Venous interventions achieving greater significance in the interventional world

298

Venous interventions, particularly stenting, thrombolysis and thrombectomy are achieving ever-greater significance in the interventional world, Gerard O’Sullivan, Department of Radiology, University Hospital Galway, Ireland, told Interventional News at the Cardiovascular and Interventional Radiological Society of Europe (CIRSE, 26– 30 September, Lisbon, Portugal).

“Venous thromboembolism is the third most common cause of cardiovascular mortality in the Western European world, after stroke and myocardial infarction. Venous thromboembolism, in Western Europe, causes more deaths than prostate cancer, breast cancer, AIDS and road traffic accidents combined, so it is a massive problem. At the moment, standard treatment is anticoagulation alone, but anticoagulation often leads to poor results in patients with iliofemoral deep vein thrombosis and we see a high instance of post thrombotic syndrome in these patients,” said O’Sullivan.

Shift in treatment

Commenting on the positive results of the CaVenT five-year data, O’Sullivan said: “With the CaVenT trial, a conservative trial, showing positive data for catheter-directed thrombolysis at five years and the ATTRACT trial (results awaited) building on the evidence base, there is likely to be a shift in the treatment of deep vein thrombosis with interest from medical device companies in new venous stents and thrombectomy devices. There is also a big shift towards intervening early in the disease process and often on an outpatient basis. However, all these patients will require a thrombectomy device and almost all of them will require a stent.”

Venous interventions are “a completely different animal” to arterial interventions

“Arterial intervention, which is the area that we have predominantly specialised in over the last 30 years, typically involves older patients who are smokers or diabetics who have risk factors for atherosclerosis. The primary pathology is the thickening of arterial walls and deposition of fatty plaques which leads to narrowing of the passage and eventually blockage. Despite the fact that the arteries are smaller, and because there is say 160mm of arterial pressure to push the blood through this vessel, generally all you have to do is to open up a tiny hole and the blood rushes through like a dam bursting. The venous system is completely different; it is a low pressure system, so it is like a slow moving river as opposed to a high pressure dam, and you need a much bigger channel as compared to the arterial circulation. So typically, say in a slim female weighing around 60 kilos, I would use an 8mm arterial stent; in that same patient I would use a 16mm venous stent. The patients are also different, as those with venous disease are usually much younger and do not have the “arterial” risk factors Most medical students are not taught about venous disease in this fashion, so while they are good at spotting patients with intermittent claudication (arterial) they are not good at recognising the symptoms of venous claudication. Most of my patients are young women. Usually after childbirth, they get a serious deep vein thrombosis and, after the initial period, their biggest symptom is weight gain. They cannot go for a run or even fast walk. Many cannot work if their jobs involve standing or walking. Eventually many get ulcers in their 40s, so it is not just ‘swollen legs’; it really does worsens their quality of life,” O’Sullivan said.

Venous stents are different

O’Sullivan then went on to differentiate between arterial and venous stents. “In terms of specific devices to treat venous disease, we need stents are larger diameter, longer in length, and with a higher radial force so that they are less likely to get compressed. They need to conform to the vessel wall rather than to try and straighten it, and they must be flexible enough to go across areas which involve flexion (e.g., the hip), and compression points such as the inguinal ligament; but most importantly they need to maintain these attributes for 30–50 years. So these devices need to be manufactured to a much higher level and subjected to incredibly high levels of stress testing. Where we are now is comparable to where coronary artery stenting was in 1989, at that time most patients went to coronary artery bypass grafting; nowadays the surgical option is reserved for those who are ‘un-stentable’. I think that the current state of venous stenting is comparable to that time, and therefore is in its infancy.”

Interim results of VIVO-EU announced

O’Sullivan presented the interim results from a European study of the Zilver Vena (Cook Medical) venous stent at the Cardiovascular and Interventional Radiological Society of Europe (CIRSE) 2015 meeting (26–30 September, Lisbon, Portugal). O’Sullivan is one of the principal investigators of the study, the others being Marta Ramirez Ortega (Madrid), Michael Lichtenberg (Arnsburg), Narayan Karunanithy (London) and Christoph Binkert (Switzerland).

VIVO EU is a prospective, non-randomised, multicentre study intended to evaluate the Zilver Vena stent in the treatment of symptomatic iliofemoral venous outflow obstruction. The study has reached full enrolment and three-quarters of patients have been followed for six months or longer. The study, sponsored by Cook Medical, has an intended one-year follow-up and patients are treated as per usual medical practice.

Thirty-five patients with symptomatic iliofemoral outflow obstruction were enrolled into the study. These patients had leg pain that limited their usual activity, swelling or skin discoloration in their leg. Site-assessed procedure outcomes showed that 45 stents were placed, which was an average of 1.3 stents per patient. Study physicians reported that all stents deployed as intended and no stent was scored as difficult to deploy, corresponding to a technical success, defined as successful delivery and deployment of the stent, of 100%.

Procedural success, defined as treated segment minimum lumen diameter ≥8mm at the end of the procedure and no major adverse events before discharge, was 94% (32/34), with one patient experiencing a pulmonary embolism before discharge. In the other patient who did not have a technical success, the stented minimum lumen diameter did not reach 8mm at the procedure end. “Further, in one patient, the caudal end of a stent was identified as landing in the obdurator vein instead of the common femoral vein on imaging one day post-procedure, and another stent was subsequently placed correctly after,” said O’Sullivan.

There were two major adverse events (n=35) with one clinically driven target lesion intervention for occlusion and one procedure- or device-related symptomatic pulmonary embolism. At the end of the procedure, Zilver Vena stent placement resulted in a more than two-fold improvement in the vessel minimum lumen diameter. Based on available follow-up data, stent placement has corresponded to improved clinical symptoms. The investigators observed that the Venous Disability Score improved following treatment, as did CEAP classification. VIVO-EU included patients/lesions that were representative of the real world population with iliofemoral venous outflow obstruction and Zilver Vena stent placement resulted in a greater than 100% luminal diameter improvement at procedure. Based on interim results, venous clinical symptoms improved following treatment, suggesting that the stent is beneficial to patients.

Zilver Vena was CE-marked in 2011 and its intended use is in the treatment of symptomatic iliofemoral venous outflow obstruction.

Importance of VIVO-EU data

“What the data show is that venous stenting works in an all-comer, real world population, not a cherry-picked population, and that stenting improved the diameter and resulted in improvement in clinical symptoms. It is early days yet, but there are several other trials that will likely report with the same message. There will soon be fairly consistent data that stenting opens the diameter of the ‘pipes’, and that patients with open veins do better,” O’Sullivan concluded.