Background and purpose As previously demonstrated, the recanalization rate and clinical outcome in patients with anterior circulation stroke treated with IV thrombolysis (IVT) depend on clot characteristics such as thrombus length and thrombus density. In patients with basilar artery occlusion (BAO) treated with IVT, the recanalization rate has also been shown to depend on thrombus length, although no cut-off value beyond which recanalization would seem impossible has been determined. We aim to evaluate the correlation of clot characteristics with recanalization rate and outcome in patients with BAO treated with endovascular therapy (EVT).

Methods We retrospectively assessed 51 consecutive patients with BAO treated with EVT. Thrombus length and thrombus density (in Hounsfield units, HU) were measured on thin slice non-enhanced cranial CT scan before treatment. Thrombolysis In Myocardial Infarction grade 2–3 was considered successful recanalization and 3-month modified Rankin Scale score 0–2 was considered a favorable outcome. To evaluate the correlation of clot characteristics with recanalization rate and outcome, a binary logistic regression test was computed.

Results Neither thrombus length nor thrombus density correlated with recanalization rate (OR 1.02, 95% CI 0.94 to 1.11, p=0.58 and OR 1.09, 95% CI 0.97 to 1.23, p=0.13, respectively). Thrombus density and thrombus length were not significantly different in patients with (n=41, 80.4%) or without (n=10, 19.6%) successful recanalization (52.3 HU vs 48.4 HU, p=0.07 and 8.2 mm vs 7.5 mm, p=0.91). However, higher clot density was correlated with a favorable outcome (OR 1.31, 95% CI 1.08 to 1.59, p=0.006) whereas thrombus length was not correlated with clinical outcome (OR 0.94, 95% CI 0.86 to 1.03, p=0.20).

Conclusions Successful recanalization does not depend on thrombus length in patients with BAO treated with EVT. Recanalization can therefore be achieved despite high clot burden. Additionally, a high density of thrombi was a strong predictor of a favorable outcome.