HOW I DO – DVT – Treatment – PART – 12
HOW I DO – DVT – Treatment – PART – 12
(All the articles published in past are available at www.shyamhemoncclinic.com/blog/)
Question: In last part, we covered some important points related to VTE (Deep Vein Thrombosis and Embolism) 1. Diagnostic evaluation should start before and in parallel to treatment. Especially certain tests like lupus anticoagulant are better collected before anticoagulation. 2. It is important to do basic work up for cancer, as it is one of the most important reasons not to miss. 3. Age appropriate cancer screening, not extensive cancer work up. 4. In about 80% cases, we do not find specific underlying cause. Even after extensive blood tests for hypercoagulable state. 5. Role of homocysteine in Indian setting. 6. No role for routine testing of hereditary thrombophilia tests in every patient. They are rare. And do not change treatment plan. Treatment plan is decided primarily by clinical factors, and some of the acquired risk factors.
Now that we have discussed work up before starting anticoagulation, can we discuss details of anticoagulation?
Answer: YES, now we are ready to discuss anticoagulation. Work up has been initiated and can continue in parallel. Treatment should not be delayed. I understand why most people are very anxious to start treatment, as DVT is potentially life threatening by leading to a pulmonary embolism. DVT of other sites like intestine, liver, brain etc can be life threatening by causing significant injury to the organ involved, or can lead to significant disability even if patient survives. Two most important factors in initial treatment are:
- How quickly anticoagulation is started
- More importantly how quickly optimal level of anticoagulation is achieved
Following is a reminder from our article Number 10 in this series “History – ensure patient does not have an absolute contraindication for anticoagulation e.g. recent intracranial bleeding, GI bleeding, ongoing bleeding, major trauma. Must check minimum CBC, PT, aPTT, Creatinine, SGPT. To ensure no severe thrombocytopenia, baseline coagulation abnormalities, major organ dysfunction.”
So now what choices do we have for anticoagulation: Intravenous heparin (unfractionated heparin); low molecular weight heparin (LMWH); Fondaparinux; warfarin or acitrom; NOAC (non vitamin k antagonist oral anticoagulants) e.g. dabigatran, rivaroxaban, apixaban.
Remember the two most important factors or goals of treatment as noted above: QUICKLY and OPTIMALLY.
Initial time is crucial as thrombus is likely still growing, and can lead to further organ injury or embolism. Hence as soon as diagnosis is known, anticoagulation should start. One should not wait for several hours. More so for embolism or visceral site thrombosis. For an uncomplicated DVT, a few hours is less likely to be critical.
The second point is even more critical i.e. how soon do you achieve optimal anticoagulation???
This is where LMWH scores much better over IV (Unfractionated) heparin. IV heparin has many sizes of heparin molecules, not uniform, hence it’s binding to Antithrombin (primary mechanism of action) is not very efficient. Whereas LMWH is made of fairly similar optimum size molecules. Hence binding to Antithrombin is much more efficient, leading to much faster achievement of optimal anticoagulation and very reliably. Once you start LMWH, you can expect adequate anticoagulation within few hours, if dose is proper for weight. For IV heparin, achievement of adequate anticoagulation can take several hours, many times over 24 hours, even with weight based nomograms. Also, one may have over anticoagulation i.e. too high aPTT. And if the adjustment in doses are not done well, there may be too high and too low aPTT. Also, for some patients even if dosing is done well, they have wide fluctuations in aPTT (just like some brittle diabetics, where glucose control is very difficult). For all these reasons, IV heparin is now rarely used as first choice. It has been extensively studied that long term outcome of DVT/PE correlates with how long it takes to achieve adequate anticoagulation in initial hours.
I still see some consultants want to use IV heparin if there is extensive thrombosis, thinking that “IV is stronger than subcutaneous”. IV heparin is clearly a suboptimal form of anticoagulation. It has limited applications, and has to be thoroughly followed up with proper aPTT monitoring to ensure not too little or not too high anticoagulation. We use IV heparin in some very limited situations today e.g. if patient is at high risk for bleeding due to thrombocytopenia, or recent surgery or recent major bleeding. Or LMWH dosing is difficult as patient has low GFR (high creatinine). With high creatinine, LMWH clearance is not clear, and there are no doses based on GFR. Hence there is risk of over anticoagulation. Monitoring is expensive, and not widely available (available in Ahmedabad) i.e. Anti Xa levels. Advantage of IV heparin in above noted situations is that one can titrate the anticoagulation to some extent by keeping a lower target for aPTT and most importantly, it can be reversed very quickly in case of bleeding using protamine. Protamine is widely available, as used in CABG surgery to reverse heparin post surgery. Also, simply stopping IV heparin reduces anticoagulation by 50% in one hour. LMWH on the other hand has a much longer half life, and antidote is not available or not very effective.
Ninety percent of patients of DVT/PE however can be treated with LMWH. Also, it allows outpatient treatment in very stable patients, and early discharge with home treatment.
June 15th 2025 Dr Chirag A. Shah; M.D. Oncology/Hematology (USA), 9998084001. Diplomate American Board of Oncology and Hematology. Ahmedabad. drchiragashah@gmail.com www.shyamhemoncclinic.com