Duration of Arterial Recanalization During Intravenous TPA Therapy: Classification and Short-term Improvement
Background: Arterial recanalization precedes clinical improvement in ischemic stroke. However sudden reperfusion may increase the chance of edema or hemorrhage. Methods: Consecutive patients given intravenous TPA were monitored using transcranial Doppler (TCD). The NIH Stroke Scale (NIHSS) was performed before bolus and at 24 hours. Patients with complete or partial recanalization according to validated criteria were analysed. Duration of recanalization was classified a priori as sudden (abrupt appearance of a normal or stenotic low resistance signal), stepwise (flow improvement over 1–29 minutes), and slow (30–60 minutes). Results: Recanalization occurred in 43 patients (age 68±17 years, NIHSS 16.8±6, median 15 points, TPA bolus at 135±61 minutes after onset). Recanalization began at 23±19 min (median 17) and completed at 42±23 min (median 35) after bolus. Duration of recanalization was 23±16 min (median 17 min). Recanalization was sudden in 5, stepwise in 23, and slow in 14 patients. Faster recanalization predicted better short term improvement (Table, p=0.03). Symptomatic hemorrhage occurred in 1 patient with stepwise recanalization at 5.5 hours after onset. Slow and/or partial recanalization with dampened flow signal was found in 53% of patients with NIHSS ≥ 10 points at 24 hours (p=0.01). Conclusions: Short duration of recanalization is associated with better short-term improvement mostly likely due to faster clot break-up and low resistance of the distal circulatory bed. Slow flow improvement and dampened flow signal are poor prognostic signs that may be useful in patient selection for interventional treatment.