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Assessing Cardiovascular Risk in Essential Thrombocythemia

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Published on June 1, 2021

How Is Cardiovascular Risk Assessed in Patients with ET?

How is cardiovascular risk assessed in patients with essential thrombocythemia (ET), and what are the treatment options? Follow along as Jeanne Palmer, MD, from Mayo Clinic Arizona explains some of the standard risk factors such as blood pressure, diabetes, cholesterol, and family history, and how they can inform treatment choice. Dr. Palmer also discusses aspirin dosing and how it is managed.

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Transcript | Assessing Cardiovascular Risk in Essential Thrombocythemia

How Is Cardiovascular Risk Assessed in an Essential Thrombocythemia (ET) Patient?

Dr. Palmer: When I'm assessing somebody with essential thrombocythemia (ET) or any myeloproliferative disease, I really want to understand what their cardiovascular risk is. When I look at somebody's cardiovascular risk, I look at some of the standard risk factors, such as blood pressure, diabetes, as well as cholesterol. And also, a family history of early coronary artery disease or strokes is a very helpful thing to know. Any of these factors or any combination of these factors can contribute to the cardiovascular disease risk, which will subsequently help me decide how aggressively to cytoreduce somebody with essential thrombocythemia. Or whether I can do something like phlebotomy for a patient with polycythemia vera (PV), or whether they require cytoreductive therapy. It's not a clear guideline of how to do it. There's not like, well, if you have two risk factors, therefore you're higher cardiovascular risk, and we do X, Y, or Z. It's more of a gestalt when talking to somebody of what risk factors they have.

The other thing with cardiovascular risk that's very important is how well somebody is controlling it. If they are taking the appropriate medications to control their cardiovascular risk if they're exercising regularly and eating a healthy diet. I sometimes feel like essential thrombocythemia is a great way to remind somebody how to take care of themselves because it provides a reason to engage in these healthy lifestyle choices, which sometimes people aren't able to do. So, in addition to just having the risk factors, is also a matter of how well somebody takes care of themselves and controls these risk factors. 

What Factors Are Considered When Dosing Aspirin?

Aspirin is a drug that we frequently employ in patients with myeloproliferative disease. It has a very strong anti-platelet effect that can help prevent thrombotic events. The dosing of aspirin, however, is something that has been widely discussed throughout the MPN community. The standard dosing of baby aspirin is 81 milligrams a day. This is the dose that I generally recommend to patients. There have been investigations that show that with the half-life of aspirin, twice-daily dosing probably maintains a better concentration of aspirin in someone's blood over time. I don't know that there's necessarily a greater benefit to having aspirin twice a day. However, in patients that have a lot of microvasculature symptoms, such as numbness and tingling in the hands, headaches — these are patients that often will benefit from having increased doses of aspirin. And I've even had patients take up to three aspirin a day to try to help control those symptoms.

The one situation where aspirin is not advised to use in essential thrombocythemia is in the case where somebody has a secondary von Willebrand's deficiency (VWD). Von Willebrand’s is one of the first proteins that gets into play when starting a blood clot. So, when you cut yourself, the von Willebrand is critical to forming the initial blood clot to prevent you from continuing to bleed. Platelets have von Willebrand receptors on their surface, therefore they hold onto von Willebrand's factor. If you have a very high number of platelets or someone has a high number of platelets, what ends up happening is the platelets sort of soak up the von Willebrand's factor, just like a sponge soaks up water. So, therefore there's not enough von Willebrand factor in the blood circulation to actually help stop bleeding when somebody gets a cut or if somebody has a nosebleed. In those settings, we can determine that by looking at a von Willebrand's factor in the blood. And when somebody has a low von Willebrand's factor, number one, that is a reason that I would cytoreduce someone or bring their blood counts down, their platelet count down.

And the second thing is, is I hold the baby aspirin, especially while they have a decreased von Willebrand’s activity level in their blood. The other thing that von Willebrand’s does as a secondary effect that can cause even more serious bleeding occurrences, is that von Willebrand’s is a protector for factor VIII. So, if you do not have von Willebrand’s in your blood to help protect factor VIII, it kind of cocoons it. If you don't have the von Willebrand's factor ready to cocoon that factor VIII, the factor VIII can be readily destroyed, in which case that even has a greater risk for bleeding. Factor VIII is one of the clotting factors and the primary clotting factor that is missing in patients with hemophilia. So, if you've heard of the hemophiliac, that is what happens when you don't have a lot of factor VIII. So, the bleeding complications associated with essential thrombocythemia are important to recognize because aspirin will just augment those bleeding complications that can occur.