Patients with acute stroke treated with intravenous tPA 3-6 hours after stroke onset: correlations between MR angiography findings and perfusion- and diffusion-weighted imaging in the DEFUSE study

Abstract

Purpose: To study magnetic resonance (MR) angiography findings in patients with acute stroke treated with intravenous tissue plasminogen activator (tPA) in relationship to perfusion- and diffusion-weighted imaging changes and clinical outcome.

Materials and methods: Patients treated with intravenous tPA 3-6 hours after stroke onset (with informed consent) were evaluated in a HIPAA-compliant multicenter prospective study approved by all institutional review boards. MR imaging and MR angiography studies were performed before and 3-6 hours after treatment. MR angiography studies that were technically adequate at both time points were evaluated for occlusion, decreased flow, any early recanalization, and degree of recanalization. These results were compared with favorable clinical response (an improvement in National Institutes of Health Stroke Scale score of >or=8 points at 30 days or a modified Rankin scale score of 0 or 1 at 30 days) in patients with and those without mismatch between perfusion- and diffusion-weighted imaging at baseline.

Results: Seventy-four patients were enrolled in the initial investigation; pre- and posttreatment MR angiography studies were both technically adequate in 62 patients. MR angiography demonstrated occlusion or decreased flow in 46 patients. Patients with isolated middle cerebral artery (MCA) occlusion and early recanalization at MR angiography had higher rates of favorable clinical response than those with tandem internal carotid artery-MCA occlusion and early recanalization (P = .05). Any early recanalization was not associated with favorable clinical response, but degree of recanalization did correlate with favorable clinical response (P = .048). Favorable clinical response was more frequently seen in patients with mismatch between perfusion- and diffusion-weighted imaging findings at baseline who experienced early recanalization than in those who did not have early recanalization (odds ratio = 6.2; 95% confidence interval: 1.3, 30.2; P = .021). No relationship between early recanalization and favorable clinical response was seen in patients without mismatch.

Conclusion: Early recanalization seen at MR angiography before and after treatment coupled with diffusion- and perfusion-weighted imaging data may predict clinical outcome in patients with stroke treated with tPA 3-6 hours after symptom onset.

Figure 1:

Example baseline MR images show malignant profile at diffusion-weighted imaging (top left) and perfusion-weighted imaging (top right) and target mismatch profile at diffusion-weighted imaging (bottom left) and perfusion-weighted imaging (bottom right). Color map data shows T_max delay times in 2-second intervals. The malignant profile was defined as a baseline diffusion-weighted imaging volume of 100 mL or greater and/or a large and severe baseline perfusion abnormality (perfusion-weighted imaging volume with T_max ≥ 8 seconds, ≥100 mL). The target mismatch profile was defined as a mismatch that did not satisfy the conditions of the malignant profile.

Figure 2:

Maximum intensity projection MR angiograms in three patients show normal MCA M1 flow (left), decreased flow in the left MCA M1 branch (middle), and occlusion in the left MCA M1 branch (right).

Figure 3:

Flowchart of patients in study. MM = mismatch, MRA = MR angiography.

Figure 4:

Graph shows odds ratio (OR) for favorable clinical response among patients who experienced recanalization compared with patients without recanalization in the same group. Values to the right of the vertical line indicate a more favorable clinical response, while values to the left indicate a less favorable response. An odds ratio greater than 1.0 indicates increased odds of a favorable clinical response. For the odds ratio for favorable clinical response among patients with mismatch versus patients without mismatch, P = .026. For the odds ratio for favorable clinical response among patients with target mismatch versus patients without target mismatch, P = .008. CI = confidence interval, MM = mismatch, TMM = target mismatch. *P = .021. **P = .015.