Clinical and radiographic outcomes after mechanical thrombectomy in medium-vessel posterior cerebral artery occlusions: Subgroup analysis from STAR.

Background: Whereas mechanical thrombectomy (MT) has become standard-of-care treatment for patients with salvageable brain tissue after acute stroke caused by large-vessel occlusions, the results of MT in patients with medium-vessel occlusions (MEVOs), particularly in the posterior cerebral artery (PCA), are not well known.

Methods: Using data from the international Stroke Thrombectomy and Aneurysm Registry (STAR), we assessed presenting characteristics and clinical outcomes for patients who underwent MT for primary occlusions in the P2 PCA segment. As a subanalysis, we compared the PCA MeVO outcomes with STAR's anterior circulation MeVO outcomes, namely middle cerebral artery (MCA) M2 and M3 segments.

Results: Of the 9812 patients in STAR, 43 underwent MT for isolated PCA MeVOs. The patients' median age was 69 years (interquartile range 61-79), and 48.8% were female. The median NIH Stroke Scale score was 9 (range 6-17). After recanalization, 67.4% of patients achieved successful recanalization (modified treatment in cerebral infarction score [mTICI] ≥ 2b), with a first-pass success rate of 44.2%, and 39.6% achieved a modified Rankin score of 0-2 at 90 days. Nine patients (20.9%) had died by the 90-day follow-up. In comparison with M2 and M3 MeVOs, there were no differences in presenting characteristics among the three groups. Patients with PCA MeVOs were less likely to undergo intra-arterial thrombolysis (4.7% PCA vs. 10.1% M2 vs. 16.2% M3, p = 0.046) or to achieve successful recanalization (mTICI ≥ 2b, 67.4%, 86.7%, 82.3%, respectively, p < 0.001); however, there were no differences in the rates of successful first-pass recanalization (44.2%, 49.8%, 52.3%, respectively, p = 0.65).

Conclusions: We describe the STAR experience performing MT in patients with PCA MeVOs. Our analysis supports that successful first-pass recanalization can be achieved in PCA MEVOs at a rate similar to that in MCA MeVOs, although further study and possible innovation may be necessary to improve successful PCA MeVO recanalization rates.