Why is LDL cholesterol the primary target in ASCVD prevention?

LDL particles deposit cholesterol in the arterial intima, where oxidation drives foam cell formation and atherosclerotic plaque growth. Lowering LDL consistently reduces cardiovascular events, which is why high-intensity statins are first-line. Drugs that mainly raise HDL have not reliably reduced events, so LDL lowering remains the main lever.

What findings should prompt suspicion of familial hypercholesterolemia?

Very high LDL from early life, a strong family history of premature coronary disease, and physical findings such as tendon xanthomas on the Achilles or extensor tendons, xanthelasma, and corneal arcus in a young patient. Heterozygous FH reflects a defective LDL receptor and, untreated, leads to early atherosclerotic disease.

What is the danger of combining a fibrate with a statin?

Gemfibrozil impairs the metabolism and transport of statins, raising statin levels and the risk of myopathy and rhabdomyolysis. When a fibrate is truly needed alongside a statin, fenofibrate is preferred over gemfibrozil. Severe hypertriglyceridemia is itself treated with a fibrate mainly to prevent acute pancreatitis.

Clinical Images

Tendon xanthoma · familial hypercholesterolemia clue · tap to expand

Corneal arcus · premature arcus in youth = LDL disease · tap to expand

Atherosclerotic plaque in a coronary artery

Atherosclerotic plaque · LDL oxidation to foam cells · tap to expand

Home Cardiology Dyslipidemia

Dyslipidemia and Lipid Management

LDL is the villain. Triglycerides are the side quest. Statins are the main weapon, but only after you know the goal and the traps.

A 19-year-old man is referred for lipid screening before college sports clearance. He is asymptomatic. His father had a myocardial infarction at age 42 and his paternal uncle died suddenly at 38. On exam you palpate firm, painless nodules over both Achilles tendons. Fasting labs: total cholesterol 410 mg/dL, LDL 340 mg/dL, HDL 38 mg/dL, triglycerides 160 mg/dL, TSH normal.

What is the most likely diagnosis?

Secondary hyperlipidemia from hypothyroidism

Familial hypercholesterolemia

Familial dysbetalipoproteinemia (Type III)

Severe hypertriglyceridemia

The Mechanism Chain

How LDL Builds the Plaque

Tap each lipoprotein card. Front = what it carries. Back = what the board tests.

LDL

Atherogenic core

tap

Board move

LDL cholesterol crosses damaged endothelium, gets oxidized, eaten by macrophages → foam cells → fatty streak → fibrous cap. Lower LDL = lower events. Every time.

HDL

Reverse transport

tap

Board move

HDL picks up cholesterol from peripheral tissues and brings it back to the liver. Low HDL is a risk marker. Drugs that raise HDL have not consistently cut events. LDL lowering still drives therapy.

VLDL

TG rich

tap

Board move

Liver exports triglycerides as VLDL. Lipoprotein lipase strips TG → VLDL becomes IDL → LDL. High TG often means high VLDL and more LDL particles.

IDL

Remnant

tap

Type III trap

IDL remnants accumulate in familial dysbetalipoproteinemia when ApoE cannot clear chylomicron and VLDL remnants. Palmar xanthomas + high TG + high cholesterol = think Type III.

Cause → Effect: the atherosclerosis chain

Endothelial injury: smoking, hypertension, diabetes, or sheer stress lets lipoproteins into the intima.
LDL retention and oxidation: oxidized LDL is antigenic. Macrophages swallow it and become foam cells.
Inflammatory amplification: smooth muscle migrates, fibrous cap forms. Unstable plaque rupture → thrombosis → MI or stroke.
The clinical clue: most patients feel fine until the first event. Physical signs (xanthomas, arcus in the young) are gifts on the exam.

💡 Punch line: Atherosclerosis is an LDL driven disease. Triglycerides matter for pancreatitis risk and as a marker of remnant particles, but LDL lowering is the primary ASCVD prevention lever.

Find the Clues

Presentation and Diagnosis

Most dyslipidemia is silent. The exam gives you tendons, palms, eyes, and family trees.

When the body whispers before the MI

Tendon xanthomas: firm nodules on Achilles tendons or extensor tendons of hands. Classic for familial hypercholesterolemia (FH).
Eruptive xanthomas: yellow papules on buttocks and extensors. Think severe hypertriglyceridemia (often TG > 1000 mg/dL).
Palmar xanthomas: yellow crease deposits. Strong clue for Type III dysbetalipoproteinemia.
Corneal arcus: lipid ring at corneal margin. Arcus before age 45 suggests genetic LDL disease.
Premature ASCVD: MI or stroke in patient or first degree relative men < 55, women < 65.

