tPA-Associated Reperfusion After Acute Stroke Demonstrated by SPECT

Abstract

Purpose-The aim of our study was twofold: to determine the frequency and magnitude of perfusion defect in stroke patients who qualify for rtPA therapy within 3 hours of stroke onset and to determine the ability of rtPA to improve perfusion by 24 hours. Subjects and Methods-Patients with suspected hemispheric stroke who fulfilled entry criteria into the National Institute of Neurological Disorders and Stroke (NINDS) rt-PA Stroke Study and also had pretreatment injection of 99m Tc-HMPAO, with single-photon emission computed tomography (SPECT) performed using a triple-head camera at baseline and 24 hours, were included. Results-All 12 patients who qualified for rtPA therapy had perfusion defects on baseline SPECT (SPECT graded scale [SGS] score range, 16 to 79). MeanϮSD perfusion defect was comparable in rtPA (nϭ4)versus placebo (nϭ5) A lthough rtPA therapy within the first 3 hours after the onset of acute stroke symptoms results in improved outcome, the urgency of this therapy precludes extensive diagnostic studies before treatment. Therefore, in the NINDS study that demonstrated the efficacy of rtPA, there was no requirement to demonstrate a perfusion defect prior to treatment. Furthermore, while it is assumed that the effectiveness of rtPA was due to its ability to improve reperfusion during the immediate poststroke period, this was not documented by comparing baseline with 24-hour studies of cerebral blood flow in the rtPA versus placebo groups. At our center, which was one of the participants in the NINDS rt-PA Stroke Study, we tried to obtain SPECT cerebral perfusion studies at baseline and after 24 hours in as many patients as possible during the study. We report the baseline results in all 12 patients who had SPECT scans carried out within 3 hours of symptom onset and the baseline compared with 24-hour SPECT studies in all 5 placebo-treated and 4 rtPA-treated patients. Subjects and Methods Selection of PatientsAll patients admitted to Hermann Hospital (Houston, Tex), where we carried out the NINDS rtPA study, were considered for inclusion.The inclusion and exclusion criteria for the NINDS study have been published 1 and for the most part were the inclusion and exclusion criteria for the present SPECT analysis, because all patients studied with SPECT were being considered simultaneously for inclusion into the NINDS rtPA trial. In addition, to be included in this SPECT substudy, all patients had to receive the injection of isotope ( 99m Tc-HMPAO) for SPECT within 3 hours of symptom onset but before rtPA administration, all had to have technically adequate SPECT scans carried out at baseline and again after 24 hours, and all had to have suspected hemispheric infarcts. Of the 12 patients meeting these criteria and included in this analysis, 8 were randomized into the NINDS rtPA versus placebo study and one was treated with openlabel rtPA soon after the study was completed. Three were not treated with thrombolytics. Some of these patients were included in a previous publication 2 that validated our SPECT meth...

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“…Similar treatment effects have been found after six months and one year poststroke [3]. The benefit of rt-PA is thought to be due to the early recanalisation of occluded arteries, resulting in increased cerebral reperfusion [4] and a subsequent reduction of lesion volume [5]. The sooner thrombolytic treatment is administered after stroke,the greater the efficacy of the treatment [6,7].…”

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PET imaging in ischemic cerebrovascular disease: current status and future directions

“…4): reperfusion significantly improves in rtPA-treated patients compared to controls [46] . The volume of tissue salvaged by reperfusion was determined by H 2 15 O-PET within 3 h of stroke onset and compared with the volume of infarction assessed on MRI 3 weeks after the stroke [47] .…”

Radionuclide Imaging in Ischemic Stroke

“…5): reperfusion was significantly increased in rtPAtreated patients compared with controls (64). The volume of tissue salvaged by reperfusion was established in a study in which CBF, as determined by H 2 15 O PET within 3 h of stroke onset, was compared with the volume of infarction determined on MR imaging 3 wk after the ictus (65).…”