Background and Purpose
Thin-section non-contrast CT (NCCT) images can be used to measure hyperdense clot length in acute ischemic stroke (AIS). Clots ≥8mm have a very low probability of IV-tPA recanalization, and hence may benefit from a bridging intra-arterial approach. To understand the prevalence of such clots, we sought to determine the distribution and predictors of clot lengths in consecutive anterior circulation proximal artery occlusions.
Of 623 consecutive AIS patients, fifty-three met inclusion criteria: presentation <8 hours from onset; intracranial ICA-terminus or proximal-MCA occlusion; admission thin-slice NCCT (≤2.5mm); and no IV-tPA pre-treatment. For each patient, hyperdense clot length was measured and recorded along with additional relevant imaging and clinical data.
Mean age was 70 years, and mean time-to-CT was 213 minutes. Median baseline NIHSS was 16.5. Occlusions were located in the ICA-terminus (34% [18/53]), MCA M1 (49%[26/53]) and M2 segments (17% [9 of 53]). Hyperdense thrombus was visible in 96%, with mean and median clot lengths (mm) of 18.5 (±14.2) and 16.1 (7.6-25.2), respectively. Occlusion location was the strongest predictor of clot length (multivariate p=0.02). Clot length was ≥8mm in 94%, 73%, and 22% of ICA-terminus, M1, and M2 occlusions, respectively.
The majority of anterior circulation proximal occlusions are ≥8mm long, helping to explain the low published rates of IV-tPA recanalization. ICA-terminus occlusion is an excellent marker for clot length ≥8mm; vessel-imaging status alone may be sufficient. Thin-section NCCT appears useful for patients with MCA occlusion due to the wide variability of clot lengths.