Residual Cardiovascular Risk Despite Aggressive LDL Lowering and Optimal LDL-C Reduction (ACC Middle East – October 4, 2025) , Dubai, UAE. (Referencing insights from European Heart Journal, Circulation, and ESC/EAS 2025 Guidelines.)
Residual Cardiovascular Risk Despite Aggressive LDL Lowering and Optimal LDL-C Reduction
(ACC Middle East – October 4, 2025) , Dubai, UAE.
(Referencing insights from European Heart Journal, Circulation, and ESC/EAS 2025 Guidelines.)
Keynotes:
1. LDL cholesterol (LDL-C) – the foundation of prevention
* LDL-C remains the primary causal factor in atherosclerosis, supported by strong genetic, clinical, and interventional evidence.
* Every 1 mmol/L (≈38 mg/dL) reduction in LDL-C lowers major cardiovascular events by about 22–25%.
* It is easy to measure, standardized worldwide, and remains the first-line therapeutic target in all major guidelines (ESC/EAS & ACC/AHA 2025).
* Even with optimal LDL control, many patients experience events — known as residual cardiovascular risk.
2. Understanding how cholesterol and triglycerides circulate — the lipid journey
* After a meal, dietary fat and cholesterol are absorbed by the intestine and packaged into chylomicrons, which deliver triglycerides to muscles for energy and to fat tissue for storage.
* The enzyme lipoprotein lipase (LPL), located on small blood vessels in muscle and fat, breaks down triglycerides, releasing fatty acids for energy or storage.
* As triglycerides are removed, chylomicrons become cholesterol-rich remnants, which can enter artery walls and promote plaque formation.
* Only about 10–20% of dietary cholesterol is absorbed into the bloodstream; the rest is excreted, while 80–90% of blood cholesterol comes from liver production.
* The liver plays the central role: it clears chylomicron remnants and produces VLDL (very low-density lipoproteins) to transport internally made triglycerides and cholesterol.
* As VLDL circulates, it loses triglycerides through LPL and becomes IDL, then LDL, which is rich in cholesterol and capable of promoting atherosclerosis.
* VLDL, IDL, and their remnant forms are also atherogenic, contributing to residual risk even when LDL is controlled.
3. Major contributors to residual risk
* Remnant lipids (lipoproteins)(derived from VLDL and IDL):
– Small, dense, cholesterol-rich particles that persist after triglyceride removal.
– Highly atherogenic because they penetrate arterial walls easily.
– Elevated in metabolic syndrome, insulin resistance, and diabetes.
– Triglycerides >150 mg/dL usually reflect excess remnant particles; direct testing isn’t needed since most labs estimate VLDL-C (≈ TG ÷ 5).
* Lipoprotein(a) [Lp(a)]:
– A genetically inherited LDL-like particle promoting atherosclerosis and thrombosis.
– Unaffected by lifestyle and only minimally influenced by statins.
– Levels remain stable throughout life.
– New RNA-based therapies (pelacarsen, lepodisiran) can lower Lp(a) by >80%, but outcome trials are ongoing (phase 3 results expected in 2026).
* Inflammation:
– Persistent vascular inflammation (↑ hs-CRP) predicts recurrent events even with well-controlled LDL.
– Low-dose colchicine and selective anti-inflammatory agents show promise for secondary prevention.
4. Apolipoprotein B (ApoB) – the most accurate reflection of atherogenic burden
* Each atherogenic particle (LDL, VLDL, IDL, remnants, and Lp(a)) carries one ApoB molecule.
* Measuring ApoB reflects the total number of atherogenic particles, not just their cholesterol content.
* More accurate than LDL-C when triglycerides are high or LDL particles are small and dense.
* Guidelines recommend ApoB <65 mg/dL for very-high-risk patients.
* When ApoB testing is unavailable, Non-HDL cholesterol (Total – HDL) serves as a reliable and accessible substitute.
5. LDL Cholesterol – the primary therapeutic target
* LDL-C reduction is the cornerstone of lipid-lowering therapy and cardiovascular prevention.
* Statins lower cholesterol synthesis in the liver and increase the number of LDL receptors, enhancing LDL clearance from blood.
