In a patient with homozygous familial hypercholesterolemia who fails to achieve LDL‑cholesterol below ~100 mg/dL despite maximally tolerated high‑intensity statin, ezetimibe, and a PCSK9 inhibitor, when should LDL apheresis be started and how should it be performed and monitored?

LDL Apheresis in Homozygous Familial Hypercholesterolemia

Lipoprotein apheresis should be initiated by age 3 years (and no later than age 8) when LDL-cholesterol remains above goal despite maximally tolerated statin, ezetimibe, and PCSK9 inhibitor therapy. 1

When to Start LDL Apheresis

The decision to initiate apheresis is straightforward in homozygous FH:

• Start apheresis when LDL-C goals are not achieved with maximal medical therapy (high-potency statin + ezetimibe + PCSK9 inhibitor if there is residual LDL receptor activity) 1
• Target LDL-C goals that trigger apheresis consideration:
  • <100 mg/dL without ASCVD or major risk factors
  • <70 mg/dL with imaging evidence of ASCVD or additional major risk factors
  • <55 mg/dL with previous ASCVD event 1
• Age considerations: Ideally start at age 3, but absolutely no later than age 8 years 1

Important caveat: Before initiating apheresis, ensure the patient has trialed a PCSK9 inhibitor (evolocumab or alirocumab) and demonstrated at least 15% additional LDL-C reduction if they have any residual LDL receptor activity 1. In patients with biallelic LDLR null mutations, PCSK9 inhibitors will be ineffective and should not delay apheresis initiation 1.

How to Perform LDL Apheresis

Vascular Access

• Initial access: Peripheral veins 1
• If peripheral access fails: Arteriovenous fistula (particularly relevant for children) 1
• Avoid: Central venous catheters except as emergency or temporary measure 1

Treatment Volume and Frequency

• Volume: Treat 1-2 plasma volumes per session 1
  • Plasma volume = body weight (kg) × 0.045 L
  • Blood volume = plasma volume / (1 - hematocrit)
• Frequency: Weekly or fortnightly sessions 1
• Special consideration for small children (<30 kg): Plasma exchange requires smaller extracorporeal blood volume and is recommended as alternative 1

Concurrent Medications

• Continue all lipid-lowering therapy during apheresis (statins, ezetimibe, PCSK9 inhibitors) 1
• Timing of injectable agents: Administer PCSK9 inhibitors soon after (not immediately before) apheresis procedure 1
• Anticoagulation management:
  • Warfarin: Adjust dose or discontinue several days before procedure 1
  • Direct oral anticoagulants (apixaban, dabigatran, rivaroxaban): Stop only on day of apheresis due to shorter half-life 1
  • Antiplatelet therapy: Continue throughout 1
• ACE inhibitors: Do NOT use with apolipoprotein B adsorption-based apheresis; substitute with angiotensin-receptor blockers 1

How to Monitor LDL Apheresis

Acute Efficacy Monitoring

Measure immediate LDL-C reduction at each session:

• Target 65-70% acute reduction in both LDL-C and Lp(a) 1

Interval Mean Calculation (Kroon Formula)

Calculate the time-averaged LDL-C between sessions using:

• Formula: C_mean = C_min + k(C_max - C_min)
  • C_max = pre-procedure value
  • C_min = post-procedure value
  • k = 0.65 for HoFH patients 1
  • k = 0.71 for HeFH patients on statins with fortnightly apheresis 1

Use this interval mean to:

• Compare against LDL-C goals for HoFH
• Adjust treatment volume and/or frequency as needed 1

Cardiovascular Disease Monitoring

Annual monitoring in children and adults with HoFH:

• Echocardiography: For aortic root disease 1
• Coronary angiography: For coronary artery disease (as clinically indicated) 1

Laboratory Monitoring

• Routine full blood counts: Monitor regularly 1
• Iron supplementation: Initiate if iron-deficiency anemia develops with long-term apheresis 1

Adjunctive Therapies to Consider

If apheresis plus conventional therapy (statin + ezetimibe + PCSK9 inhibitor) fails to achieve goals:

Add lomitapide or evinacumab, particularly in patients with progressive ASCVD 1. These agents:

• Increase LDL-C lowering beyond apheresis alone
• May reduce apheresis frequency
• Can sometimes replace apheresis if tolerated 1

Critical point: The evidence shows that multimodal therapy combining apheresis with newer agents (lomitapide, evinacumab) can achieve previously unattainable LDL-C targets, even in LDLR-null patients 2.

Common Pitfalls

1. Delaying apheresis initiation beyond age 8 in children—this significantly increases ASCVD risk 1
2. Using ACE inhibitors with apoB adsorption-based apheresis systems—switch to ARBs 1
3. Stopping antiplatelet therapy during apheresis—this should be continued 1
4. Administering PCSK9 inhibitors immediately before apheresis—give soon after instead 1
5. Not monitoring for iron-deficiency anemia with chronic apheresis 1