Clot Chronicles: Unprovoked vs. Provoked VTE

Hi, my name is Greg Piazza, and I’m one of the faculty at Brigham and Women’s Hospital Division of Cardiovascular Medicine, one of the members of the board of directors for the North American Thrombosis Forum, and the Education Chair for the organization. I want to welcome you to Clot Chronicles. 

This morning, we’re going to be talking about the distinction—or lack thereof—between provoked and unprovoked venous thromboembolism (VTE). For quite a while, we’ve been dividing deep vein thrombosis (DVT) and pulmonary embolism, or PE, into two distinct categories: provoked (where there’s an identifiable trigger for the blood clot) and unprovoked (where the blood clot just happens out of the blue). The problem with that distinction is that it’s not black and white, and sometimes there’s a very artificial difference between the two. 

There are a number of patients who have provoked VTE but have risk factors that aren’t transient; they’re persistent provoking or persistent predisposing factors that increase the patient’s risk for a DVT and PE even after they get through the initial treatment of a blood clot. So, you could imagine a patient who’s undergoing total hip replacement and suffers a blood clot; the hip replacement is a surgery and a clear provoking factor, and we would treat that for a limited amount of time with anticoagulation (or blood thinners). 

Now, if we consider that very same patient and add to their problem list inflammatory bowel disease, like ulcerative colitis or Crohn’s disease, plus obesity, smoking, and maybe some mild kidney disease, now we have a number of predisposing permanent risk factors that won’t go away after the patient recovers from their total hip replacement. And, as such, the patient may be at higher risk for recurrence than someone who doesn’t have those persistent provoking or predisposing factors. 

You can see that it’s not really black and white and the field of VTE is starting to move away from this artificial distinction between provoked and unprovoked. We know that patients with unprovoked VTE have a high risk of recurrence and we tend to provide those patients with long-term anticoagulation to lower that risk. But now we’re starting to realize that there are patients who have provoked VTE but a number of risk factors that don’t just miraculously go away, and they may also benefit from extended-duration preventive measures.

There was a study called EINSTEIN CHOICE published a few years ago that actually showed that even in a population of patients where 60% suffered provoked VTE, continuing blood thinners for a longer period of time actually was very protective for those patients. So, I can envision—and a lot of experts in the field feel—that in the future, we probably will be considering individual risk factors and other comorbidities in patients rather than just splitting them into two groups of provoked and unprovoked. We’ll use the risk profile of the patient on an individual basis to make decisions about how long they should be on blood thinners. So, I think what we’re moving towards is a more precise type of medicine and treatment for patients with DVT and PE. 

Thank you for joining Clot Chronicles.

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