Systematic review deems coated stents plus SAPT feasible in ruptured aneurysms

A systematic review and meta-analysis of the “scarce” existing literature has adjudged flow diversion with a coated stent plus single antiplatelet therapy (SAPT) to be “feasible” in the treatment of ruptured intracranial aneurysms, despite thromboembolic complications occurring in a “significant number of patients”— all of which were associated with aspirin-based SAPT.

THESE FINDINGS HAVE BEEN published in World Neurosurgery by Matthias Gawlitza (University Hospital Leipzig, Leipzig, Germany) and colleagues, who also note a low rate of haemorrhagic complications across the patient cohort involved.

At the outset of their report, the authors state that, owing to the increased risk of major bleeding events in patients with ruptured aneurysms who undergo flow diversion alongside dual antiplatelet therapy (DAPT), surfacemodified flow diverters that can be implanted with SAPT would represent “a major step forward” in this setting.

“Flow diverters coated with antithrombogenic substances were recently introduced and have shown encouraging results in the preclinical setting,” Gawlitza et al further note.

“Our aim was to analyse their clinical application in patients with ruptured intracranial aneurysms using SAPT.”

The authors also highlight three surface-modified or ‘coated’ flow diverters designed to reduce thrombogenicity that have gained CE-mark clearance, and are currently under “intensive clinical and scientific investigation”—the Pipeline Embolisation Device (PED) Shield (Medtronic), equipped with a phosphorylcholine coating, and the P48 hydrophilic coating (HPC) and P64 HPC flow-modulation devices (Phenox/ Wallaby Medical).

“Hydrophilic polymer and phosphorylcholine coating for flow diverters are major technical advances with encouraging preclinical data proving reduced thrombus formation, both in vitro and in vivo,” they add. “Quickly after market launch, the first case reports and small series about their use in ruptured aneurysms under SAPT were published, specifically addressing their potential to reduce complications associated with DAPT in critically ill patients with SAH [subarachnoid haemorrhage].”

With these devices as their central focus, Gawlitza et al set out to assess the safety and efficacy of flow diverters coiling was performed to achieve complete occlusion, resulting in an overall, immediate complete occlusion rate of 94.3%. The final complete occlusion rate at 90–180 days was 93.2%, the authors add, noting that this core laboratory-rated rate of occlusion is “slightly higher than previously published occlusion rates on endovascular embolisation of DAVFs”. with antithrombogenic coating in the treatment of ruptured aneurysms under SAPT. To do this, they performed a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant systematic review and meta-analysis covering three major databases up to March 2022.

Regarding functional outcomes, Möhlenbruch and colleagues report that—after a mean follow-up of 5.5 months—the modified Rankin Scale (mRS) score was stable or improved 93% of the time. However, a worsening mRS score was deemed to have been related to the procedure in one patient (1.8%).

“Squid, which features several modifications compared with the established agent, Onyx, expands the armamentarium of liquid embolic agents for the treatment of DAVFs,” they continue.

Despite this, the authors also point out that, even with these potential advantages in mind, impedance of a plug formation; early distal embolisation; and a potentially higher ability to diffuse into collateral meningeal arteries, constitute three major drawbacks associated with embolisation utilising low-viscosity agents. And, while none were directly observed in the LIQUID study, these drawbacks should be known and considered by interventionists using Squid 12.

Möhlenbruch and colleagues go on to briefly acknowledge their study’s limitations, including a relatively low number of patients, the fact that 9.3% of patients did not have data available for follow-up, and the lack of a control group involving other embolic agents. As such, while they claim that this is the largest study reporting on DAVF embolisation using Squid to date—and the first ever prospective study on the endovascular treatment of high-grade DAVFs in “the era of liquid embolic agents”—the scope for comparisons between Squid and other agents is limited.

Five studies reporting 43 patients with a total of 46 intracranial aneurysms were identified and deemed eligible for inclusion in the analysis. The authors also note that more than one stent was implanted in 16% of patients, and additional coil embolisation was performed in some 53.8%. SAPT with one of several different acetylsalicylic acid regimens was used in 86% of patients, while antiplatelet protocols were variable overall.

The pooled risks of thromboembolic (23.9%), haemorrhagic (9.4%) and overall (28.3%) complications were calculated “in the absence of publication bias, with low-to-moderate study heterogeneity measures”, Gawlitza et al report. All complications occurred in patients under SAPT with acetylsalicylic acid (ASA)—more commonly referred to as aspirin.

Adequate aneurysm occlusion was described in 65.5% of patients in the study, the authors also state, adding that moderate heterogeneity was observed in few retrospective observational studies, encompassing “a limited number of patients” treated with variable SAPT regimens.

“Flow diversion for ruptured aneurysms under SAPT using stents with hydrophilic polymer and phosphorylcholine coating is feasible, and is associated with low rates of haemorrhagic complications,” Gawlitza et al conclude. “However, thromboembolic complications are frequent and may limit the use of this technique to selected cases. The literature is scarce, with few heterogeneous studies encompassing a limited number of patients treated with highly variable SAPT regimens. However, although more and better data are necessary to conclude on the appropriate medication, it should be noted that all reported thromboembolic complications occurred under SAPT with ASA, which therefore should be used with caution as [the] primary SAPT agent.”