Despite 20 years of cardiovascular surgery practice, I had been uncertain of how to best answer my patient’s question…until now.
There is increasing evidence that we can tailor blood thinning medication treatment for an individual patient who has had a blood clot in their vein. The American College of Chest Physicians (ACCP) has just updated its 9th edition of the guidelines for Antithrombotic Therapy and Prevention of Thrombosis. The above referenced guidelines allow your doctor to use several new recommendations so as to develop an anticoagulation management plan for you.
Deep venous thrombosis (DVT), whether manifest in an extremity or in the lungs, now should be viewed as either an “unprovoked”or a “secondary” event. An unprovoked episode generally occurs in a healthy individual without increased risk factors for forming blood clots. If this is the case, your doctor will order blood tests and occasionally x-rays to determine if an underlying cause for your blood clots can be found.
A secondary blood clot event is associated with conditions that range from post trauma, stroke, major orthopedic, abdominal, pelvic, and neurosurgical procedures to medical states that are expected to eventually resolve or abate. (eg. pregnancy, inflammatory bowel disease, active malignancy, intravenous lines, major pneumonia). These conditions are all well known risk factors which predispose an individual to develop blood clots in their veins. To that end, if we divide blood clot events into these two categories we can make a clear recommendation of anticoagulation duration for our patients.
A patient thought to have an unprovoked DVT should be investigated for having an acquired or inherited predisposition to developing clots in veins. If one of these predisposing conditions is discovered by your doctor, a recommendation for prolonged use of ablood thinner medication is likely.
However, if nothing is found as to cause, after 3 months of anticoagulation, an ultrasound (sound wave) exam of the extremity should be performed. If the ultrasound is now normal,you can be taken off of blood thinners. Four weeks later, a blood test (“D-dimer”) should be analyzed to help determine the risk ofblood clot recurrence. An elevated D-dimer suggests you would benefit from continuation of anticoagulation (blood thinners)…at least for another 3 months. Even if all indicators are found negative, the unprovoked DVT patient has a known increased risk of recurrent blood clots in veins due to factors that as of yet we doctors have not been able to identify. A recommendation for life long blood thinners in this group is a tough call. We usually do not recommend this after the first episode. A second blood clot episodewould trigger a life-long anticoagulation recommendation.
In secondary DVT, after three months of blood thinners, an ultrasound should also be performed. If this ultrasound shows a persistent vein blockage from old clot (at least 40% narrowing), a higher risk of blood clot recurrence exists compared to an ultrasound without any residual vein blockage. It is usually not recommended to stop anticoagulation if a blockage is seen on ultrasound except if a patient is at a high risk for internal bleeding (eg. history of stomach ulcers). In fact, a vein blockage of greater than 50% may warrant placement of a metal stent into the vein to open it up. Generally, a normal ultrasound after 3 months of treatment with resolution of any precipitating/provoking risk factors predicts a small chance for blood clot recurrence. If the ultrasound is indeed now normal and those risk factors for forming blood clots have passed, anticoagulation can be stopped. Blood tests are also frequently ordered four weeks later.
Patients with DVT and under treatment for cancer are a difficult group to advise as to duration of anticoagulation. Usually, upon completion of cancer treatment and in the presence of cancer remission is when anticoagulation can be stopped.
In summary, anticoagulation can be concluded after 3-6 months in most patients with a first DVT. Ultrasound tests, the D-dimer blood test and the medical history surrounding the patient should be used to help your doctor decide when to stop blood thinner therapy.
I hope this summary helps. Please feel free to contact our practice for questions.
Gary Dworkin, MD
