From the Guidelines
Polycythemia is a significant risk factor for thromboembolic events in patients with Chronic Heart (CH) disease, particularly when hematocrit levels exceed 51%. When a patient has polycythemia, their blood contains an abnormally high concentration of red blood cells, which increases blood viscosity and impairs normal blood flow, thereby disrupting the body's autoregulatory mechanisms and increasing the risk of thrombotic events in various vessels, including cerebral and cardiac vessels 1.
Risk Factors and Mechanisms
The increased viscosity and hypercoagulability associated with polycythemia may lead to an increased risk of thromboembolism or hemorrhage, especially in patients with underlying CH disease 1. The adjusted risk of 30-day postoperative mortality and cardiac morbidity begins to rise when hematocrit levels decrease to less than 39% or exceed 51% 1.
Management and Prevention
Management of polycythemia in patients with CH disease typically involves reducing the hematocrit through therapeutic phlebotomy, with a target hematocrit below 45% in most cases, as well as hydration therapy and sometimes cytoreductive medications like hydroxyurea, especially in secondary polycythemia or polycythemia vera 1. Addressing polycythemia is crucial for restoring normal blood flow and reducing the risk of stroke, transient ischemic attacks, and other cardiovascular complications associated with CH disease.
Key Considerations
It is essential to consider the individual patient's particular circumstances and tailor appropriate steps to reduce the risks associated with polycythemia, such as thromboembolism or hemorrhage, and to prevent complications in patients with CH disease 1. Current guidelines suggest that increasing numbers of risk factors correlate with increased risk, yet the risk was substantially lower than described in many of the original indices 1.
Clinical Implications
In clinical practice, it is crucial to monitor patients with CH disease for signs of polycythemia and to manage the condition promptly to prevent thromboembolic events and other complications, thereby improving morbidity, mortality, and quality of life outcomes 1.
From the Research
Risk Factors for Polycythemia Vera Related to Chronic Heart Disease
- Age is a significant risk factor for thrombosis in patients with polycythemia vera (PV) and essential thrombocythemia (ET) 2, 3, 4, 5
- Prior thrombosis is also a major risk factor for future thrombotic events in PV and ET patients 2, 3, 4, 5
- Other suggested risk factors for thrombosis in PV and ET include hypercholesterolemia, cigarette smoking, and apparent clonal hematopoiesis in younger patients 5
- The level of the platelet count per se does not correlate with thrombotic incidence in ET, but adequate control of the platelet count reduces the frequency of thrombosis 5
- In PV, adequate reduction of the hematocrit reduces the incidence of thrombosis 5
Management of Polycythemia Vera
- Therapeutic phlebotomy and low-dose aspirin are recommended for patients with low-risk PV 3, 4, 6
- Cytoreductive therapy with hydroxyurea or interferon alfa (IFN-α) is added for high-risk disease 2, 3, 4, 6
- Other disease features such as significant disease-related symptoms and splenomegaly, concurrent thrombocytosis and leukocytosis, or intolerance of phlebotomy can constitute an indication for cytoreductive therapy in patients with otherwise low-risk disease 6