Higher Annual Operator Volume Is Associated With Better Reperfusion Rates in Stroke Patients Treated by Mechanical Thrombectomy: The ETIS Registry

Abstract

Objectives: The aim of this study was to determine whether individual operator characteristics have an impact on reperfusion and procedural complication rates.

Background: Mechanical thrombectomy (MT) is a Level IA treatment in acute ischemic stroke (AIS) patients. The operator's effect has been found to be an independent predictor for clinical outcome and technical performance in interventional cardiology.

Methods: From the ETIS (Endovascular Treatment in Ischemic Stroke) study, a prospective, multicenter, observational real-world MT registry, the authors included all AIS patients consecutively treated by MT between January 2012 and March 2017 in 3 high-volume comprehensive stroke centers by 19 operators. We assessed the effect of individual operator characteristics on successful reperfusion, defined as modified Thrombolysis In Cerebral Infarction 2b/3 at the end of MT, and procedural complications using multivariable hierarchical logistic regression models.

Results: A total of 1,541 patients with anterior and posterior AIS were enrolled (mean age 67 years; median NIHSS 16). There was a significant operator effect on successful reperfusion, with an intraclass correlation coefficient of 0.036 (p = 0.046), but not on complications (intraclass correlation coefficient = 0). There was a dose-response relationship between annual operator volume and successful reperfusion rate (p = 0.003) with an adjusted odds ratio for successful reperfusion equal to 2.52 (95% confidence interval: 1.37 to 4.64) for patients treated by an operator with an annual volume ≥40 MT/year compared with those treated by an operator with <14 MT/year (first tertile). Nevertheless, this result did not translate to better clinical outcomes.

Conclusions: Our data suggest that operator volume of MT/year has a positive impact on successful reperfusion in AIS patients, but not on clinical outcomes nor on complication rates. Further studies are warranted to investigate threshold procedure numbers associated with better outcomes.

Keywords: ETIS register; acute ischemic stroke; mechanical thrombectomy; operator volume.