CT Perfusion May Increase Time to Reperfusion for Patients With Acute Ischemic Stroke

NEW ORLEANS—Patients who were selected for endovascular stroke interventions on the basis of CT perfusion (CTP) imaging experienced significantly longer times between CT acquisition and groin puncture and reperfusion than patients selected on the basis of noncontrast CT imaging did, according to research presented at the 2012 International Stroke Conference. The mean time between CTP and reperfusion was 223 minutes, and the mean time between noncontrast CT and reperfusion was 175 minutes.

Patients selected for endovascular intervention on the basis of CTP experienced symptomatic hemorrhage at a rate of 6.8%, compared with a rate of 6.6% for patients selected on the basis of CT. Approximately 37% of patients who received intervention on the basis of CTP had good outcomes, compared with nearly 39% of patients imaged with noncontrast CT. Final infarct volume for patients selected through CTP was 80 cm³, compared with 88 cm³ for patients selected through noncontrast CT.

The lack of significant differences in these parameters between the patient groups suggests that CTP may not improve the selection of patients with acute ischemic stroke for endovascular reperfusion therapies, according to Rishi Gupta, MD, Associate Professor of Neurology at Emory University School of Medicine in Atlanta.

Comparing Two Imaging Methods of Patient Selection
Dr. Rishi and his colleagues retrospectively analyzed the clinical outcomes, hemorrhage rates, and final infarct volumes of 418 patients treated for acute ischemic stroke at seven institutions between September 2009 and December 2011. A total of 191 patients were selected on the basis of CTP, and 227 were selected on the basis of noncontrast CT. All patients were treated less than eight hours after the onset of symptoms. Good outcomes were defined as modified Rankin scale (mRS) scores between 0 and 2, and bad outcomes were defined as mRS scores greater than 2.

Patients’ mean age was 67, and their mean NIH Stroke Scale (NIHSS) score was 18. Baseline characteristics such as age, site of vascular occlusion, and pretreatment NIHSS score did not differ between the two groups of patients.

CT Perfusion Does Not Ensure a Good Outcome
The overall successful reperfusion rate among patients was 68%. Approximately 34% of patients had asymptomatic hemorrhages, and 6% had symptomatic hemorrhages. The mortality rate was 26% for the entire cohort, and 37% had good clinical outcomes.

Patients selected using noncontrast CT had significantly higher NIHSS scores than the patients selected using CTP. The former patients also were more likely to have diabetes mellitus and carotid terminus occlusions. “To try to balance the NIHSS score difference between the two groups, we looked at only the 70% of the population with M1 occlusions. In the M1 MCA occlusion subgroup, there were no differences in outcomes when comparing noncontrast CT selected patients to CTP selected patients,” said Dr. Gupta.

The researchers also performed a subgroup analysis of patients with ASPECTS greater than seven. Of 198 patients in that group, 173 patients had a 90-day follow up outcome. Of these 173 patients, 47% were noted to have a good clinical outcome, which is a better result than that of the whole cohort, noted Dr. Gupta.

To identify independent predictors of good clinical outcomes, the investigators adjusted the variables for age, NIHSS score, status of reperfusion, and systematic hemorrhage. They found no statistically significant correlation between obtaining a CTP and experiencing a good clinical outcome.

“There are inherent limitations for retrospective, exploratory studies, but the utilization of multimodal CT imaging does lead to significant delays with endovascular treatments,” observed Dr. Gupta. “Additional imaging did not necessarily translate to better clinical outcomes, and the results of this analysis suggest that a prospective study comparing these two modalities may require a substantially larger cohort of patients to find a difference. Clinicians should consider the context of when to order advanced modality imaging in determining which patients are best suited for endovascular therapy,” he concluded.

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