This study included 39 patients (18 male, 21 female) with a mean age of 69.9 (± 13.3, range 26–88) years who received a mechanical thrombectomy with NeVaTM stent retriever, selected from a total cohort of 212 patients receiving mechanical thrombectomy within the study period. A total of 25 (64.1%) patients presented with vascular occlusion of the M1 segment of the middle cerebral artery (MCA-M1), 7 (17.9%) patients with occlusion of the M2 segment of the middle cerebral artery (MCA-M2), 3 (7.7%) patients presented with a combined occlusion of the internal carotid artery (ICA) and an intracranial vessel (2× M1, 1× M2), and 4 (10.3%) patients presented with occlusion of the basilar artery (BA). Vessel occlusions of anterior circulation were located on the right side in 22 (56.4%) and on the left side in 13 (33.3%) of patients. Systemic lysis therapy was performed in 15 (38.5%) patients. The mean time from onset of symptoms to femoral puncture was 297.8 ± 203.6 min. Etiology of stroke was cardioembolic in 12 (30.8%) patients, thrombotic due to local stenosis in 2 (5.1%) patients, due to aortic valve endocarditis in 1 (2.6%) patient, embolic after thoracic surgery in 1 (2.6%) patient, due to drug abuse in 1 (2.6%) patient, and unknown in 22 (56.4%) patients.

Detailed patient characteristics are shown in Table 1.

Detailed information on procedural characteristics and technical outcome are shown in Table 2 and recanalization rates are also illustrated in Fig. 3. The NeVaTM stent retriever was used as first-line thrombectomy device in 24 (61.5%) patients and in 15 (38.5%) patients as second-line device. A balloon-guided catheter was used in 30 (76.9%) patients; an intermediate catheter was used in 13 (33.3%) patients. Additional stenting was performed in 4 (10.3%) patients due to underlying stenosis (75%) or dissection (25%, not NeVaTM stent retriever related).

mTICI scores of first- or second-line NeVaTM stent retriever use. mTICI scores 1) after NeVaTM stent retriever as first-line device 2), after NeVaTM stent retriever as first-line device + additional maneuvers (ADM; other devices, rescue etc.) 3), before NeVaTM stent retriever as second-line device 4), after NeVaTM stent retriever as second-line device, and 5) final mTICI score of the entire cohort

When NeVaTM stent retriever was used as first-line device (24/39 patients), a mean of 1.2±0.4 passes was performed. Here, a first-pass rate mTICI ≥ 2c of 66.7% (16/24 patients) was observed. After first-line use of NeVaTM stent retriever, a rate of mTICI≥ 2b of 91.7% (22/24) and of mTICI≥2c of 18/24 (75%) was achieved. Successful recanalization ≥ mTICI 2c was achieved in all (16/16, 100%) procedures, where only the NeVaTM stent retriever and no other device has been used.

Additional maneuvers with a different stent retriever to further improve recanalization rate were performed at the discretion of the performing neurointerventionalist in 7/24 (29.1%) patients with a mean of 1.7±0.9 additional passes. Those additional stent retrievers were mainly used for the remaining peripheral vessel occlusions (≥ distal M2) after partial recanalization (4/7, 57.1%), while they were used for remaining main vessel occlusion in 2/7 (28.6%) and in 1/7 (14.2%) for peripheral vessel occlusion (A3) due to embolization to new territory. Final mTICI rate after first-line NeVaTM stent retriever and additional maneuvers was mTICI ≥ 2c of 100% (24/24).

NeVaTM stent retriever was used as second-line device for mechanical thrombectomy in 15/39 (38.5%) patients. A mean number of 2.1±1.7 passes were performed with other stent retrievers afore NeVaTM stent retriever was used. Here, in 6/15 patients a pRESET 6 × 50 mm (phenox, Bochum, Germany) was used before usage of NeVaTM stent retriever, while in 3/15 patients a pRESET 6 × 50 mm and a CatchView 5.5 × 50 mm (balt, Montmorency, France), in 2/15 patients a CatchView 5.5 × 50 mm, in 1/15 patient a pRESET 6 × 50 mm and a pRESET 4 × 20 mm, in 1/15 patient a pRESET 6 × 30 mm, in 1/15 patients a pRESET 6 × 30 and a CatchView 5.5 × 50 mm, and in 1/15 patients a pRESET 4 × 20 mm stent retriever was used. Before usage of NeVaTM stent retriever, the rate of mTICI ≥2b/2c was 6.7% (1/15, second-line NeVaTM stent retriever was used for remaining M2 in this case) with all other patients showing mTICI ≤ 2a (mTICI 0: 9; mTICI 1: 3; mTICI 2a: 2).

A mean of 1.7±1.4 passes with NeVaTM stent retriever as second-line device was performed, showing a first-pass rate mTICI ≥2c of 66.7% (10/15 patients). Herewith, the rate of mTICI ≥2b improved to 86.7 % (13/15) and of mTICI ≥ 2c to 80% (12/15). The two patients still showing mTICI <2b after second-line NeVaTM maneuvers were both also not recanalizable with any other additional maneuvers/devices (final mTICI score 0 and 1, respectively). No embolization to new territory was observed in the second-line group.

Summarizing the entire cohort (39 patients) with first- or second-line use of NeVaTM stent retriever, a total of 2.9±3.0 passes (median 2, range 1–16), of which 1.4±0.9 passes (median 1, range 1-5) were with NeVaTM stent retriever, were performed. NeVaTM stent retriever first-pass rate mTICI ≥2c was 66.7% (26/39). After thrombectomy with NeVaTM stent retriever first- or second-line and additional maneuvers, a rate of mTICI ≥2b of 94.9% (37/39) and of mTICI ≥2c of 92.3% (36/39) was observed.

There were neither any baseline patient characteristics (age, sex, mRS, NIHSS, location, side or number of vessel occlusions, etiology of stroke) nor any procedural parameters (systemic i.v. lysis prior to thrombectomy, use of balloon-guided or intermediate catheter, NeVaTM stent retriever as first- or second-line device) significantly associated with a successful first-pass recanalization of the NeVaTM stent retriever (all p-values >0.05).

No minor or major adverse events were observed in the study cohort. Only 1 patient (2.6%) showed NeVaTM stent retriever-associated intracranial vasospasm after thrombectomy, which fully resolved after short increase in running rate of catheter flushing solution containing nimodipine. A total of 13/39 (33.3%) patients showed a hemorrhage at 24h postprocedural CT scan, of which none was a symptomatic intracerebral hemorrhage (SICH) as defined by worsening of the NIHSS of at least four points. In these cases, vessel occlusion was located in 9/13 (69.2%) within the M1-segment, in 3/13 (23.1%) patients within the M2-segment and in 1/13 (7.7%) within the ICA and M1-segment. We have added this information to the results section of the manuscript. Overall in-hospital mortality rate was 4/39 (10.3%) patients.

NIHSS score showed significant differences at admission, 24h after MT, and at discharge as revealed by the Friedman test (X2=22.4, p<0.001). Here, Friedman post hoc test showed that NIHSS was significantly lower at 24h after MT (13.1±12.1, p=0.008) and at discharge (11.2±12.7, p<0.001) than at admission (13.9±6.8). Meanwhile, NIHSS was not significantly different at 24h after MT compared to discharge (p=0.141). mRS improved significantly from 4.6±0.8 at admission to 3.3±2.0 at discharge (p<0.001). mRS 0–2 was reached in 14/39 (35.9%) of patients at discharge.