “good” cholesterol numbers.

What to Do If You Have a Very High HDL

If you have a very high HDL (> 100 mg/dL), it’s important to know that it does not provide blanket immunity from heart disease. And in some, it may be a marker of increased heart disease risk.

Talk to your doctor to better understand your risk for future heart disease and how to optimize your prevention strategy. Some physicians may recommend additional testing to further evaluate heart disease risk such as a CT calcium score or carotid ultrasound.

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About the Author
R. Todd Hurst, MD, FACC

R. Todd Hurst, MD, FACC, FASE, is a board-certified cardiologist, director of the Center for Cardiovascular Health at Banner – University Medicine Heart Institute, and associate professor of medicine at the University of Arizona. He has written more than 50 publications in peer-reviewed journals and regularly speaks nationally and internationally at medical meetings, primarily on the prevention of heart disease.

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