HOW I DO – DVT – Treatment IVC Filter; Oral Anticoagulants – PART – 14

HOW I DO – DVT – Treatment IVC Filter; Oral Anticoagulants – PART – 14

(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. LMWH is clearly superior to regular heparin (UFH). LMWH dosing is weight based, hence important to dose properly. 2. Role of CDT – catheter directed treatment i.e. thrombolysis at site of thrombus directly, and/or mechanical extraction of clot. Useful in cases of massive pulmonary embolism (with severe pulmonary artery hypertension, or significantly raised Pro BNP), massive DVT especially not responding to anticoagulation rapidly or optimally. CDT can be done up to  7-14 days post DVT/PE.

Are there any other procedures in treatment of DVT/PE.

Answer: YES. Much older procedure is IVC filter placement, and occasionally SVC stent as well. IVC i.e. Inferior Vena Cava filter placement is a very old procedure. Idea is to put a filter in IVC, which prevents a large embolus from going to heart. When I was in study, this used to be much more popular, as it was fairly new and idea seemed very logical. Like many new technologies however, further research showed that it did NOT lead to improvement in overall survival. Means, yes you do prevent large emboli from traveling to heart in the short term, but that did not translate into a major long term benefit. Perhaps because the filter itself became a source for thrombosis formation (both in IVC and in lower extremity), embolism and few other complications such as IVC injury. Additionally, presence of filter meant need for life long anticoagulation. This however is not very clear.

Means current recommendations for use of IVC filter are very few, and it is used much less commonly. Also, most filters are removed after about 14 to 28 days, once the acute risk of a major embolism is over. Unlike in the past, when most IVC filters were not removed.

Que: Interesting. It seems very logical that IVC filter would be a very good thing to do, but data is not in favor. And hence now used rarely. So, when do you advise IVC filter?

Ans: We had a patient in ICU few months ago, referred to us for thrombocytopenia. This patient also developed a DVT. With platelets below 30,000, anticoagulation was not feasible. We advised IVC filter in this patient.

So, indications are: 1. A patient like above where anticoagulation is not possible. Absolute contraindication due to any reason e.g. low platelet, recent major bleeding or trauma or surgery etc.

2. A patient where cardiopulmonary reserve is very low, and an embolism first or second is likely to be fatal. For example, someone with very low ejection fraction, or very poor lung reserve.

Que: This is very clear. Limited but important indications where IVC filter is useful. Coming back to more common issue i.e. oral medicines to treat DVT/PE. We have had only warfarin and acitrom for many years, requiring regular monitoring of prothrombin time. And these also have significant drug interactions, as well as, food interactions. But now we have new oral anticoagulatns, known as NOAC or DOAC. These do not require monitoring by PT test. Then why do we still need warfarin, acitrom?

Ans: Well, new drugs certainly have added options for our patients. But no drug is perfect for all situations. For large majority of patients, NOAC (apixaban, rivaroxaban, dabigatran etc) are equal or better. But for some indications, warfarin or acitrom are better. These include:

1. Low GFR (high creatinine). NOAC dose adjustment is difficult with very low GFR. It requires testing of anti factor Xa activity level. This test is not widely available, and is expensive. It is available in Ahmedabad, however, it is still not easy to adjust dose for very low GFR.
2. APLA positive patient i.e. antiphospholipid antibody syndrome and thrombosis. Efficacy of warfarin here is better compared to NOAC, especially with double or triple APLA positive patients. We have an active patient with triple APLA now where we are using warfarin.
3. Mechanical heart valve – acitrom or warfarin is clearly better compared with NOAC. 4. Severe liver disease

Other than these indications, practically for all patients with DVT/PE, NOAC are preferred. Efficacy is same as warfarin, Bleeding rates are slightly better. Fixed dose for adults patients can be given without any test to measure intensity of anticoagulation. This is very useful in India, as reliable PT monitoring is not available for many patients. Even within city, laboratory quality is variable.

PT test has been standardized with use of INR i.e. international normalized ratio. This ratio is used to correct variations in laboratory reagent. Means absolute value of PT cannot be compared between two different reagents. But INR takes care of this variation. Most patients need to maintain INR between 2 to 3. Another important aspect in patients on warfarin or acitrom is diet. Many myths around this topic e.g. patients should not take any leafy green vegetables etc which are rich in vitamin K. Fact is, patients can take all such foods. Only they should avoid large variations in diet e.g. fasting for several days, or staying on only certain vegetables for several days etc. With stable dietary pattern, dose is adjusted. When they need antibiotics or other medicines for more than a week, they should ensure INR is still within range. Drug interactions of many kinds, and changes in gut bacteria from antibiotics can alter INR balance. August 13^th 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