CHICAGO (FRONTLINE MEDICAL NEWS) – Caval extension of an acute iliofemoral deep vein thrombosis paradoxically portends better treatment outcomes than does thrombolysis of a DVT without involvement of the inferior vena cava, according to Rabih A. Chaer, MD, professor of surgery at the University of Pittsburgh.

This finding from a retrospective analysis of the University of Pittsburgh experience might seem counterintuitive. After all, caval extension clearly indicates a greater clot burden. One possible explanation: Clearing a thrombus from a large vessel, such as the inferior vena cava (IVC), provides an added protective effect. Also, since the caval segments don’t have valves – their flow is based upon negative pressure in the chest – they may not contribute as much to postthrombotic morbidity to the same extent as do thrombosed iliofemoral segments, Dr. Chaer speculated at a symposium on vascular surgery sponsored by Northwestern University.

In addition, patients with caval extension were treated more aggressively: 98% of them underwent pharmacomechanical thrombolysis with the Angiojet or another device as an adjunct to catheter-directed thrombolysis, compared with 82% of noncaval patients.

The impetus for Dr. Chaer and coinvestigators to review the Pittsburgh experience was a lack of clarity in the literature as to the effect IVC thrombosis has on thrombolysis outcomes in patients with acute iliofemoral DVT. Even though caval thrombus extension is present in up to 22% of patients with iliofemoral DVT, current guidelines issued by the American College of Chest Physicians, the American Heart Association, and the Society for Vascular Surgery don’t address the distinction between iliofemoral DVT with and without IVC extension in regard to the occurrence of postthrombotic syndrome (PTS), the most common complication of DVT.

The incidence of PTS in patients whose iliofemoral DVT is treated by anticoagulation and compression alone is up to 50%. Mounting evidence indicates that catheter-directed thrombolysis and pharmacomechanical thrombolysis aimed at achieving early thrombus removal and symptom relief help maintain valvular competence and reduce the risk of PTS, the surgeon noted.

PTS is diagnosed using the validated Villalta scale , which incorporates clinical signs including pain on calf compression, skin edema and redness, and ulcers, as well as symptoms such as leg cramping, heaviness, itching, and paresthesia.

The Pittsburgh series included 102 consecutive patients treated with various combinations of catheter-directed or pharmacomechanical thrombolysis in 127 limbs with acute iliofemoral thrombosis. In 46 patients, the thrombus extended into the IVC, all the way up to the renal veins in most cases.

The groups with and without caval extension were similar in terms of age and prevalence of malignancy, hypercoagulable state, and clot age. However, a history of previous DVT was significantly more common in the group with IVC thrombus. Also, more than 60% of patients with caval extension got an IVC filter, a rate more than 10-fold greater than that in patients without caval extension.

In this series, caval thrombosis had no effect on the technical success of thrombolysis. The technical success rate –defined as at least 50% clot lysis – was 89% in both groups. Rates of recurrent DVT within 30 days were similar in the two groups as well: 11% in the caval thrombosis group and 14% in the noncaval group. At 2 years postintervention, 77%-78% of patients in both groups remained free of DVT recurrence. The rate of PTS – defined by a Villalta score of 5 or more – at 2 years was 34% in the noncaval group, which was significantly higher than the 11% rate in patients with IVC thrombus extension. Ultrasound-identified valve reflux was present in 51% of the noncaval group at 2 years, compared with 51% of the noncaval group.

On multivariate analysis, incomplete clot lysis was associated with nearly a 23-fold increased risk of recurrent DVT and a 5.6-fold increased risk of PTS. Caval involvement was independently associated with a 78% reduction in PTS risk.

The Society for Vascular Surgery’s guidelines recommend pharmacomechanical thrombolysis over catheter-directed thrombolysis if the expertise is available. The Pittsburgh experience speaks to the worth of that recommendation.

“Pharmacomechanical techniques can be advantageous. They can expedite the lysis process by clearing most of the clot. In our series, 20 patients were treated with pharmacomechanical techniques in a single session,” Dr. Chaer noted.

The use of IVC filters in the setting of caval extension of iliofemoral DVT is controversial, according to the surgeon: A thrombus that gets trapped in the filter is tough to remove, precluding successful recanalization.

“One-third of the patients in our series got a filter, but we’ve become more conservative nowadays. We don’t use filters anymore. But I think those patients who might benefit from an IVC filter are those who present with a PE [pulmonary embolism], because that’s telling you they might develop another PE, as well as those patients in whom pharmacomechanical thrombolysis is anticipated because we’ve seen that those patients are also more likely to develop a PE,” he said.

The University of Pittsburgh study on the effect of IVC thrombus extension has been published ( J Vasc Surg Venous Lymphat Disord. 2016 Oct;4[4]:385-91 ).

Dr. Chaer reported serving as a paid speaker for Boston Scientific.

SOURCE: Chaer RA. Northwestern Vascular Symposium 2017.