Better understanding of the interplay between underlying pathology and timing could enable better selection of patients for late interventions, one expert says.
Mismatch profile on CT perfusion has a substantial impact on the degree to which the time from stroke onset to reperfusion affects outcomes, according to research published online March 16, 2018, ahead of print in Stroke.
The study adds to mounting data that will ultimately help interventionalists determine which stroke patients are likely to benefit from mechanical thrombectomy outside of the standard 6-hour time window, researchers say.
Jenny P. Tsai, MD (Stanford University, Stanford, CA), and colleagues used data from the Computed Tomographic Perfusion to Predict Response in Ischemic Stroke Project (CRISP), in which patients underwent a baseline CT perfusion before endovascular therapy, to identify 156 patients with the mismatch profile. CT perfusion mismatch was defined as cerebral blood flow core < 70 mL and an absolute difference between the Tmax > 6s and ischemic core volumes of > 15 mL and a volume ratio of > 1.8.
The investigators further identified 108 patients (69%) as having a target-mismatch profile, defined as a mismatch profile in which the Tmax > 10s volume was ≤ 100 mL. The other 48 patients (26%) were identified as having a malignant-mismatch profile, defined as a Tmax > 10s volume > 100 mL.
The time from CT perfusion to reperfusion was associated with functional independence, defined as a 90-day mRS score of 0-2, among patients with the malignant-mismatch profile (OR 0.08; 95% CI 0.01-0.32, P = 0.003) but not among those with the target-mismatch profile (P = 0.84).
Compared to patients with target mismatch, those with the malignant-mismatch profile had significantly more infarct growth (90 mL vs 43 mL, P = 0.006) and larger final infarct volumes (110 mL vs 48 mL; P = 0.001).
“This study demonstrated that, among patients with evidence of salvageable tissue on CT perfusion who received endovascular therapy, some remain very sensitive to the effect of time from CT perfusion to reperfusion, Tsai told Neurovascular Exchange. “… Rapid in-hospital processes from imaging to reperfusion is still very important. This study is a reminder of that. Even though the window for endovascular therapy has expanded patient eligibility for consideration for endovascular therapy based on time of onset, once imaging identifies the patient as a good candidate for endovascular therapy, achieving reperfusion as early as possible is still crucial in maximizing chances for a good outcome. No matter how long since the estimated stroke onset, the pace should not slow down until reperfusion occurs.”
In a comment on the study, Ronan Motyer, MD (Beaumont Hospital, Dublin, Ireland), told NVX that these findings further confirm the outcomes of ESCAPE. “Time from stroke onset to imaging dictates eligibility for intervention; time from imaging to intervention influences outcome,” he said. “However, time has variable effects, dictated by individual pathophysiology.”
Motyer echoed Tsai’s conclusion that the study, “further reinforces the need for fast workflow and highlights the variable degree of benefit with endovascular thrombectomy, likely influenced by differences in pathophysiology amongst stroke patients,” he continued. “Superior collateral flow likely enables ‘slow progressors’ with a target mismatch to achieve good outcomes in the extended time windows.”
What remains uncertain, Motyer added, is how precisely to “measure pathophysiology and the thresholds for patient selection. . . . DEFUSE 3 and DAWN used perfusion-based imaging, while our study demonstrated success with indirect measurement using CT ASPECTS and multiphase CTA.”
“Data from this study may enable subcategorization of patients meeting inclusion criteria for intervention and aid prognostication of patients being considered for intervention,” he suggested. “It may also help inform selection of late-presenting patients.”
Source:
Tsai JP, Mlynash M, Christensen S, et al. Time from imaging to endovascular reperfusion predicts outcome in acute stroke. Stroke. 2018;Epub ahead of print.
Disclosures:
Tsai and Motyer report no relevant conflicts of interest.
