Is phlebotomy indicated for elevated hematocrit (blood cell concentration) levels in patients with Eisenmenger syndrome?

Phlebotomy in Eisenmenger Syndrome: Indication Criteria

Phlebotomy with isovolumic replacement should only be performed when patients have moderate to severe hyperviscosity symptoms AND hematocrit exceeds 65%, and must never be done in asymptomatic patients regardless of hematocrit level. 1

When Phlebotomy IS Indicated

Phlebotomy is appropriate only when ALL of the following criteria are met:

• Moderate to severe hyperviscosity symptoms are present including headache, poor concentration, faintness, dizziness, fatigue, tinnitus, blurred vision, paraesthesia of fingers/toes/lips, muscle pain, and weakness that interfere with activities 1, 2
• Hematocrit exceeds 65% 1
• Patient is adequately hydrated (dehydration must be excluded) 1, 2
• Iron stores are adequate (iron deficiency must be excluded) 1, 2

This represents a Class IIa recommendation with Level C evidence from multiple European Society of Cardiology and European Respiratory Society guidelines. 1

Critical Technical Requirements

When phlebotomy is performed, strict adherence to the following protocol is mandatory:

• Remove only one unit of blood (approximately 500 mL over 30-45 minutes) 1, 3
• Always provide isovolumic replacement with equal volume of isotonic saline or dextrose 1
• Limit frequency to no more than 2-3 times per year 1
• Symptoms typically resolve after removal of one unit 1

When Phlebotomy Should NOT Be Performed

Phlebotomy is contraindicated or inappropriate in the following situations:

• Asymptomatic patients, regardless of hematocrit level 1
• Mildly symptomatic patients, regardless of hematocrit level 1
• Presence of dehydration 1, 2
• Iron deficiency (check serum ferritin, MCV) 1, 2
• Hematocrit <65% in iron-replete patients (hyperviscosity symptoms are unlikely) 1

Critical Pitfalls to Avoid

Excessive or inappropriate phlebotomy causes serious complications:

• Iron deficiency from repeated phlebotomy produces iron-deplete red cells and microcytosis that paradoxically increase blood viscosity 1, 2
• Microcytosis is the strongest independent predictor of cerebrovascular events in Eisenmenger patients 1
• Iron deficiency should be treated with iron supplementation 3
• Routine prophylactic phlebotomy based solely on hematocrit level without symptoms is harmful 1

Physiological Rationale

The elevated hematocrit in Eisenmenger syndrome represents an appropriate compensatory response to chronic hypoxemia. 3 The secondary erythrocytosis helps maintain oxygen delivery to tissues in the setting of chronic arterial desaturation. 2 Indiscriminate reduction of hematocrit removes this compensatory mechanism without addressing the underlying problem and may worsen outcomes. 1

Hyperviscosity symptoms occur due to the rheological effects of extremely elevated hematocrit (typically >65%), not from the elevated red cell mass per se. 1 The goal is symptom relief, not normalization of hematocrit. 1

Monitoring Requirements

All Eisenmenger patients require regular laboratory monitoring:

• Complete blood count with MCV 1, 2
• Serum ferritin (and potentially serum iron, transferrin, transferrin saturation for earlier detection of iron deficiency) 1
• Assessment for hyperviscosity symptoms at each visit 1, 2