Learning Curve for Flow Diversion of Posterior Circulation Aneurysms: A Long-Term International Multicenter Cohort Study

BACKGROUND AND PURPOSE

Flow diversion has gradually become a standard treatment for intracranial aneurysms of the anterior circulation. Recently, the off-label use of the flow diverters to treat posterior circulation aneurysms has also increased despite initial concerns of rupture and the suboptimal results. This study aimed to explore the change in complication rates and treatment outcomes across time for posterior circulation aneurysms treated using flow diversion and to further evaluate the mechanisms and variables that could potentially explain the change and outcomes.

MATERIALS AND METHODS

A retrospective review using a standardized data set at multiple international academic institutions was performed to identify patients with ruptured and unruptured posterior circulation aneurysms treated with flow diversion during a decade spanning January 2011 to January 2020. This period was then categorized into 4 intervals.

RESULTS

A total of 378 procedures were performed during the study period. Across time, there was an increasing tendency to treat more vertebral artery and fewer large vertebrobasilar aneurysms (P = .05). Moreover, interventionalists have been increasingly using fewer overlapping flow diverters per aneurysm (P = .07). There was a trend toward a decrease in the rate of thromboembolic complications from 15.8% in 2011-13 to 8.9% in 2018-19 (P = .34).

CONCLUSIONS

This multicenter experience revealed a trend toward treating fewer basilar aneurysms, smaller aneurysms, and increased usage of a single flow diverter, leading to a decrease in the rate of thromboembolic and hemorrhagic complications.

Abstract TP19: Thrombectomy in Medium Arteries Works for Distal Vessel Occlusions in Acute Ischemic Stroke - STRATIS

Background: Mechanical thrombectomy is established for large vessel occlusions in acute ischemic stroke, but the potential role in distal vessel occlusions of medium arteries is largely unknown. Such distal arterial segments have not been measured with respect to thrombectomy devices used during endovascular therapy. We conducted a systematic analysis of arterial size, segmental anatomy and stent retriever device performance during thrombectomy.

Methods: The STRATIS angiography core lab adjudicated the exact location of the occlusion, proximal and distal device deployment, relationship to arterial bifurcations and anatomical nomenclature. Arterial diameters were measured at all of these sites. Statistical analyses examined the relationship between these variables, arterial recanalization and eTICI reperfusion.

Results: Thrombectomy was performed with various device sizes, including Solitaire 4x40 in 36.3% (306/844), Solitaire 6x30 in 31.4% (265/844), Solitaire 4x20 in 26.4% (223/844), unspecified in 3.8% (32/844), Solitaire 6x20 in 1.3% (11/844) and Solitaire 4x15 in 0.8% (7/844). Arterial diameter at the occlusion site was median 2.17mm (1.40-3.59) in the distal M1, 1.67mm (0.81-2.98) in the proximal M2, 1.50mm (0.92-1.99) in the distal M2, 1.24mm (0.67-2.00) in the M3 and 1.88mm (1.49-1.94) in the P1. Considerable overlap was noted between arterial sizes at occlusion sites carrying different segmental arterial nomenclature or vessel names. During device deployment in STRATIS, median arterial diameter at the occlusion site was 2.4mm (IQR 1.9, 3.4), 2.9mm (IQR 2.2, 3.6) at the proximal stent marker and 1.4mm (IQR 1.2, 1.7) at the distal stent marker. Substantial eTICI reperfusion (2b-3) was achieved in all distal vessel occlusions (Table 1).

Conclusions: Substantial reperfusion may be achieved with currently available mechanical thrombectomy devices for distal vessel occlusions in medium arteries.

Abstract WP24: Arterial Tortuosity is a Potent Determinant of Safety in Endovascular Therapy for Ischemic Stroke

Background: Subarachnoid hemorrhage (SAH) associated with vessel injury during endovascular therapy for acute ischemic stroke is a known complication. Arterial anatomy may predispose to increased risk of SAH and technical safety, yet factors such as clot location, arterial size and tortuosity have not been explored. We examined these anatomical factors with respect to SAH during thrombectomy.

Methods: Arterial anatomy at the site of occlusion and mechanical thrombectomy during device deployment was detailed by the STRATIS core lab. Luminal diameters, arterial branching and segmental tortuosity were measured. Arterial tortuosity was quantified using the distance factor metric (DFM). Statistical analyses included descriptives of arterial anatomy, with univariate and multivariate modeling to predict SAH.

Results: Arterial tortuosity in each segment from the proximal cerebral arteries to the site of occlusion was quantified in 790 subjects treated with mechanical thrombectomy in STRATIS. Cumulative arterial tortuosity to the site of vessel occlusion was greater in distal lesions (Table 1). SAH was clearly linked with more distal thrombectomy (p=0.017), with 19.0% of distal M2, 16.7% of M3, 7.3% of distal M1, 5.8% of proximal M2, 2.4% of distal ICA and 2.1% of proximal M1. Multivariate prediction of SAH revealed that arterial diameter was unrelated to SAH (p=0.30) when accounting for tortuosity, whereas the presence of tortuosity tripled the risk of SAH (OR 3, p<0.05).

Conclusions: This novel systematic analysis of arterial tortuosity and angiographic anatomy during mechanical thrombectomy establishes tortuosity as a determinant of SAH, providing insight for future techniques and innovative device designs.

