Abstract
Introduction: Mechanical thrombectomy with stent retrievers has been demonstrated to improve outcomes in patients with large vessel occlusion. M2 MCA occlusions pose a challenge when M2 branch takeoff has an acute angulation. Acute angles reduce the efficacy of interaction of the device with the clot as the force may be diminished in the vector of the clot. We sought to determine if the Tiger device is affected by an acute angle at the M1-2 MCA junction.
Methods: The Tiger retriever trial was a prospective single-arm multicenter trial to assess efficacy of the Tiger-21 and Tiger-17 devices. A total of 160 patients were enrolled, including 37 with a M2 MCA occlusion. The core lab independently measured the angle on AP projection of the M1-M2 junction blinded to the clinical and radiographic outcomes. Patients were compared for successful reperfusion and if a hemorrhage occurred to assess if angulation was associated with these outcome measures.
Results: A total of 37 patients suffered a M2 MCA occlusion with a mean age 67±16 years and a median NIHSS of 14. The overall rate of first pass TICI 2C/3 was 15/37(40.5%) with 11/37(29.7%) suffering an asymptomatic hemorrhage and no patients noted to have a symptomatic hemorrhage. The final reperfusion of TICI 2b/3 was achieved in 32/37(86.5%) of patients. Patients with excellent M2 TICI 2C/3 reperfusion had a more obtuse angle (113±25 degrees. vs. 92±35 degrees, p<0.03). Patients who suffered an asymptomatic intracranial hemorrhage had a trend towards more acute angulation of the M1-M2 MCA (89±34 degrees vs. 108±31 degrees, p< 0.11). Three patients had an angle <45 degrees all of which suffered asymptomatic subarachnoid hemorrhages. Patients who had an angle <90 degrees also were noted to require more passes to achieve reperfusion compared to patients with angles >90 degrees (3±2.6 vs. 1.8±1.1, p< 0.04).
Conclusions: In the TIGER study, an acute angle at M1-M2 MCA branch point was associated with a reduced rate and need for more passes to achieve successful reperfusion. The acuity of the angle makes catheterization difficult with the force vector diminished along the axis of the clot. The current study identifies an opportunity for technological advancements to overcome this anatomical challenge in M2 MCA thrombectomy.