Cholesterol and Coronary Artery Disease: What the Numbers Actually Mean

Introduction

As a surgeon, the patients I operate on for coronary disease almost never arrive because cholesterol made them feel unwell. Cholesterol does not hurt. It produces no symptom at any level, for years, until the artery it has been narrowing finally fails — as angina, or as a heart attack.

That silence is the whole problem, and it is why understanding a lipid profile matters more than it appears to.

Cholesterol is not the enemy

Cholesterol is essential. Every cell membrane in the body contains it, and it is the raw material for vitamin D, for bile acids that digest fat, and for hormones including cortisol, oestrogen and testosterone. Your liver manufactures it because you need it.

The issue is not its existence but its transport, its quantity, and where it ends up.

Reading a lipid profile

LDL cholesterol — carries cholesterol from the liver out to the tissues. When there is more than the body needs, LDL particles penetrate artery walls. This is the number that matters most.
HDL cholesterol — carries cholesterol back to the liver for disposal. Higher levels are broadly favourable, though raising HDL with drugs has not been shown to reduce events, so it is a marker rather than a target.
Triglycerides — a different fat, strongly linked to diet, alcohol, obesity and insulin resistance. High levels often travel with diabetes and metabolic syndrome.
Non-HDL cholesterol — total minus HDL. It captures all the harmful particles together and is often a better guide than LDL alone, particularly when triglycerides are high.
Lipoprotein(a) — largely genetically determined and not modified by diet. Worth measuring at least once, especially with a strong family history of early heart disease.

What actually happens inside the artery

This is the part rarely explained, and it changes how people think about treatment.

LDL particles cross the inner lining of the artery and lodge in the wall. There they become oxidised, which the immune system reads as a threat. White cells move in to engulf them and become foam cells. The accumulation forms a plaque inside the artery wall — not a deposit sitting loose in the channel like sediment in a pipe, which is the usual mental picture and the wrong one.

The body walls the plaque off with a fibrous cap. And here is the crucial point: the dangerous plaque is often not the biggest one. A large, stable, heavily calcified plaque may narrow the artery and cause predictable angina on exertion. A smaller plaque with a thin inflamed cap can rupture without warning. When it does, the body treats it as an injury and forms a clot — and that clot can block the artery in minutes. That is a heart attack, and it is why people with "only mild narrowing" can still have one.

What your target should be

There is no single correct LDL number for everyone. The target depends on your overall cardiovascular risk, and it falls as risk rises:

Someone young with no risk factors has a relatively relaxed target.
Someone with diabetes, hypertension, smoking, chronic kidney disease, or a strong family history has a lower one.
Someone who has already had a heart attack, a stent, or bypass surgery has the lowest target of all — because the disease has already proven what it can do.

After bypass surgery, aggressive lipid lowering is not optional housekeeping. Grafts fail over time when the underlying disease process continues, so the medication is protecting the operation.

What genuinely lowers risk

Diet

Replace saturated and trans fats rather than simply removing fat. Trans fats — produced in repeated deep frying and some processed foods — are the worst offenders, raising LDL while lowering HDL. Increase soluble fibre from oats, legumes, vegetables and fruit. Include oily fish. Dietary cholesterol itself, in eggs for example, has far less effect on blood cholesterol than saturated fat does, which is why egg advice has moderated.

Activity and weight

Regular aerobic activity lowers triglycerides, raises HDL and improves insulin sensitivity. Losing excess weight, particularly abdominal fat, improves the whole profile.

Smoking

Smoking lowers HDL, damages the artery lining directly and makes plaque rupture more likely. Stopping is the single most valuable change most smokers can make.

Medication

Lifestyle alone often cannot reach target, because a large share of circulating cholesterol is manufactured by the liver rather than eaten. Statins reduce that production and also stabilise plaque, making rupture less likely — a benefit beyond the number itself. Ezetimibe and newer agents are added when statins alone are insufficient or not tolerated.

Two mistakes are common and costly: stopping a statin because the number has normalised — the number normalised because of the statin — and stopping because of aches without first discussing them, when dose or drug can usually be adjusted.

Who should be tested, and when

Adults should have a lipid profile as part of general health assessment, earlier and more often with diabetes, hypertension, obesity, smoking, or a family history of premature heart disease. A very high level in a young person, or a family history of heart attacks before 55 in men and 65 in women, raises the possibility of familial hypercholesterolaemia — an inherited condition that requires treatment from a young age and screening of relatives.

Key points

Cholesterol is necessary; excess LDL is the problem.
Plaque forms inside the artery wall, and the rupture-prone plaque is not always the largest.
Your LDL target depends on your total risk, and is lowest after a cardiac event or surgery.
Diet, activity and stopping smoking matter — but much of your cholesterol is made, not eaten.
It is silent. The only way to know your numbers is to measure them.

This article is general health education and is not personal medical advice. Do not start, stop or change any medication without consulting your doctor. If you have chest pain now, seek emergency assessment.