Continuous magnetic resonance perfusion imaging acquisition during systemic thrombolysis in acute stroke

Early recanalization and increase in collateral blood supply are powerful predictors of favourable outcome in acute ischaemic stroke. The factors contributing to the heterogeneous response to intravenous thrombolysis therapy in individual patients, however, are not fully understood. The on-going single-centre 'MR perfusion imaging during thrombolysis' study uses repetitive arterial spin labelling (ASL) measurements to characterize the haemodynamic processes in acute stroke during therapy. The first milestone was to develop an appropriate infrastructure for thrombolysis in the magnetic resonance imaging (MRI) scanner without time delay and ensuring optimal patient safety and care.

Between February and December 2011, 16 patients with acute neurological symptoms suggestive of hemispheric stroke within 4.5 h after symptom onset were included. In addition to clinical data, we documented the time from onset to arrival at the hospital, start and duration of MRI examination, start of thrombolytic therapy, and complications. The decision to thrombolyse was made after a routine stroke MRI protocol. During the 60-min systemic thrombolysis, repetitive ASL perfusion imaging was acquired, providing non-invasive information on cerebral perfusion. Continuous ECG monitoring, pulse oximetry, blood pressure measurements every 5 min, and short neurological assessments every 15 min were performed in every patient.

The median initial NIHSS score of the patients presenting with a mean of 84 min after onset was 4 (range 2-18). MRI examination was initiated within a mean of 45 min after arrival at the hospital. Five patients identified as stroke mimics were not treated with recombinant tissue plasminogen activator (rt-PA), and in 1 case with basilar artery occlusion bridging therapy was performed outside the scanner. In the remaining 10 patients, rt-PA therapy was started in the scanner directly after decision making on the basis of clinical information and baseline MRI. The mean door-to-needle time was 60 min (range 44-115) including approximately 10 min needed for acquiring informed consent. While 4 patients required antihypertensive treatment, no relevant complications were encountered.

Fast and safe medical care in patients during systemic thrombolysis in the MRI scanner is feasible. Despite the process of obtaining informed consent, with a dedicated and experienced stroke team the door-to-needle time can be kept in a range recommended by current guidelines. Continuous real-time information about the dynamics of cerebral perfusion from ASL perfusion in acute stroke patients undergoing thrombolysis may provide additional information for the understanding of the events following acute arterial obstruction and its course.