First-in-human study finds novel laser technique “safe and effective” for embedded filter removal

William Kuo

The excimer laser sheath technique is safe and effective for removing embedded inferior vena cava (IVC) filters refractory to high-force retrieval, the investigators of a first-in-human escalation trial conclude in the Journal of the American Heart Association (JAHA). “This technique may allow cessation of filter-related anticoagulation and can be used to prevent and alleviate filter-related morbidity,” they write.

This is the largest study to date supporting a new indication for endovascular laser use to remove a variety of embedded IVC filters, regardless of implantation length.

Contextualising this research, lead author William T Kuo (Stanford University School of Medicine, Stanford, USA) and colleagues note that chronic indwelling IVC filters are associated with many potential risks, including non-thrombotic injury, thrombotic events, and the potential need for lifelong anticoagulation. While the US Food and Drug Administration (FDA) recommends that filters be promptly removed once the risk of acute pulmonary embolism has subsided, many filters remain chronically implanted and become refractory to standard retrieval methods. More advanced retrieval techniques (defined as any method other than standard snaring and sheathing) may be effective, but can induce major procedure-related complications due to the use of excessive force. This first-in-human study reports that these complications can be avoided with the use of the excimer laser sheath technique.

Over an 8.5-year period, 500 patients were prospectively enrolled into the study. There were 225 men and 275 women (mean age, 49 years; range, 15–90 years). Indications for retrieval included symptomatic acute inferior vena cava thrombosis, chronic inferior vena cava occlusion, and/or pain from filter penetration. Retrieval was also offered to prevent risks from prolonged implantation and potentially to eliminate the need for lifelong anticoagulation. In total, there were 140 physically symptomatic patients (28%; 140 of 500) with filter-related morbidity, 360 physically asymptomatic patients with filter-related anxiety (72%; 360 of 500), and 78 patients (16%; 78 of 500) receiving filter-related anticoagulation with no underlying thrombophilia.

After retrieval failed using standard retrieval force (6–7lb via digital gauge), treatment escalation was initiated by placing a laser sheath (Spectranetics) connected to a 308-nm XeCl excimer laser generator (CVX-300, Spectranetics), to attempt fibrotic tissue ablation. “We hypothesised that the laser-assisted technique would allow retrieval of more than 95% of embedded filters with less than 5% risk of major complications and with lower force,” Kuo et al put in their abstract.

The three primary study end points were: successful filter retrieval (complete filter detachment from the caval wall and removal from the body, excluding extravascular filter fragments) versus failure; presence versus absence of major procedure-related complications; and the difference in force applied to a patient’s filter both with and without laser assistance during attempted filter removal. Secondary end points were defined as follows: resolution of symptoms in patients with filter-related morbidity, resolution of filter-related anxiety, and further need for filter-related anticoagulation. The primary outcome was successful filter retrieval, and the primary safety outcome was any major procedure-related complication as defined by established guidelines.

Laser-assisted retrieval was successful in 99.4% (497 of 500; 95% CI, 98.3–99.9%). This was significantly higher than the 95% hypothesised by Kuo et al ahead of the study’s initiation (p<0.0001). Three cases that failed retrieval did so because of bulky calcified thrombus (refractory to thrombectomy) within cylindrical-shaped filter components, creating a volume that was too large to be captured within the bore of the existing laser sheath apparatus, the authors explain.

The mean filter dwell time was 1,528 days (4.2 years; range, 37–10,047 days [>27.5 years]), and the median dwell time was 569 days (interquartile range, 260–2,348 days). Successful filter retrieval alleviated filter-related morbidity in 98.5% of cases (138 of 140; 95% CI, 96.5–100%) and allowed cessation of anticoagulation in 98.7% of cases (77 of 78; 95% CI, 93.1–100.0%).

Furthermore, the major complication rate was low: 2% (in 10 of 500 patients; 95% CI, 1–3.6%), with only 0.6% complications from laser. This is significantly less than the 5% threshold (p<0.0005). All complications were successfully treated with either medical management and/or percutaneous endovascular therapy without the need for open surgery.

Discussing the ten complications observed over the study period, Kuo et al say: “As a specialised centre that accepts complex filter cases, our patients were often referred after failed retrieval attempts or when other centres refused to attempt filter removal because of high procedural risks. Indeed, we noted increased variety and complexity of cases encountered throughout the study period. We believe this helps to explain why 10 different combinations of major complications and causes were encountered without duplication. For instance, we accepted cases involving severe filter fractures and penetrations that increased the risk of injury to the IVC and/or adjacent arteries during filter removal. In attempting these cases, we learned that severe filter fractures may lead to asymmetric lasing of fibrous tissue along the vessel wall causing major venous haemorrhage. We also learned that filter components may penetrate through the cava and into adjacent arteries predisposing to organ infarction, major arterial haemorrhage, and arteriovenous fistula formation during filter removal.”

In addition to perhaps seeing more complex cases, another consequence of conducting this study at a single centre specialised in advanced filter removal is that “It is unclear whether the overall safety and efficacy of removing embedded filters as described here [in JAHA] would translate into similar outcomes when performed elsewhere,” as the authors put it. They list this as a limitation of the study, alongside the fact that, although all patients with anxiety reported relief of this symptom, the investigators did not obtain formal psychiatric evaluations or use scoring systems to quantify their anxiety relief post procedure.

Kuo et al also call for a cost analysis study, musing that, although the laser sheath apparatus carries additional device cost, successful filter removal in a single session may decrease overall expense by eliminating the high cost of multiple failed procedures routinely observed before successful laser retrieval.

The laser sheath apparatus is currently not FDA-approved for IVC filter removal; this is an experimental protocol—albeit one that has now been validated in a large cohort of patients.


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