While high cholesterol (either as a high LDL or "bad" cholesterol; or low HDL or "good" cholesterol) certainly contributes to the risk of atherosclerosis and cardiovascular disease, it is not the only contributor. Each year it seems that I have one or two patients that have "no excuse" for having coronary artery disease but they do anyway.
In the same period of time, however, I will see hundreds of patients that have an obvious cause. When doctors see the cause they feel better. When families and patients know the reasons for the disease (have something to blame), they also seem happier. But life doesn’t always work that way. And when it doesn’t, it is sometimes hard to accept therapies that seem to be for diseases that we don’t think that we have.
Some reasons for major blockages that don’t necessarily involve high cholesterol or imbalanced cholesterol numbers include the following partial list:
- High blood pressure, presumably because the stress on the blood vessels walls makes them more likely to develop atherosclerosis.
- Diabetes mellitus, presumably because there is a metabolic defect that leads to abnormal blood vessels.
- Heredity, presumably because your ancestors donated some unusual genes.
- Smoking, because we know that many elements in tobacco smoke play havoc with the walls of the blood vessels, causing contraction of the blood vessels and damaging their internal structures.
- Radiation, this can damage the blood vessels by burning them, and appears years after exposure. The most common types of radiation that cause this are for cancer of the breast, lung, and "mantle" radiation for certain types of lymphoma
- Chemotherapy, this usually causes damage the heart muscle rather than to the coronary arteries.
- Cocaine use, due to its powerful constricting of blood vessels.
- Toxic fumes.
- Vascular and hemodynamic "stress".
- Inflammatory diseases and connective tissue disease.
- Infections, such as endocarditis.
- Blood clotting disorders.
- Advanced age.
In the future, we will have more information on why certain people do not have some "reason" for their clinical situation through the help of studies in genomics, proteomics and metabalomics, but for now we do not truly understand by what mechanism some people develop coronary artery blockage for no apparent reason other than those listed above. At this point in time we are limited to what we learn from statistics about the relationships between end points and certain diseases and risk factors. We will ultimately develop better tests that give us more information. Fortunately, despite the absence of any clear-cut reason or an early test to predict the initial event in some people, the standard therapies do work as well in these people as in those that have multiple risks. They take a bit more explaining, though. It is reasonably easy to explain to a patient with a cholesterol of 400 mg/dl that we need to lower the number to reduce risk. It is not so obvious that this will help the patient with a cholesterol of 200, but it does. Fortunately also, the angioplasties, stents and coronary bypasses that we use also work in this situation.