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Exploring the Causes of Heparin-Induced ThrombocytopeniaInvestigator Renren Wen, PhD, is digging deeper into HIT to better understand why some patients, after heparin treatment, experience a drop in platelet counts, which is sometimes accompanied by life-threatening thrombosis.Oftentimes, to prevent clots or treat them after they develop, patients are treated with the blood thinner heparin, an effective and relatively low-cost medication that controls coagulation. But an estimated 30-50% of patients who take heparin can develop antibodies to the drug, with some experiencing adverse reactions that could lead to irreversible damage or loss of life. Some patients develop heparin-induced thrombocytopenia (HIT), a reaction to heparin treatment that occurs when an individual develops an antibody response to a complex formed between heparin and the platelet protein PF4 (PF4/H complex) that causes their platelet count to drop and, paradoxically, blood to coagulate. Patients diagnosed with HIT are typically taken off heparin immediately and are prescribed other anticoagulants. But these alternative medications are much more costly and can sometimes cause patients to experience even worse side effects, including life-threatening bleeding. Versiti Blood Research Institute Investigator Renren Wen, PhD, is digging deeper into HIT to understand what causes it and why, with a goal of finding better diagnosis and treatment options. Whereas a high percent of patients treated with heparin develop antibodies to PF4/H complex, only a subset of such patients develop HIT. Dr. Wen believes that B cells are the key to understanding why some patients develop HIT and others do not. B cells are an essential part of the body’s immune system that can react to antigens by generating antibodies. It has been thought that there are at least two types of PF4/H-binding antibodies – those that can activate platelets and are thus called “pathogenic” antibodies, and those that cannot activate platelets and are thus called “non-pathogenic” antibodies. To understand the difference between the “pathogenic” and “non-pathogenic” antibodies, Dr. Wen and her group cloned these two types of antibodies from HIT patients and observed that the “pathogenic” antibodies have structural signatures that distinguish them from the “non-pathogenic” ones. Dr. Wen believes that the cloned “pathogenic” antibodies and the associated structural signatures can be used to facilitate better understanding of the molecular pathogenesis of HIT and to develop novel diagnosis and treatment for HIT. “This could have the potential for better diagnosis and treatment of HIT,” she said. Dr. Wen often collaborates with other investigators who research HIT and treat patients with the disease, which helps propel lifesaving discoveries. “Versiti Blood Research Institute is a positive environment where people talk to each other and work together toward a common goal,” she said. Renren Wen, PhD, is an investigator at Versiti Blood Research Institute. Heparin-induced thrombocytopenia (HIT) is a life-threatening condition that can happen to some people after they take a medicine called heparin, a
blood-thinning drug that helps prevent clots. For some people, heparin triggers their immune system and causes a reaction where antibodies form and activate platelets -- tiny blood cells that
clump together to form clots and stop bleeds in your body. That can make blood clots more likely. When you have an immune response to heparin, it can lower your platelet count too far, a condition called thrombocytopenia. Heparin molecules bind with a protein to form something called heparin-PF4. When you have heparin-induced thrombocytopenia, your immune system sees heparin-PF4 as an
intruder and attacks it, setting off a chain reaction that leads to blood clots. There’s another type of HIT that doesn't have anything to do with your immune system. Nonimmune HIT isn't harmful, and it causes a mild dip in your platelet count. It happens to 10% of people with HIT. If you get it, your body will recover about 4 days after you stop taking heparin. It's also possible to have something called early-onset HIT. That's when HIT symptoms come within 24
hours after you take heparin. It might happen if you took heparin in the last few months, your body has HIT antibodies, and you're exposed to heparin again. You can also get HIT symptoms long after you stop taking the drug. Your doctor would call this delayed-onset HIT. It's very rare. Immune-induced HIT usually happens from 5 days to 2 weeks after you take your first dose of heparin. It can
cause your body to form dangerous blood clots like: These things happen in about 50% of people with HIT. Clots in the leg, lung, or heart can cause: Other signs of HIT include: Less often, HIT can put you at risk for heart attacks or strokes. In very rare cases, you could have a life-threatening
allergic reaction to heparin called anaphylaxis that can happen seconds or minutes after you’re exposed to it. Symptoms of that can include: If any of these things happen, call 911 right
away. Many things can make HIT more likely. Some you have no control over, including: Of course, taking heparin will raise your chances of HIT. You may need to take heparin as part of your treatment for several conditions, including some cardiovascular conditions. You might also get it when you have certain medical procedures, including: Lab tests can tell your doctor if you have HIT. Those tests include ones that let your doctor know about your: Your doctor may use something called the "4 Ts Score" to see if your symptoms look like HIT. The score takes into account: It's important to note that HIT symptoms can look very similar to another blood clot condition called vaccine-induced immune thrombotic thrombocytopenia (VITT). You can get this after you get some vaccines. Treatment Options for HITIf your doctor thinks you might have a reaction to heparin, they'll switch you to another blood thinner that won't cause HIT, including:
In addition to those blood thinners, you may also get a high dose of something known as intravenous immunoglobulin. That's a part of your blood's plasma that can help make your immune system stronger. Your doctor will keep an eye on your platelet count. After a few
days, once it returns to a safe range, they might switch you to another blood thinner called warfarin. You would take this by mouth. Depending on your health and how severe your HIT is, you may need to take warfarin for 1-3 months or
longer. Until recently, HIT was fatal for about 20% of people with it. Advances in treatments have dropped that number, but only to between 6% and 10%. So it's very important to get medical help as early as possible if you think you may have it. After you recover, your doctor may monitor your health and progress with routine checkups. That said, if you have HIT once, it may not mean you have an
allergy to heparin. The antibodies that cause the original reaction disappear from your body naturally about 3 months after you get treatment, and you may not have the same reaction again. But to make sure you don't get HIT again, talk with your doctor before you take forms of heparin or other types of
blood thinners. It’s also a good idea to share the details of when you had HIT, like: What can too much heparin cause?What happens if I overdose on Heparin (Injection)? Overdose symptoms may include easy bruising, nosebleeds, blood in your urine or stools, black or tarry stools, or any bleeding that will not stop.
What is the most side effect of heparin?The more common side effects of this drug include: bruising more easily. bleeding that takes longer to stop. irritation, pain, redness, or sores at the injection site.
What causes low heparin levels?The most common cause of heparin resistance is AT deficiency. The condition can be congenital and or acquired. Testing for the deficiency during the acute phase of illness while patient is on heparin infusion can be misleading.
How does heparin cause blood clots?What Causes HIT? For some people, heparin triggers their immune system and causes a reaction where antibodies form and activate platelets -- tiny blood cells that clump together to form clots and stop bleeds in your body. That can make blood clots more likely.
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