Despite improved endovascular techniques, advances in catheter and stent retriever technology, and accumulated user experience, mechanical thrombectomy fails to achieve successful revascularization in approximately 20% of patients. 

A prospectively maintained database of MT patients between January 2013 and August 2021 was interrogated. Failed MT was defined as final reperfusion score mTICI (modified Thrombolysis in Cerebral Infarction) < 2B. We collected demographic data, procedural details, stroke etiology, and anatomic data in patients who underwent MT with subsequent failed reperfusion. 

Of a total 1010 MT procedures, 120 (11.9%) were unsuccessful. Mean age was 66.8 years, 51.5% were male, and 61.1% were Caucasian. The most common failure location was intracranial (93.3%) followed by failure at the arch (3.33%) and neck (3.3%). Among patients who failed intracranially, underlying intracranial arterial stenosis (ICAS) was the cause of failure in 84 patients (70%). Compared to successful MT, failed MT patients had longer onset to puncture (p=0.012) and groin time (p=0.004). Rescue stenting was more common in the successful MT group (12% vs 5.1%, p=0.024). Multivariate analysis demonstrated that Diabetes Mellitus (p = 0.009), > 3 thrombectomy passes (p <0.001), and longer onset to groin time (p = 0.004) were independently associated with unsuccessful recanalization. 

Failed MT is encountered in approximately 12% of MT procedures. The most common cause of failed MT was underlying ICAS. Further studies to evaluate better ways of early identification and treatment of ICAS related LVO are warranted.