Lipid Disorders

Lipid disorders, also known as dyslipidemias, involve abnormal levels of lipids in the blood. They are significant risk factors for cardiovascular disease. Here’s an overview of the classification, diagnosis, and management of lipid disorders:

Classification

Lipid disorders can be classified based on which component of the lipid profile is abnormal:

  • Hypercholesterolemia: Elevated total cholesterol.
  • Hypertriglyceridemia: Elevated triglycerides.
  • Combined hyperlipidemia: Elevated cholesterol and triglycerides.
  • Low HDL cholesterol: Decreased high-density lipoprotein (HDL) cholesterol.

Sub-classification

Lipid disorders can also be:

  • Primary: Genetic or inherent.
  • Secondary: Resulting from other medical conditions (like hypothyroidism, diabetes, or nephrotic syndrome) or lifestyle factors.

Diagnosis

The diagnosis is primarily based on fasting blood tests to measure:

  • Total cholesterol
  • LDL cholesterol (often calculated using the Friedewald equation)
  • HDL cholesterol
  • Triglycerides

Management

The goal of managing lipid disorders is to reduce the risk of atherosclerotic cardiovascular disease (ASCVD). Management strategies include:

Lifestyle Modifications

  1. Dietary Changes:
    1. Reduce Saturated and Trans Fats: Limiting foods high in saturated fats (like red meat and full-fat dairy products) and trans fats (found in many fried and processed foods).
    2. Increase Soluble Fiber: Foods rich in soluble fibre (such as oats, beans, lentils, apples, and pears) can help reduce LDL cholesterol.
    3. Incorporate Healthy Fats: Include more monounsaturated and polyunsaturated fats (found in olive oil, avocados, nuts, and fatty fish) in your diet.
    4. Substitute: Plant sterol-enriched milk, margarine or cheese products.
  2. Regular Physical Activity:
    • Engage in at least 150 minutes (5 x 30) of moderate aerobic exercise or 75 minutes (5 x 15) of vigorous aerobic activity per week
    • Muscle-strengthening activities on 2 or more days per week.
  3. Weight Management:
    • Losing weight if overweight can help lower LDL cholesterol and increase HDL cholesterol.
  4. Quit Smoking:
    • Smoking cessation improves the HDL cholesterol level and overall heart health.
  5. Limit Alcohol Consumption:
    • Moderate use of alcohol has been linked with higher levels of HDL cholesterol, but the benefits aren’t strong enough to recommend alcohol for anyone who doesn’t already drink.

Pharmacotherapy

  1. Statins:
    • The first line for lowering LDL cholesterol (e.g., atorvastatin, simvastatin, rosuvastatin).
    • Inhibit HMG-CoA Reductase
    • Statins reduce cardiovascular events and are first-line for most patients at risk.
  2. Ezetimibe:
    • The second line for lowering LDL
    • Inhibits cholesterol absorption in the intestines and can reduce LDL cholesterol levels.
    • Works synergistically with statins
  3. Fibrates:
    • Gemfibrozil and fenofibrate
    • Reduce triglycerides and can increase HDL cholesterol.
  4. Omega-3 Fatty Acid Supplements (Fish Oil):
    • It can help reduce triglycerides.
  5. Bile Acid Sequestrants:
    • Cholestyramine, colestipol, colesevelam
    • Lower LDL cholesterol by binding bile acids in the intestine.
  6. PCSK9 Inhibitors:
    • Evolocumab, alirocumab)
    • Monoclonal antibodies that can dramatically reduce LDL cholesterol.
    • They’re reserved for patients with very high cholesterol levels or those who don’t respond to or tolerate statins.
  7. Niacin (Vitamin B3):
    • Reduces LDL cholesterol and triglycerides and raises HDL cholesterol.
    • Due to side effects (flushing) and the availability of other agents, its use has declined.

Monitoring and Follow-Up

  • Response to therapy targets:
    • Cholesterol <4.0 mmol/L
    • Triglyceride <2.0 mmol/L
    • HDL – Cholesterol >=1.0 mmol/L
    • Non-HDL – Chol. <2.5 mmol/L
    • LDL – Cholesterol <2.0 mmol/L
  • Suggested frequency of lipids measurement (Red Book):
    • High risk – every 12 months
    • Medium risk – every 2 years
    • Low risk (> 45 years) – every 5 years
    • Low risk (Aboriginal and Torres Strait Islanders >35 years) – every 5 years
  • Monitoring for medication side effects (e.g., liver function tests for statin users).

Additional Considerations

Individualized risk assessment is critical. Some patients might have lipid levels within the “normal” range but may still benefit from lipid-lowering therapies based on other risk factors.

Decision-making should consider the overall risk of ASCVD, which will involve tools like the CVD risk calculator.

https://www.cvdcheck.org.au/calculator