Abstract TMP4: Serial ASPECTS from Baseline to 24 Hours: Impact of Endovascular Therapy in STRATIS

Background: Serial ASPECTS of ischemic stroke lesion evolution from baseline to 24-hours has been established as an effective surrogate endpoint in endovascular therapy. The use of this imaging shift has not been implemented beyond thrombectomy trials to estimate impact of endovascular therapy in large-scale registry data.

Methods: The STRATIS Imaging Core Lab, blind to all clinical data, independently determined ASPECTS scores on baseline and 24-hour studies. ASPECTS regional involvement and resulting total scores were analyzed in anterior circulation occlusions in STRATIS. Statistical analyses calculated the proportion of subjects with 0 ASPECTS score shift and separately, those with shifts >4, 5, 6 points. Clinical predictors of ASPECTS shift and regional involvement were determined.

Results: Baseline ASPECTS (n=517) was 8.2 ± 1.59 (median 8.0 (2, 10)) and 24-hour ASPECTS (n=547) was 6.0 ± 2.92 (median 7.0 (0, 10)). Serial ASPECTS (n=487) revealed change of -2.1 ± 2.41 (median-1.0 (-10, 3)). Absolutely no change in ASPECTS, or 0 shift from baseline to 24 hours, occurred in 157/487 (32%). Substantial ASPECTS decline of ≥4 occurred in 117/487 (24%), with ≥5 in 76/487 (16%) and ≥6 in 51/487 (10%). ASPECTS decline was linked with baseline collaterals (ASITN 4 (n=19; -0.9 ± 1.05); 3 (n=117; -0.8 ± 1.21); 2 (n=140; -2.6 ± 2.27); 1 (n=29; -3.6 ± 2.34); 0 (n=10; -4.2 ± 3.08)) and the degree of subsequent reperfusion (oTICI 3 (n=63; -1.1 ± 1.94); 2B (n=282; -1.9 ± 2.32); 2A (n=103; -3.4 ± 2.38); 1 (n=2; -3.0 ± 1.41); 0 (n=10; -4.0 ± 2.75)). Baseline predictors of ≥6 ASPECTS decline included previous TIA (OR 3.10 (95%CI 1.32, 7.31), diabetes (OR 2.23 (95%CI 1.22, 4.07)) and baseline NIHSS (OR 1.10 (95%CI 1.03, 1.16).

Conclusions: Frozen ASPECTS or 0 shift from baseline to 24 hours occurs in about 1/3 of all cases treated with endovascular therapy in a large-scale registry. Poor collaterals, prior TIA, diabetes and elevated baseline NIHSS may be important predictors of those likely to experience infarct evolution despite reperfusion, identifying optimal candidates for neuroprotection with endovascular therapy.

Abstract TP36: Collaterals Negate Time: Topography and Determinants of Baseline ASPECTS in STRATIS

Background: ASPECTS is routinely used to estimate ischemic lesion burden in acute stroke, yet the topography and influence of collaterals has been unexplored. Imaging selection for endovascular therapy in various time epochs may also be simplified with ASPECTS. We leveraged the large-scale registry data of STRATIS to discern the role of collaterals, time and other factors in ASPECTS topography at baseline.

Methods: The STRATIS Imaging Core Lab, blind to all clinical data, independently determined ASPECTS scores and regional involvement in anterior circulation occlusions. Collateral status on baseline angiography was scored by ASITN grade. Statistical analyses described ASPECTS regional involvement or topography based on arterial occlusion site and other variables available prior to intervention, determining the influence of collaterals and time duration from onset to imaging.

Results: Baseline ASPECTS (n=573) was median 8.0 (2, 10). ASPECTS regions involved were lenticular nuclei 62.3% (357/573), insula 42.2% (242/573), caudate 23.4% (134/573), M2 13.6% (78/573), M4 9.4% (54/573), M5 9.2% (53/573), M1 4.0% (23/573), M3 2.1% (12/573), M6 1.9% (11/573) and internal capsule 0.2% (1/573). Distinct patterns or topography differentiated ICA, M1 and M2 arterial occlusion sites at angiography. Overall, higher ASPECTS (7-10 vs. ≤ 6) was linked with more robust collaterals (p<0.001) and shorter duration from onset to CT (p=0.001), yet collateral grade was unrelated to time. Ordinal multivariate logistic regression on ASPECTS containing collateral grade and time (from onset to CT) as covariates demonstrated that they were significantly associated (p<0.001 and p=0.0024, respectively) with ASPECTS.

Conclusions: ASPECTS topography and the extent of ischemic changes are a product of arterial occlusion site, collateral status and time duration. ASPECTS may infer collateral status, a pivotal determinant of outcome in endovascular therapy, irrespective of time from symptom onset.

Cerebral infarction secondary to vasospasm after perimesencephalic subarachnoid hemorrhage

Perimesencephalic subarachnoid hemorrhage (pSAH) has been described as a distinct form of subarachnoid hemorrhage (SAH) associated with good outcomes. We report a 48-year-old female who developed cerebral infarction due to severe diffuse vasospasm following pSAH. The patient presented with non-aneurysmal pSAH and was discharged home on day 5. However, one week later she developed an acute onset of right hemiparesis. A brain MRI showed acute infarctions on diffusion weighted imaging and her cerebral angiogram showed diffuse vasospasm. The patient received intra-arterial diltiazem and hypervolemic-hypertensive-hemodilution therapy with resulting resolution of the vasospasm and hemiparesis. While not as common as in SAH, there is a potential for the occurrence of cerebral infarction due to vasospasm after pSAH.