Fasting lipid panel

Total cholesterol, LDL (direct or calculated), HDL, triglycerides. Diagnose dyslipidemia from the pattern.

Friedewald LDL = TC minus HDL minus TG/5. Invalid if TG > 400 mg/dL. Then order direct LDL.

Rule out secondary causes

Check TSH (hypothyroid), fasting glucose/HbA1c (diabetes), urine protein (nephrotic syndrome), LFTs (cholestasis), medication list.

Fix the driver first. Hypothyroidism can push LDL up 50% and resolves with levothyroxine.

ASCVD risk stratification

Use 10 year ASCVD risk calculator for primary prevention in adults 40 to 75 without diabetes and without known ASCVD.

Risk ≥ 7.5% (clinical medicine) or ≥ 10% (some guidelines) tips you toward statin therapy plus lifestyle.

Genetic and advanced testing when clues fire

LDL ≥ 190 mg/dL, tendon xanthomas, or premature family ASCVD → suspect FH. ApoB and lipoprotein(a) add risk data. Type III: broad beta band on lipoprotein electrophoresis, ApoE genotyping.

FH is autosomal dominant LDL receptor (or ApoB or PCSK9) defects. Treat like high lifetime risk even if the patient is young.

⚠

FH vs "just high cholesterol"

LDL ≥ 190 mg/dL in an adult (or ≥ 160 in a child) plus family history or physical stigmata = familial hypercholesterolemia until proven otherwise. Do not dismiss a 22 year old with LDL 250 as "diet problem only." Start high intensity statin and screen relatives.

Treatment

LDL Goals and Drug Classes

Lifestyle always. Then match intensity to risk. Tap the escalation steps in order.

LDL targets (board anchors)

Very high risk ASCVD (recent MI, multiple events, polyvascular disease): LDL goal < 70 mg/dL, consider < 55 on max therapy.
High risk (established ASCVD, diabetes 40 to 75, LDL ≥ 190, 10 year risk ≥ 20%): LDL < 70 mg/dL.
Moderate risk primary prevention: shared decision; many clinical medicine use LDL < 100 mg/dL once statin started.
Hypertriglyceridemia: TG ≥ 500 mg/dL → fibrate or omega 3 first to prevent pancreatitis. TG ≥ 1000 mg/dL = high pancreatitis risk.

Statin Escalation Ladder

Patient with established ASCVD still has LDL 98 mg/dL on moderate intensity statin. Tap the next three evidence based steps in order.

STEP 1

empty

STEP 2

empty

STEP 3

empty

Drug class cheat sheet

Statins: HMG CoA reductase inhibitors → less hepatic cholesterol synthesis → upregulate LDL receptors. First line. High intensity: atorvastatin 40 to 80, rosuvastatin 20 to 40. Watch for myopathy (check CK if symptomatic).
Ezetimibe: blocks NPC1L1 at the gut brush border → less dietary cholesterol absorption. Add on when statin alone misses goal.
PCSK9 inhibitors: monoclonal antibodies (alirocumab, evolocumab) → more LDL receptors on hepatocytes. For FH or ASCVD not at goal on statin plus ezetimibe.
Bile acid sequestrants: cholestyramine, colesevelam. Bind bile acids → hepatic cholesterol drain. GI side effects. Safe in pregnancy. Separate from other meds by hours.
Fibrates: PPAR alpha agonists → best for high TG. Gemfibrozil plus statin = rhabdomyolysis trap. Fenofibrate plus statin is safer but still monitor.
Omega 3 fatty acids (icosapent ethyl): TG lowering with ASCVD benefit in selected high risk patients on statins.

⚠

Three board traps that kill points

Trap 1: Gemfibrozil plus simvastatin → shared CYP metabolism → rhabdomyolysis.
Trap 2: Statins are contraindicated in pregnancy. Use bile acid sequestrants or lifestyle.
Trap 3: Treat hypothyroidism before blaming the patient for "nonadherence" when LDL stays high.

Prove It

Board Walkthrough

Six vignette bank, 5 dealt per round, answer choices shuffled, never repeat within a round. Tap a wrong answer first to see why it almost works.

Medically reviewed by Fatima Ali, DO and Kaitlyn Cocuzzo, MD · Last reviewed June 2026

Bone Wizardry is an independent educational resource for visual learning in the medical sciences. It is not affiliated with, endorsed by, or sponsored by any licensing or examination board, contains no real or recalled examination questions, and does not guarantee any educational or examination outcome.