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Cholesterol Management 101

with Michael Richman, MD, FACS

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Thursday, June 26, 2008

Advanced Cholesterol Testing

I was originally planning on starting to talk about medicines used to lower Triglycerides but due to the untimely death of Tim Russert, I wanted to discuss Advanced Cholesterol Testing. Last week I had the great pleasure of being interviewed on a nationally syndicated radio show. I was asked what I believed could be done to bring more awareness to physicians and the public about the epidemic of Cardiovascular morbidity and mortality? The entire podcast is available on my website and the feedback that I have received from my patients was that I took a difficult topic and made it so easy to understand for the average person. I hope that after listening and reading this posting you will see the need to perform this special type of cholesterol testing.

Over three years ago, I opened The Center for Cholesterol Management as the only free standing lipid clinic in the Los Angeles area dedicated to Advanced Lipoprotein Particle Testing. As a board certified Cardiothoracic surgeon, I feel I have a unique perspective about coronary artery disease in that I am able to clinically correlate angiographic findings with actual operative findings which in so many incidences are discordant. Coronary artery disease is a largely misunderstood entity.

Hyperlipidemia is the most modifiable risk factor leading to Atherosclerosis, yet traditional lipid testing may miss up to 50% of people who have abnormal lipids. Prevention includes identifying people at risk and providing the best treatment individualized to their specific problem.

It is with this background that I will discuss Advanced Lipid Testing and its role in identifying all patients at lipid related risk and as a tool for management of abnormal lipid levels. I often ask myself how come health care providers do not understand this type of testing? I honestly believe that if all people are identified as being at risk, and then if treated appropriately, we would significantly change the face of Cardiovascular morbidity and mortality.

As physicians, we are taught in medical school that it is all about Total Cholesterol, HDL-C, LDL-C, and Triglycerides, yet few really understand the limitations of traditional lipid testing. I hear everyday physicians say that if it is so important why isn’t everyone doing it? I believe the answer is that one does not want to change from old patterns of thinking, and according to other physicians, it is too much trouble to learn and understand. Recently, the ADA/ACC released a Joint Concession Statement on Lipoprotein Management in patients with Cardiometabolic Risk(CMR). The full text is available on my website. I believe it is mandatory reading and states that patients with CMR in the moderately high, high, and very high risk groups, it is now the standard of of care to quantify lipoproteins by performing ApoB or LDL-P on all patients to ascertain risk and as a goal of therapy.

As we all know that since sterols are insoluble in the blood, they need to be driven around the body in Lipoproteins. These include HDL-P, VLDL-P, and LDL-P among others. HDL particles are also known as ApoA and all the particles that cause atherosclerosis are known as ApoB. Although NCEP( National Cholesterol Education Panel) recommends calculating the non-HDL cholesterol, this value only can alert the physician that there may too many lipoprotein particles despite having a normal LDL-C. Approximately 90-95% pf the circulating ApoB particles are LDL-P which have a half-life of around 3 days. As varying amounts of Triglycerides and Cholesterol are driven around the body, in what I tell my patients are “cars”, the ApoB particles enter the arterial wall if there are too many of the “cars” circulating in the bloodstream.

By simple diffusion, all the bad particles flow from inside the artery and move into its wall and are “eaten” by macrophages which become foam cells and are the hallmark of Atherosclerosis. In eight published studies of over 11,000 subjects using LDL-P and other Lipoprotein concentrations remained the most significant and independent predictor of cardiovascular morbidity and mortality over any other lipid parameter including the usual ratio that all physicians and patients talk about. . In a nutshell, it is the number of LDL particles that matter most… it is the number of cars that cause a traffic jam, not the people in the cars. For example, what if a person with moderate risk has met NCEP guidelines and has a LDL-C of 110mg/dl.

How do I know that there are not 100 cars with one person driving or two big buses with 55 people? The answer is that I do not unless I measure LDL-P directly by using NMR or as a second option measuring ApoB with Gel Electrophoresis. Traditional testing measures the passengers and lipoprotein testing measures the cars, and it is the number of cars(LDL-P) measured by NMR (Nuclear Magnetic Resonance) that are the most numerous ApoB particles in the body and matter most in the development of Atherosclerosis.

Although a comprehensive review of each of the methodologies to perform Lipoprotein Testing is beyond the scope of this post, I feel that measuring LDL particles directly using NMR is the best way to ascertain someone’s true risk and then use that number as a guide to management. As I said in my posting about Alex Trebek, the CDC states that 50% of people who have heart attacks have “normal” cholesterol. I hope you now understand why this can happens, having a normal LDL-C but high LDL-P, and be proactive and ask that your physician performs Advanced Cholesterol Testing.

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Posted by: Michael Richman, MD, FACS at 2:39 pm

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