Why Do I Have Lipidemia?
Lipidemia is the medical term for the presence of lipids in the blood and clinically, when referring to elevations in lipids, this term is used synonymously with the more accurate term, dyslipidemia. It can be either (or both):
“Mixed hyperlipidemia” is both hypercholesterolemia and hypertriglyceridemia.
Cholesterol is a fatty substance used in the body for many purposes, such as synthesis of hormones, vitamin D, and digestive chemicals. It also provides the coating around nerves that insulates them to conduct signals faster, the absence of which would be incompatible with life. There is also a detrimental effect of cholesterol when certain subtypes of it are either too high or too low.
There are different types of cholesterol and their abnormal levels have clinical relevance to the risk of cardiovascular disease.
- LDL-C: Low-density lipoprotein cholesterol, elevations of which raise the risk of cardiovascular disease, since this is the cholesterol whose accumulation builds plaques in arteries, leading to obstruction and embolic events such as stroke and ischemia of the heart and other organs.
- HDL-C: High-density lipoprotein cholesterol, elevations of which actually lower the risk of cardiovascular disease because it carries cholesterol from the rest of the body to the liver for elimination. Alternately, lower-than-normal HDL-C impairs this protective mechanism.
- VLDL-C: Very low-density lipoprotein cholesterol, which like the LDL-C-accumulating cholesterol, does the same in accumulating triglycerides when higher than normal.
Hypercholesterolemia can be a genetic disease, “familial hypercholesterolemia,” in which there is reduced clearance of low-density lipoprotein cholesterol (LDL-C).
Hypertriglyceridemia refers to abnormal elevations of triglycerides in the blood. These are a type of non-cholesterol fat from food; calories not burned are stored in body fat as triglycerides. Triglycerides are elevated with overeating, smoking, excessive alcohol, liver or kidney disease, and type 2 DM.
Along with elevations in LDL-C or too-low levels of HDL-C, hypertriglyceridemia is associated with higher risk of cardiovascular disease and stroke.
Lipid profiles are done to identify those with dyslipidemia–either hypercholesterolemia, hypertriglyceridemia, or both. These is done to determine the the risk of developing cardiovascular disease, including coronary artery disease and neurological stroke.
Statins are lipid-lowering medications used to re-balance cholesterol and triglycerides into normal ranges as part of a heart-healthy strategy. They work by interfering with the synthesis of cholesterol. Even the VLDL is reduced, which lowers the triglyceride accumulation that the VLDL normally carries.
Diagnosis of Lipidemia
There are different types of cholesterol and their abnormal levels have clinical relevance to the risk of cardiovascular disease. All patients >20 years of age should have an assessment for risk of cardiovascular disease (CVD), since the earliest stages of dyslipidemia begin in childhood. When lipid levels are abnormal enough to identify those who statistically have an elevated risk of having a CVD event in the next 10 years, it should prompt treatment with lipid-lowering medicines.
Those at higher risk for CVD should also be evaluated using the lipid profiles:
- Strong family history of dyslipidemia, atherosclerosis, heart disease, stroke, or arterial disease.
- Obese patients.
Statins are the most powerful drugs for reconciling lipid abnormalities to normal levels. Periodic lipid tests are done that assess total cholesterol, LDL-C, HDL-C, non-HDL cholesterol (total cholesterol minus HDL-C), and triglycerides after a diagnosis of hyperlipidemia is made and statins are begun.
A lipid panel that measures LDL-C, HDL-C, and triglycerides is used to establish the diagnosis as well as identify the severity of disease, based on the values obtained for
- Total cholesterol (normal < 200 mg/dL)
- LDL cholesterol levels > 130 mg/dL raise the risk for heart attacks, strokes, and other cardiovascular complications
- HDL cholesterol (HDL-C) levels > 60 mg/dL lower the risk of cardiovascular complications; alternately, HDL-C levels < 60 mg/dL raise the risk of cardiovascular complications
- Non-HDL cholesterol (total cholesterol minus HDL-C; normal is <160 mg/dL)
- Normal levels are <150 mg/dL
- > 150 to 499 mg/dL (mild)
- 500-886 mg/dL (moderate)
- >886 mg/dL (severe)
A diagnosis of elevations in LDL-C and triglycerides, and/or a lower-than-normal level of HDL-C, creates high risk for cardiovascular events and such patients are evaluated/treated for other risk factors such as hypertension, hyperglycemia, peripheral artery disease, and other conditions, since these are associated co-morbidities frequently related to abnormal lipid levels. (The diabetic patient at higher risk due to dyslipidemia is evaluated like any high-risk cardiovascular patient, with EKGs, echocardiogram, and stress testing.)
