The Source for Neurovascular News and Education

September 26, 2021


The findings add to increasing evidence that flow diversion is appropriate even for small aneurysms in distal locations.


The Flow Re-Direction Endoluminal Device (FRED; MicroVention) can be used to treat aneurysms in the internal carotid artery (ICA) as well as at more distal sites safely and effectively, according to results of the single-arm SAFE trial published online January 19, 2018, ahead of print in the Journal of NeuroInterventional Surgery.

“Flow diversion has dramatically changed the management of large and giant aneurysms and is now also playing an important role in the treatment of medium and small aneurysms, [particularly] those with a wide neck,” lead author Laurent Pierot, MD (Hôpital Maison-Blanche, Reims, France), told Neurovascular Exchange in an email. “FRED is a new-generation flow diverter that features a specific double-layer design, where the inner layer acts as a flow diverter while the outer layer ensures optimal opening and wall apposition.”

The FRED device is increasing in popularity where it is approved for use, which is mainly in Europe; it has not been approved for use in the United States. “It is relatively easy to place and deploy through a Headway 27 microcatheter (or Headway 21 microcatheter for the FRED Jr.), [even] in patients with very tortuous, atherosclerotic vessels, which is not the case for all flow diverters,” noted Pierot.

For the SAFE trial, Pierot and colleagues prospectively followed 103 patients treated for an intracranial aneurysm using the FRED or FRED Jr. device at one of 13 interventional neuroradiology centers. Aneurysms were located in the supraclinoid ICA (68.9%), cavernous ICA (14.6%), anterior cerebral artery or anterior communicating artery (8.7%), or middle cerebral artery (7.8%). Aneurysms were small (< 10 mm) in 68.9% of cases.

Treatment was successfully performed in 98 of 103 patients (95.1%). Six-month outcome data revealed low rates of mortality (1.0%) and morbidity (2.0%).

Adverse events were independently evaluated by a Clinical Event Committee that included a vascular neurosurgeon and an interventional neuroradiologist. The primary adverse events were thromboembolic complications in 4.9%, intraoperative rupture in 1.9%, delayed aneurysm rupture in 1.0%, and delayed hematoma in 1.0%.

“Compared to previous-generation devices, FRED is associated with a lower [morbidity and] mortality,” said Pierot. “One major limitation in the use of flow diverter is that, with the first-generation devices, the safety was a little bit worse compared to other endovascular approaches. SAFE shows that, by changing the design of the device, it is possible to reduce complication and morbi-mortality rates.” He pointed out, however, that outcomes are improving overall with flow diversion simply because interventionalists are becoming more experienced with the devices.

Use of the FRED is not difficult to master, Pierot added. As with other flow diverters, it is important to select the correct diameter, length, and placement. “When selecting the length of the FRED device, it is important to take in consideration the fact that, at the proximal and distal ends, 3 mm of the device [is] just stent and not flow-diverting,” he noted. “It is also important to properly place the flow-diverting portion of the device in front of the aneurysm neck.”

The SAFE trial has shown that FRED can be used safely for aneurysms located not only in the ICA but also in more distal sites, such as the middle cerebral artery and anterior cerebral artery, said Pierot. The risks and benefits of flow diversion for bifurcation aneurysms still remain uncertain, however.

Limitations of the study, he noted, are a lack of control group undergoing aneurysm repair using another form of endovascular intervention and lack of long-term follow-up. The patients in this study are being followed out to 1 year, and the results will be published when available.



Pierot L, Spelle L, Berge J, et al. Feasibility, complications, morbidity, and mortality results at 6 months for aneurysm treatment with the Flow Re-Direction Endoluminal Device: report of SAFE study. J NeuroIntervent Surg. 2018;Epub ahead of print.



  • The SAFE study was funded by MicroVention.
  • Pierot reports being a consultant to MicroVention.