Background Few case reports have considered the chromatic aspect of retrieved clots and the possible association with their underlying etiology.

Objective The aim of our study was to analyze the frequency of the TOAST ischemic stroke typical (atrial fibrillation, dissection, atheroma) and atypical (infective endocarditis, cancer-related, valve-related thrombi) etiologies depending on the chromatic aspect of retrieved clots.

Methods A total of 255 anonymized and standardized clot photos of consecutive patients treated by mechanical thrombectomy for acute ischemic stroke were included. A double-blind evaluation was performed by two senior interventional neuroradiologists, who classified the visual aspects of the clots into two main patterns: red/black or white. Main patient characteristics, distribution of underlying stroke etiologies, and outcomes were compared between the two study groups.

Results The inter-reader agreement for clot colors was excellent (k=0.78). Two hundred and thirty-three patients were classified as having red/black clots and 22 as having white clots. A statistically significant association (p=0.001) between atypical etiologies and white clots was observed.

Conclusions White clots were significantly associated with atypical etiologies in this cohort,in particular, with infectious endocarditis.