Decision to Treat
When elevated lipids are discovered by lipid panel blood tests, evidence clearly shows that lowering them reduces the risk of cardiovascular disease (CVD) and CVD-related events:
- Coronary artery disease: Including myocardial infarction (MI), angina, or heart failure
- Cerebrovascular disease: Presenting as stroke or TIA
- Peripheral artery disease: Suspected with claudication (pain of muscles with exertion) or limb ischemia
- Aortic atherosclerosis: Such as thoracic or abdominal aortic aneurysm
Treatment for abnormal lipid levels is based on the computed risk of suffering a CVD event within 10 years, predicted by a what is called a CVD Risk Calculator. There are many versions of CVD calculators, but they generally all use lipid levels along with other comorbidities, such as diabetes, hypertension, smoking, family history, kidney disease, and obesity.
Treatment with Statins
Statins, taken daily, usually in the evening, are the most powerful drugs for lowering LDL-C. Different statins may also impact the other cholesterol and triglyceride values favorably, although the target is LDL-C.
One of the moderate-intensity statins is used initially:
- Lovastatin (Mevacor, Altoprev), 40 mg
- Pravastatin (Pravachol), 40 mg
- Simvastatin (Zocor), 40 mg
- Atorvastatin (Lipitor), 10 to 20 mg
- Rosuvastatin (Crestor), 5 to 10 mg
When those fail, higher-intensity statins are considered:
- Atorvastatin (Lipitor), 40 to 80 mg
- Rosuvastatin (Crestor), 20 to 40 mg
Current guidelines recommend that any adults aged 40-75 without CVD but with an LDL-C between 70-189 mg/dL should be treated:
- Treatment with moderate-intensity statin therapy is recommend for those with an estimated 10-year CVD risk between 5.0-7.5%
- Those with an estimated 10-year CVD risk ≥7.5% are treated with moderate-to-high intensity statin therapy
For patients at high risk, the LDL-C should be lowered to <100 mg/dL, or at least 50% of the original baseline level. For very high-risk patients, LDL-C should be lowered to <70 mg/dL, or a reduction of at least 50% of the original baseline levels.
Any prescribed statin protocol requires periodic re-assessments, measuring LDL-C response to the prescribed statins at the 6-week mark, followed by lipid panels yearly. During these times interval checks on blood pressure, signs and symptoms of atherosclerotic disease, glucose and hemoglobin A1c levels, weight, and liver/kidney function can be made.
Prevention of Lipidemia
An elevated LDL-C, a low HDL-C, and/or high triglycerides each require treatment with statins to prevent the lipid-related risks of cardiovascular disease. Along with statins, other risks, individually, should be addressed to reduce the global risk of heart disease.
- Education: Important so that the patient can partner with the treating physician to identify a treatment goal and the health benefits that come with reaching it.
- Nutritional counseling: Provides a strategic yet reasonable plan for caloric reduction and a shift in diet to favorably impact lipid levels, obesity and the metabolic syndrome, hypertension, and poor glycemic control.
- Smoking cessation: Counseling and possibly medication (smoking cessation aid) to assist in smoking cessation.
- Exercise: interacting with diet, they are both mutually important and interrelated. Physical exercise is also important in cognition, which improves motivation for the other risk reduction factors.
- Blood pressure control: Medications (antihypertensives) are used if diet and exercise do not reduce an elevated blood pressure.
- Good glycemic control: Diabetics already understand hyperglycemia and its toxic effects on the heart and cardiovascular system, but those with “prediabetes” should be counseled how diabetic risk overshadows all of the other risks.
Prevention of Statin-Induced Myopathy
Statins affect the synthesis of coenzyme Q10 (ubiquinone), which is an important part of muscle cell energy production. Because of this, rare cases of muscle injury can occur:
- Myalgia: Muscle pain and soreness
- Myopathy: Muscle weakness
- Myositis: Muscle inflammation
- Myonecrosis: Elevations of enzyme markers (CK) of muscle injury
- Rhabdomyolysis: When myoglobin from myonecrosis is excreted into the urine with or without renal failure
Myopathy can be prevented by judicious choice of which statin is prescribed, based on patient medical history, academic studies, other drugs being used by the patient, and dose adjustments. Other strategies include alternate-day dosing or merely switching statins.
Prevention of the dyslipidemia that calls for lipid-lowering medicines can be challenging, since it often is a genetic disease, but education, counseling, increased activity and weight management will cluster into a highly beneficial risk reduction/prevention program.