We had an interesting discussion on Calf DVT at conference this morning. Wanted to share some papers on calf DVT management that may help guide your practice. Here are two recent papers discussed in emrap Paperchase, which gives a to the point summary, from May & Feburary this year looking at management vs. risk of calf DVT management.
Feburary 2017 (The May 2017 is below and follows up on this with another study)
Paper Chase 2 - Calf Clot Demystification
Sanjay Arora MD and Michael Menchine MD
Take Home Points
❏ Therapeutic anticoagulation for isolated calf DVT is associated with a reduction in proximal DVT extension and pulmonary embolism but increased risk of bleeding.
❏ Patients should be given anticoagulation for isolated calf DVT unless they have increased risk of bleeding or very low risk features.
❏ The number needed to treat to prevent clot extension or PE is 16.
● Utter, GH et al. Therapeutic anticoagulation for isolated calf deep vein thrombosis. JAMA Surg. 2016 Sep 21;151(9):e161770.PMID: 27437827
● The bottom line: therapeutic anticoagulation for isolated calf DVT was associated with a reduction in proximal DVT extension and pulmonary embolism but with increased risk in bleeding. The study supports anticoagulating patients with calf DVT unless they have very low risk features or high bleed risk.
● Sometimes the work-up for DVT identifies clot in the calf (the veins distal to the knee). It is important to know whether your ultrasound tech actually is looking in the calf. You may have to tell them to look there as it is not routine. How should these be managed?
● This is a common problem and there are few studies available to guide therapy. Those who support anticoagulation cite increased risk of pulmonary embolism. Those against anticoagulation say clot progression and subsequent pulmonary embolism is rare.
● This was a single center, retrospective cohort study which reviewed all lower extremity venous duplex ultrasounds over a 3 year period and identified patients with isolated DVT to the calf. They excluded patients with chronic DVT or prior diagnosis of pulmonary embolism. This was not a randomized controlled trial. Anticoagulation was determined by the physician. Anticoagulated patients were grouped together regardless of agent used.
● They looked at the rate of DVT and PE as well as safety. 697 patients with isolated calf DVT were identified from over 14000 lower extremity venous duplex studies. 313 patients were excluded leaving 384 patients. 243 patients (63%) were anticoagulated and 141 patients were not.
● 5% of the control group developed proximal DVT compared to 1.6%. 4.3% of patients developed a PE in control group compared to 1.6% in the anticoagulated group. Combined, the absolute difference was 6 with a number needed to treat of 16.
● What was the number needed to harm? 2.6% of controls experienced bleeding compared to 8.6% of the anticoagulated group. These groups were different at baseline but additional analysis determined it probably didn’t affect results. It is possible increased testing in the control groups led to increased identification of clots.
● What does this mean? You need to consider the risk of bleeding. However, if the patient is symptomatic and you found a distal DVT, just treat them like a proximal DVT and give them anticoagulation. If they are asymptomatic or the clot is an incidental finding, you can either give them anticoagulation or if they are very low risk (small clot, very distal to the knee, no risk factors like cancer or prolonged immobilization) you could consider surveillance on these patients and repeat the study in two weeks and defer anticoagulation pending progression.
● The recent 2015 CHEST guidelines recommended serial imaging over two weeks rather than anticoagulation for acute isolated distal DVT without severe symptoms or risk factors for progression. This is not just repeat study in two weeks but rather surveillance over two weeks. If there are severe symptoms or risks factors for extension, the guidelines recommend anticoagulation over serial imaging.
○ What is high risk? Cancer or unprovoked clot.
○ Kearon, C et al. Antithrombotic therapy for VTA disease: CHEST guideline and expert panel report.Chest. 2016 Feb;149(2):315-52.PMID: 26867832
Paper Chase 4 – CACTUS and The Calf Clot
Sanjay Arora MD and Michael Menchine MD
Take Home Points
▪ Anticoagulation of low risk patients with isolated calf DVTs results in higher bleeding risk without measurable clinical benefit.
▪ Bleeding occurred in 4% of the anticoagulated group.
● Righini, M et al. Anticoagulant therapy for symptomatic calf deep vein thrombosis (CACTUS): a randomised, double-blind, placebo-controlled trial. Lancet Haematol. 2016 Dec;3(12):e556-e562. PMID: 27836513
● The bottom line: anticoagulating low risk patients with isolated calf DVTs resulted in a higher bleeding risk without measurable clinical benefit.
● We recently discussed a paper on the topic of DVT of the calf. This is a common problem. Benefits to anticoagulation include possible decreased risk of pulmonary embolism in the future. However, very few of these clots propagate and if they do, it usually happens within a few weeks. It may be better to watch and wait.
o The prior paper suggested most should be treated if they are symptomatic unless they have low risk features. However, it was not randomized controlled trial.
o Utter, GH et al. Therapeutic anticoagulation for isolated calf deep vein thrombosis. JAMA Surg. 2016 Sep 21;151(9):e161770.PMID: 27437827
● This was a study spread out over 23 centers in 3 countries of patients and included patients with a clot in the deep veins distal to the popliteal vein (not the superficial veins). Patients with chronic DVTs, recent DVT or PE, contraindications to anticoagulation, current anticoagulation and pregnant patients were excluded.
o Patients were randomized to injections of nadroparin (a subcutaneous factor Xa inhibitor) or placebo for 42 days.
o The primary efficacy outcome was a composite endpoint of extension of the calf DVT to the proximal veins, contralateral proximal DVT or symptomatic pulmonary embolism at day 42.
o They enrolled a total of 259 patients over 6 years.
o They looked at a primary safety outcome was bleeding.
● What did they find?
o The primary composite efficacy outcome was 3% in anticoagulated patients and 5% in placebo. This is a nice reminder that the overall progression rate in this study was low in patients who were followed very closely and received a follow-up scan. No one in either group died from pulmonary embolism.
o Bleeding occurred in 4% of the anticoagulated group and 0% of the placebo group.
● What does it mean? These results are in contrast to most of the previous opinion pieces and observational data favoring treatment. They suggest extension is rare. Treatment has minimal impact and can result in clinically significant bleeding. Serial ultrasound is ok for asymptomatic patients and low risk patients with a symptomatic clot.
● There is still no guidance on high risk patients. They should likely be treated unless there is a contraindication to anticoagulation.
● If a clot is going to propagate, it will do so quickly. If you are sending these patients home, make sure they have follow-up within two weeks.