Response to Letter Regarding Article, “Optimizating Clot Retrieval in Acute Stroke: The Push and Fluff Technique for Closed-Cell Stentrievers”
We appreciate the interest in our study. The technique of applying forward force on the delivery wire and microcatheter during stent deployment actually derived from the process of optimizing device wall-apposition as well as generating shouldering, which have been previously used in the treatment of wide-necked aneurysms with Enterprise and Neuroform stents (pre-pipeline era). Indeed, the response of braided, open-cell, and closed-cell to delivery techniques is notoriously different. However, varied within-class stent engineering designs may lead to substantially different behaviors. In vitro testing of the push and fluff technique for the Trevo Retriever (M. Gounis, unpublished data) has corroborated a substantially enhanced clot integration compared with standard unsheathing technique. We think that the Trevo device allows diameter expansion because of its particular cell geometry, cell size, undulated sidewall, and vertical strut design. These characteristics allow the device to move forward and expand symmetrically without significant ovalization.
It is important to highlight that despite the a priori concern regarding the potential of having increased wall tension/abrasion on vessel wall/endothelium with the push and fluff technique, the safety profile of our push and fluff technique arm versus Thrombectomy Revascularization of Large Vessel Occlusions in Acute Ischemic Stroke (TREVO2) trial Trevo arm was nearly statistically superior to unsheathing technique regarding rates of parenchymal hemorrhage and subarachnoid hemorrhage (11% versus 23%; P=0.08 and 4% versus 12%; P=0.09, respectively). Even when we compare our institutional experience (using the European Cooperative Acute Stroke Study [ECASS] definition of parenchymal hematoma, which is more sensitive than the Safe Implementation of Thrombolysis in Stroke-Monitoring Study [SITS-MOST] definition of symptomatic hemorrhage), there was not even a signal of a potential interaction between the push and fluff technique with hemorrhagic complications (parenchymal hemorrhage and subarachnoid rate of 11% versus 10%; P=0.79 and 4 versus 6%; P=0.60, respectively). The TREVO2, Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment (SWIFT PRIME), Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion with Emphasis on Minimizing CT to Recanalization Times (ESCAPE), Randomized Trial of Revascularization With Solitaire FR Device Versus Best Medical Therapy in the Treatment of Acute Stroke Due to Anterior Circulation Large Vessel Occlusion Presenting Within Eight Hours of Symptom Onset (REVASCAT), Extending the Time for Thrombolysis in Emergency Neurological Deficits — Intra-Arterial (EXTEND-IA), and Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN) trials had a difference between treatment groups for parenchymal hemorrhage ranging from 0% to 3% (median 0.9%). Considering that these trials evaluated 2 completely different treatment modalities (either intervention versus medical therapy or 2 different devices) and lead to a minimal difference in parenchymal hemorrhage rates, it is difficult to expect that a simple difference in delivery used in the same device would lead to a parenchymal hemorrhage rate >8% (which become clearly an excessive and arbitrary threshold). Moreover, according to the proposed analysis by See et al,1 all the aforementioned trials (with exception of MR CLEAN) would not have sufficient power to demonstrate safety of the most powerful stroke treatment modality ever described. Finally, if we perform a study with similar alpha and power and with >40 000 patients, we could prove that the 1% difference in parenchymal hemorrhage is statistically different. However, increasing sample size may simply and invariably lead to stronger statistical power to detect statistical/mathematical but not necessarily contextually important biological differences.
Diogo C. Haussen, MD
Leticia C. Rebello, MD
Raul G. Nogueira, MD
Emory University School of Medicine/Marcus Stroke & Neuroscience Center
Grady Memorial Hospital
Sources of Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Dr Nogueira has the following disclosures: Stryker Neurovacular (Trevo-2 Trial PI, DAWN Trial PI), Covidien (SWIFT and SWIFT-PRIME Steering Committee, STAR Trial Core Laboratory), and Penumbra (3-D Separator Trial Executive Committee). Drs Haussen and Rebello report no conflicts.
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