Elena Zapata-Arriaza, MD

Zaidat OO, Haussen DC, Hassan AE, Jadhav AP, Mehta BP, Mokin M, et al. Impact of Stent Retriever Size on Clinical and Angiographic Outcomes in the STRATIS Stroke Thrombectomy Registry. Stroke. 2019;50:441–447.

The introduction of stent retriever has involved a great advance in the reperfusion treatment of acute ischemic stroke with large vessel occlusion. Stent retriever has increased procedural success, leading the American Heart Association/American Stroke Association guidelines to recommend the use of stent retrievers for mechanical thrombectomy within 8 hours of symptom onset. However, some concerns related to the safety and efficacy of the stent retriever are maintained regarding its diameter and size.

To answer the question, Zaidat et al. performed a retrospective ad hoc analysis of data from the STRATIS registry (a prospective, multicenter study of patients with large vessel occlusion treated with the Solitaire stent retriever). Main angiographic end points were first-pass effect (FPE), defined as modified thrombolysis in cerebral infarction (mTICI) ≥2c recanalization grade after the first pass without the use of rescue therapy, and rates of modified FPE (mFPE), defined as meeting all criteria for FPE but achieving mTICI ≥2b after first pass. The primary clinical endpoint was functional independence (modified Rankin scale, 0–2) at 3 months as determined on-site. Rates of distal embolization, embolization into new territory, and final mTICI among others were evaluated as well.

Among 715 included patients, the 4×20 stent retriever was used in 28% patients, 4×40 was used in 38% patients, and the 6×30 was used in 34%patients. The main results (shown in Table 2) can be resumed in the following; employment of 4×40 stent retriever had the highest rate of FPE and modified FPE. Final revascularization was not significantly different across the groups, and there were no significant differences in functional dependence or mortality at 90 days post-procedure. Use of the longer stent retriever (4×40) was an independent predictor of achieving modified FPE. In addition, 4×40 Solitaire use showed the lowest number of device passes, and the rate of embolization into new territory was significantly lower in this group. Finally, regarding revascularization efficacy of stent retriever sizes at different clot locations, this highlights the fact that patients treated with the 4×40 stent retriever had the highest rate of mFPE after first pass in internal carotid artery occlusion instead of the most frequent and larger diameter device (6×30).

Clinical and Angiographic Outcomes by Stent Retriever Diameters and Lengths

Longer is better, but only a half could be final performance of this manuscript, based on the evidence shown in the results. Longer stent retriever showed a higher rate of revascularization when compared with the shorter or larger diameter stent retriever, but was not associated with better clinical outcome. Regarding the results of diameter versus length, there seems to be a clear benefit of the latter. In the occlusions of the internal carotid artery and proximal MCA, the stent of more diameter (6×30) does not provide higher benefit; however, longer stent (4×40) induces better revascularization rates. Of course, generalizing these results without conducting a randomized trial should be done with caution, but the mentioned findings suggest that the benefit in recanalization rates over a diameter is lost in pursuit of greater length.

The main limitations of the study are: not randomization, stent retriever size availability and preference of use, the lack of 6×40 device employment, and the fact that final reperfusion and clinical outcomes could be influenced by adjunctive techniques. Further studies are needed to confirm these interesting findings.