Letter: Commentary: The Pennsylvania Postmarket Multicenter Experience With Flow Redirection Endoluminal Device.

Abstract

To the Editor: We read with great interest the commentary by Restrepo et al1 discussing our Pennsylvania multicenter postmarket experience with the Flow Redirection Endoluminal Device (FRED) (MicroVention Inc).2 We thank the authors for their interest and the editor for the opportunity to respond. We agree with the authors regarding the multiple important points raised in their commentary. As stated, endoluminal flow diversion (FD) has revolutionized the treatment paradigm of intracranial aneurysms, eventually becoming the standard-of-care treatment for a wide range of lesions, starting from internal carotid artery aneurysms with continuous expansion of its “on-label” utility to multiple “off-label” indications including more distally located and nonsaccular morphologically complex aneurysms.3,4 Despite the initial paradigm-shifting results, improvement of the devices' safety, mostly in decreasing thromboembolic complications, which are the most feared complications of these devices continued to be underway.5,6 These refinements encompassed incessant technical modifications such as introducing new endoluminal devices, establishing intrasaccular flow divertors with the Woven EndoBridge (MicroVention Inc) being the prodigy of these devices,7,8 and surface modifications feature of the existing devices such as Pipeline Embolization Device (PED) (Medtronic) Shield and the FRED-X devices. While large multicenter experiences are currently lacking from the United States, it is worth noting that thromboembolic rates reported from 3 international multicenter studies using the PED Shield (6.4%,9 3.3%,10 2.5%11) were not different from earlier studies using prior PED versions (eg, Prospective Study on Embolization of Intracranial Aneurysms with the Pipeline Device 2.1%12 and IntrePED 3.3%13). Concurrently to the PED Shield, the FRED-X device features a similar nanopolymer surface modification aiming to reduce device thrombogenicity. However, clinical data remain pending to be seen whether there are significant differences in occlusion rates or device's safety profile compared with its predecessor. Multiple questions currently remain in the FD literature; these include the long-term efficacy of the different devices and whether there are any safety/efficacy differences between these devices. A recent systematic review reported a pooled 5-year complete occlusion rate of 96% with most of the literature studies using PED14; however, the analysis did not account for the different FD devices nor particular aneurysmal location, and further studies on this remain warranted. Moreover, limited data are currently known regarding which aneurysm type might be suited for each of those devices and head-to-head comparative performance data of the different devices in certain aneurysms location, for which prospective trials would be needed. Until then, it is likely that operators' technical preferences and personal experiences will continue to be the main impetus for device selection in aneurysms treatment. A recently published survey directed to the US neurointerventional community aimed to elicit common themes in their adoption of the newly introduced devices (ie, Surpass Evolve [Stryker Neurovascular] and FRED devices) to the US market. In this survey, PED was reported as the most common choice for giant aneurysms and ruptured cases (PED Shield in particular), whereas FRED Jr was commonly chosen for distal aneurysms with small parent vessel diameters and Surpass, the device of choice for aneurysms with large parent vessels.15 It has been argued before that the decrease in complications likely stemmed from the device's adequately implied learning curve over time as well as attention to dual antiplatelet therapy and platelet function testing,16 particularly in light of recent level I randomized evidence supporting regular platelet function testing and subsequent medications adjusting in clopidogrel nonresponders or hyporesponders.6 Nonetheless and concurrently to the continuous expansion of the neurointerventional armamentarium with new devices and technologies, a more nuanced approach will likely be needed to identify the most appropriate device with a patient-centered case-specific–based approach.