Thrombus magnetic susceptibility: implications for distal embolisation risk in endovascular therapy

BACKGROUND: Distal embolisation (DE) is a common complication following endovascular treatment (EVT) for acute ischaemic stroke. Thrombus magnetic susceptibility may offer predictive insights into DE risk. In this study, we employed quantitative susceptibility mapping (QSM) to measure thrombus susceptibility in patients undergoing EVT and examined its association with DE occurrence. METHODS: Patients with confirmed intracranial large vessel occlusion were consecutively enrolled from a participating centre in the RESCUE-RE study (a registration study for Critical Care of Acute Ischaemic Stroke After Recanalisation). Thrombus magnetic susceptibility was quantitatively measured using three-dimensional multiecho QSM imaging. DE was defined as the appearance of new downstream occlusions on postinterventional digital subtraction angiography. The association between thrombus susceptibility metrics and the occurrence of DE was analysed using multivariable logistic regression, adjusting for relevant clinical and procedural variables. RESULTS: Among the 61 patients included, DE occurred in 29.5% of patients. Thrombi from patients with DE showed significantly higher mean susceptibility values (0.28±0.11 parts per million (ppm) vs 0.22±0.08 ppm, p=0.029). Multivariable analysis identified increased thrombus susceptibility as an independent predictor of DE, with an OR of 2.38 per 0.1 ppm (95% CI 1.04 to 5.45, p=0.039), after adjusting for potential confounders such as National Institutes of Health Stroke Scale score, stroke aetiology, occlusion site, intravenous thrombolysis and time from onset to groin puncture. CONCLUSION: This study identifies thrombus magnetic susceptibility, as quantified by QSM, as a novel imaging biomarker predictive of DE during EVT. These findings highlight the potential of QSM to guide treatment decisions and stratify DE risk preoperatively, although validation in larger cohorts is warranted.