Refractory Thrombectomy: Incidence and Related Factors in a Third-Level Stroke Treatment Center

Background/Objectives: The efficacy of mechanical thrombectomy in large vessel occlusion has been established in multiple clinical trials as the standard of care for acute ischemic stroke. However, the incidence of refractory thrombectomy (RT), as well as related factors, remains unclear. Methods: We designed a retrospective study based on our prospective database from December 2014 to December 2023, collecting together the data on patients with large/medium vessel occlusion and reperfusion technique failure. We analyzed clinical, laboratory, histopathological, and radiological markers, as well as predictive variables of RT, mRS at three months, and symptomatic intracranial hemorrhage (sICH). Results: Among 733 patients, the incidence of refractory thrombectomy was 7.4% (n = 54). The most relevant causes were technical difficulties in passing through the occlusion (33.3%), clot resistance to extraction despite correct device placement (31.5%), and underlying intracranial stenosis (13%). A total of 20 recalcitrant thrombi were analyzed. Both atherotrombotic cause (OR 4.22, CI 95% 1.1-16.25; p = 0.04) and the absence of hyperdense artery sign (HAS) on CT (OR 0.26, 95% CI 0.09-0.79; p = 0.02) were independent predictors of RT outcome. For sICH, independent predictors were NIHSS at admission (OR 1.1; 95% CI 1.02-1.18; p = 0.008), protective effect in M1 occlusions (OR 0.28; 95% CI 0.09-0.88; p = 0.03), and prior IV thrombolysis (OR 0.38; 95% CI 0.16-0.93; p = 0.03). Finally, for favorable clinical outcome (mRS 0-2), a correlation was found with the NIHSS score at admission (OR 1.11; 95% CI 1.08-1.14; p = 0.0001), a history of diabetes (OR 0.53, 95% CI 1.02-1.18; p= 0.004), and RT status (OR 0.06, 95% CI 0.01-0.31; p = 0.001). No direct relationship was found between the clot composition and prognostic variables or first-line recanalization strategy. Conclusions: In our cohort, the incidence of refractory thrombectomies was low and associated with a worse clinical outcome. Absence of the hyperdense artery sign and the atherothrombotic stroke subtype were found to be independent predictors of refractory recanalization.