A 72-year-old woman with familial hypercholesterolaemia (heterozygous) presents with recurrent transient ischaemic attacks (TIAs) and carotid atherosclerosis on ultrasound. She has been on atorvastatin 80 mg daily for 8 years. Current lipid profile: LDL-C 110 mg/dL, total cholesterol 210 mg/dL, triglycerides 95 mg/dL, HDL-C 48 mg/dL. Her LDL-C target (given very high cardiovascular risk) is <70 mg/dL. Liver and kidney function are normal. Which agent should be added to achieve target LDL-C and reduce atherosclerotic burden?

Explanation

## Clinical Context This patient has heterozygous familial hypercholesterolaemia (FH) with established atherosclerotic cardiovascular disease (recurrent TIAs, carotid atherosclerosis). Despite maximal statin therapy (atorvastatin 80 mg), her LDL-C remains 40 mg/dL above the very-high-risk target of <70 mg/dL. She requires intensification beyond statin monotherapy. ## Why Ezetimibe + PCSK9 Inhibitor Is Correct **Key Point:** In patients with FH and established ASCVD not at LDL-C goal on high-intensity statin, the next step is ezetimibe + PCSK9 inhibitor (evolocumab, alirocumab, or inclisiran), per ACC/AHA and ESC guidelines. ### Mechanism of Action **Ezetimibe:** - Inhibits Niemann-Pick C1-like 1 (NPC1L1) protein in intestinal brush border - Reduces cholesterol absorption by ~50% - Lowers LDL-C by 15–20% when added to statin - Synergistic with statins (different mechanism) **PCSK9 Inhibitors (Evolocumab):** - Monoclonal antibody against PCSK9 (proprotein convertase subtilisin/kexin type 9) - PCSK9 normally degrades LDL receptors on hepatocytes - Inhibiting PCSK9 → increased hepatic LDLR expression → enhanced LDL clearance - Reduces LDL-C by 50–60% when added to statin ± ezetimibe - Approved for FH and very-high-risk ASCVD **High-Yield:** The combination statin + ezetimibe + PCSK9i can reduce LDL-C by ~70% from baseline and is the standard of care for FH with ASCVD. ### Expected Outcome Statin 80 mg → LDL-C ~110 mg/dL (baseline) + Ezetimibe 10 mg → LDL-C ~90 mg/dL (additional ↓ 15–20%) + Evolocumab 140 mg Q2W → LDL-C ~40–50 mg/dL (additional ↓ 50–60%) **Clinical Pearl:** PCSK9 inhibitors have been shown in trials (FOURIER, ODYSSEY Outcomes) to reduce recurrent MI, stroke, and cardiovascular death in high-risk patients. For a patient with recurrent TIAs and carotid atherosclerosis, achieving LDL-C <70 mg/dL is critical to stabilize plaque and reduce stroke risk. ## Comparison of Options | Agent | LDL-C Reduction | Indication | Role in FH + ASCVD | |-------|-----------------|-----------|--------------------| | **Ezetimibe + PCSK9i** | 65–75% from baseline | FH, ASCVD, inadequate control on statin | **First-line add-on** | | **Fenofibrate** | Minimal LDL effect | Hypertriglyceridemia | Not indicated; TG normal here | | **Niacin** | 15–25% LDL-C ↓ | Mixed dyslipidemia | Outdated; limited evidence for ASCVD benefit | | **Cholestyramine** | 15–30% LDL-C ↓ | Bile acid sequestrant | Rarely used; GI side effects, drug interactions | **Mnemonic — PCSK9 pathway:** **P**roprotein convertase → **C**lears **S**terol-sensing **K**inase → **9** (type 9) → degrades **L**DL **R**eceptors. Blocking PCSK9 = more LDLR on liver = more LDL clearance. ## Safety & Monitoring - Ezetimibe: well tolerated; rare myositis when combined with statin - PCSK9i (evolocumab): subcutaneous injection Q2W or monthly; generally safe; monitor for injection-site reactions, rare autoimmune phenomena - Both agents are safe in renal/hepatic impairment (no dose adjustment needed) - LDL-C should be rechecked 4–12 weeks after initiation [cite:Harrison 21e Ch 395; ACC/AHA Cholesterol Guidelines 2019]