Routine screening for IV tPA therapy less than 3 hours with MRI: initial clinical experience
Background: Acute MRI imaging including diffusion, perfusion, angiography, and FLAIR provides useful information in the diagnosis of stroke. It has been proposed that the stroke MRI exam may improve patient selection and outcome for tPA therapy. An alternate view holds that MRI may excessively delay times to treatment and lead to worse outcomes. To look for any evidence of adverse effects of MRI screening, we examined our initial experience using MRI as a screening exam for tPA therapy. Methods: The critical care pathway for stroke at our hospital mandates both CT and MRI for all patients under consideration for IV tPA therapy within 3 hours of onset. Delays are minimized by 24 hour in-house MRI technologists and immediate availability of both the MRI and CT scanners when a stroke code is called. Scans are monitored by a stroke neurologist and/or radiologist to minimize delays in image interpretation. MRI exclusion criteria for tPA are: (1) presence of subacute lesions not suspected from history or CT (2) normal DWI, PWI and MRA of good technical quality (3) any evidence of hemorrhage. Results: Twelve patients were treated with tPA; 4 were excluded based on MRI Results: 2 had subacute lesions, 1 had evidence of chronic hemorrhage, 1 had a normal MRI (final diagnosis: Guillain-Barre Syndrome). Four of the treated patients had no MRI because of contraindications (n=3) or scanner unavailability (n=1). One patient was treated based on MRI results only; CT was unavailable. Median door-to-needle time (MDTNT) for the 8 MRI screened patients was 83 minutes; median time-to-treatment (MTTT) was 134 minutes. Four of these 8 patients achieved a modified Rankin Score of 0 or 1 (mRS12) on follow-up. One had a symptomatic hemorrhage and died (time-to-treatment was 116 minutes). Conclusion: In this small series, door to needle times and outcomes are well within benchmark values (STARS Study: MDTNT - 96 minutes, MTTT - 164 minutes, mRS12 at outcome - 43%; G. Albers, et al, JAMA. 2000;283:1145). There is no evidence to date that MRI screening for iv tPA leads to excessive delays or worse outcomes. A larger series is necessary to demonstrate the safety and efficacy of MRI screening for IV thrombolysis.