* Ezetimibe complements statins by blocking intestinal cholesterol absorption, adding another 15–20% LDL-C reduction.
* PCSK9 and its inhibitors – how they work:
– PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) is a natural protein produced by the liver.
– Its normal role is to bind LDL receptors on liver cells and promote their degradation after they remove LDL from the blood.
– When PCSK9 levels are high, fewer LDL receptors remain active, and LDL-C increases in the bloodstream.
– PCSK9 inhibitors (evolocumab, alirocumab) are monoclonal antibodies that block the PCSK9 protein.
– By preventing PCSK9 from destroying LDL receptors, these drugs allow receptors to survive longer and be reused many times.
– This process does not create new receptors, but it extends the lifespan of existing ones, leading to greater LDL clearance from blood.
– PCSK9 inhibitors lower LDL-C by 50–60% and modestly reduce Lp(a).
– They are administered by subcutaneous injection every 2–4 weeks.
– Their effect depends on functional LDL receptors, so they are less effective in homozygous familial hypercholesterolemia (HoFH), where receptors are defective or absent.
Summary:
PCSK9 is a natural liver protein that reduces the number of active LDL receptors.
PCSK9 inhibitors block this protein, preserve LDL receptors, and allow them to be reused — producing a powerful and sustained LDL cholesterol reduction.
6.Triglycerides – an important secondary target
* Elevated triglycerides (TG) represent a key component of residual cardiovascular risk, often indicating excess VLDL, IDL, and remnant lipoproteins.
* A TG level >150 mg/dL usually signals metabolic dysfunction and persistent atherogenic activity even when LDL-C is controlled.
* In clinical practice, TG together with Non-HDL-C or ApoB are sufficient to estimate this risk; direct remnant testing is unnecessary.
Management priorities of hypertriglyceridemia:
* Lifestyle therapy first:
– Weight control, regular exercise, limiting sugars and alcohol, and optimizing diabetes management.
* Pharmacologic options (if lifestyle is insufficient):
– Omega-3 fatty acids (EPA-based): lower TG and mild inflammation.
– Fibrates: indicated for very high TG or mixed dyslipidemia.
– Niacin: rarely used today due to limited benefit and side effects.
– ANGPTL3 inhibition – a novel receptor-independent pathway
* ANGPTL3 (Angiopoietin-like protein 3) is a liver-derived protein that inhibits lipoprotein lipase (LPL), slowing the breakdown of triglycerides in circulation.
* Inhibiting ANGPTL3 enhances LPL activity, leading to lower TG, LDL-C, and HDL-C levels.
* Evinacumab, a monoclonal antibody, is an indirect LPL enhancer that blocks ANGPTL3 — effectively lowering LDL-C (~50%) and TG (40–60%), even in homozygous familial hypercholesterolemia (HoFH).
* It works independently of LDL receptors, which means it remains effective even when these receptors are defective or absent.
* This distinguishes it from PCSK9 inhibitors (evolocumab, alirocumab), which rely on LDL receptor recycling to clear LDL from blood.
* PCSK9 inhibitors act by preventing receptor destruction inside liver cells, allowing existing receptors to be reused multiple times — thereby increasing the number of active receptors and enhancing LDL clearance.
* Evinacumab, however, bypasses this mechanism entirely, providing a receptor-independent reduction in both TG and LDL-C.
* It is given intravenously once a month and was FDA-approved in 2021 for treatment of HoFH.
6. Clinical priorities – order of importance
* LDL-C: Primary and most actionable therapeutic target.
* ApoB: Most precise indicator of total atherogenic particle number.
* Non-HDL-C: Practical, easily available alternative when ApoB is not measured.
* Triglycerides: Secondary target for metabolic and remnant-related risk.
* Lp(a): Lifelong genetic marker; should be measured once to assess inherited risk.
7. Key message
The story of cholesterol and triglycerides begins with food, continues in the liver, travels in the blood as lipoproteins, and ends in the lab as the familiar lipid profile.
Comprehensive prevention requires targeting LDL, ApoB, triglycerides, remnants, and Lp(a) together to overcome the full spectrum of residual cardiovascular risk.
https://www.acc.org/Guidelines/Hubs/Blood-Cholesterol?utm_source=chatgpt.com
