Abstract TP33: Early DWI Changes in the Thrombolysis Time Window: From DWI-Negative to Malignant Stroke in More than 300 Cases
Background: Thrombolysis for acute stroke is routinely based on time from last known well (TLKW) as the extent of ischemic injury during early epochs is assumed to be minimal. DWI is extremely sensitive, yet rarely acquired prior to thrombolysis and the nature of DWI lesions is largely unknown during this time window. Large or malignant strokes on DWI, however, result in poor outcome after thrombolysis. We retrospectively analyzed a large cohort of DWI acquired as part of a standard MRI protocol for triage of patients at a single center over 8 years.
Methods: Consecutive patients with discharge diagnosis of ischemic stroke and documented time last known well to DWI MRI acquisition < 4.5 hours were identified. An imaging expert outlined DWI lesions on every axial slice for all MRIs to calculate corresponding lesion volumes as often-subtle changes may evade automated detection. Total DWI volumes were analyzed with respect to age, gender, TLKW and time of day.
Results: 307 stroke patients (mean age 69±17 years, 51% female) from 2004-2012 had DWI with TLKW < 4.5 hours (mean 147±62 min). DWI lesion volume (median 3.67cc) in each case varied extensively (TLKW-DWI < 1 hour (n=8) 0.40cc (0-93cc), 1-2 hours (n=126) 3.02 (0-265), 2-3 hours (n=78) 2.18 (0-103), 3-4.5 hours (n=95) 6.96 (0-227)). Only slight or negligible correlation (r=0.175, p=0.002) was noted between DWI lesion volume and TLKW-DWI time duration. DWI-negative findings < 4.5 hours occurred in 8.5% of stroke cases. Malignant strokes (>70cc) were noted in 7.5%. Older age was associated with DWI-negative strokes (mean 77 vs. 68 years, p=0.013). TLKW-DWI time duration was unrelated to DWI-negative strokes, yet malignant stroke was more common later (p=0.009). Interestingly, the majority of malignant strokes on DWI had TLKW during the daytime.
Conclusions: DWI changes are extremely variable within 4.5 hours. Most lesions are small, yet malignant strokes are not uncommon. Further work should delineate the clinical determinants of these early malignant strokes to optimize outcomes in acute ischemic stroke.
- © 2012 by American Heart Association, Inc.