From the Guidelines
Yes, secondary erythrocytosis is associated with an increased risk of thrombosis. This condition, which occurs when the body increases red blood cell production in response to hypoxia or certain medical conditions, can lead to hyperviscosity of the blood, impairing normal flow, particularly in small vessels, and creating conditions favorable for clot formation. The risk of thrombosis is especially pronounced when hematocrit levels exceed certain thresholds, and patients with secondary erythrocytosis may require therapeutic phlebotomy to maintain hematocrit below these thresholds, particularly if they have additional risk factors for thrombosis such as hypertension, diabetes, or smoking. The underlying mechanism involves not only increased blood viscosity but also enhanced platelet activation and aggregation in the setting of elevated red cell mass, as noted in studies such as 1 which discuss the management of adults with congenital heart disease and the implications of cyanosis and secondary erythrocytosis on thrombotic risk. Unlike polycythemia vera (a primary erythrocytosis), secondary forms don't typically require cytoreductive therapy, but management of the underlying cause (such as chronic hypoxemia, sleep apnea, or certain tumors) is essential to reduce thrombotic risk, as highlighted in guidelines like those found in 1, which discuss the prevention of cancer-associated thrombosis and the specific considerations for patients with myeloproliferative neoplasms. Key considerations include:
- The definition and implications of secondary erythrocytosis, as discussed in 1
- The role of therapeutic phlebotomy in managing hyperviscosity symptoms, as outlined in 1 and 1
- The importance of managing underlying causes of secondary erythrocytosis to reduce thrombotic risk, as emphasized in 1 and 1
- The distinction between secondary erythrocytosis and primary erythrocytosis (like polycythemia vera), and the different management approaches for these conditions, as noted in 1.
From the Research
Association Between Secondary Erythrocytosis and Thrombosis Risk
- Secondary erythrocytosis is associated with an increased risk of thrombosis, although the evidence is not as strong as it is for primary erythrocytosis, such as polycythemia vera (PV) 2, 3.
- In patients with cyanotic congenital heart disease (CCHD) and secondary erythrocytosis, an association between elevated hematocrit and thrombosis has not been established, but phlebotomy is often performed to reduce hematocrit levels 2.
- The treatment of secondary erythrocytosis should be directed at the underlying cause, and a pragmatic approach is recommended to identify the cause of this condition 3.
Mechanisms and Risk Factors
- Severe erythrocytosis is associated with increased whole blood viscosity and impaired blood flow, which can lead to tissue hypoxia and increased synthesis of erythropoietin 4.
- However, the location of an oxygen sensor in the kidneys controlling erythropoietin production prevents the development of a vicious circle, with erythrocytosis causing more erythrocytosis 4.
- Risk factors for thrombosis in patients with myeloproliferative neoplasms, such as PV and essential thrombocythemia (ET), include advanced age, leukocytosis, and thrombosis history 5.
Management and Treatment
- The main goal of therapy in patients with secondary erythrocytosis is to prevent thrombohemorrhagic complications, and treatment should be directed at the underlying cause 3.
- In patients with PV, low-dose aspirin and phlebotomy (hematocrit target <45%) are recommended for low-risk patients, while high-risk patients may require additional treatment with hydroxyurea or other agents 5.
- The combination of aspirin and anticoagulants is associated with an increased risk of hemorrhage in patients with PV, and the risk of hemorrhage should be carefully considered when managing these patients 6.