Abstract TP64: IV tPA Treatment of Minor Stroke Using MRI Targets Rather Than Clinical Severity

Abstract

Background: It is unknown whether patients with non-disabling minor acute ischemic stroke (mAIS) at presentation benefit from IV tPA. The CT-based PRISMS trial suggested no benefit, but was inconclusive due to early termination for low enrollment. Conversely, we have observed an increasing trend in IV tPA treatment of mAIS patients screened with MRI. In this study, we sought to determine our IV tPA treatment rate of patients with mAIS and describe the frequency of MRI targets of acute ischemic stroke (AIS) for these patients stratified by clinical severity. Methods: Patients were included in this study if: 1) treated with IV tPA for AIS from 2015-2017, 2) baseline MRI, and 3) NIHSS<6. Baseline MRI was evaluated (2-rater with 3rd tie breaker) for AIS targets on DWI, PWI, GRE, FLAIR, and MRA. Patients were retrospectively categorized as “disabling” vs. “non-disabling” based on NIHSS (“non-disabling” defined as maximum 1 point each for visual fields, facial palsy, sensation, and dysarthria only). Frequency of AIS targets on MRI were compared between the two groups. Results: Of 305 patients treated with IV tPA, 140 (46%) had mAIS (NIHSS<6), 119 of 140 (85%) had baseline MRI, 53 of 119 (45%) were “non-disabling.” There was no difference in presence of these imaging targets between “disabling” vs. “non-disabling” mAIS patients: DWI lesion, 86.4% vs. 88.7%, p=0.705; PWI lesion, 80.3% vs. 79.2%, p=0.685; PWI/DWI mismatch, 62.1% vs. 50.9%, p=0.337; FLAIR HVS, 48.5% vs. 43.4%, p=0.775; MRA LVO, 24.2% vs. 26.4%, p=0.829, MRA LVO location, p=0.91. There was a trend toward greater visualization of GRE thrombus in the “disabling” group: 40.9% vs. 24.5%, p=0.060. “Non-disabling” mAIS patients treated based on MRI target accounted for 17% of all IV tPA-treated patients. Conclusions: In MRI-screened patients with mAIS, there is no difference in frequency of AIS imaging targets in those with “disabling” vs. “non-disabling” deficit. These findings suggest that these MRI targets rather than clinical severity could be used to drive the decision to treat mAIS patients with IV tPA and greatly expand the pool of patients for thrombolytic therapy. The similarities of these imaging targets in mAIS patients with and without disabling deficit can be used to justify an MRI-based treatment trial.