Analysis of our results of intra-arterial thrombolysis in patients of acute brain ischemia revealed the good outcomes were ssociated with less severe hypoperfusion on presentation, successful recanalization and early treatment of the occlusion. These observations support Warach´s et al[11] recently presented 4-factor model of tissue viability thresholds in acute stroke which include: 1) Time (duration of hemodynamic changes from onset), 2) Hemodynamic factor (degree of changes of cerebral blood flow (CBF), cerebral blood volume (CBV) or mean transit time (MTT), 3) Tissue factor (local metabolic, genetic, vascular or structural changes), 4) Intervention factor (type to reperfusion or neuroprotective therapies). Our data support the fact that the best clinical results were obtained when
1. The Time factor was at a minimum, best if revascularization was achieved in less than three hours of the onset on the ischemia. Fig. 10.
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Figura 10
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Pre and Post arterial Thrombolysis NeuroSPECT images demonstrating the extent of damage recovery. (Pt.# 1 Table 1).
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2. The Hemodynamic factor, the degree of hypoperfussion was not as severe, between 2 and 4 SD below the mean uptake.
3. The Intervencional factor achieve satisfactory revascularization of the occluded vessel.
Based on these three parameters, we were able to anticipate the evolution of our patients.
There are a variety of known predictors of poor clinical outcome and increased risk of parenchymal hematoma, including hyperglycemia, stroke severity, elevated pretreatment blood pressure, very early and extensive hypodensity on brain CT that exceeds on third of the middle cerebral artery (MCA) territory[12-14]. We present another possible predictor of poor outcome, namely severe cerebral hypoperfusion as defined as below 8 SD of the mean uptake of HMPAO in the Neuro-SPECT scan.
Furthermore, to the authors knowledge this paper represents the first published report of cerebral blood flow (CBF) changes studied by NeuroSPECT in response to intra-arterial thrombolysis treatment of an ischemic stroke. The changes in CBF depicted on the before and after endovascular therapy scans confirms that thrombolysis positively alters the natural history and outcome of a significant ischemic brain lesion. Recently Parson et al reported the MRI Diffusion-Perfusion changes in studies performed before and after thrombolysis in patients with acute ischemic stroke[16].
We believe that Tc99m-HMPAO SPECT brain cortical uptake examination is an underutilized and extremely useful method for evaluating ischemic cerebrovascular disease. Its infrastructure requirements include a standard gamma camara, already present in many hospitals, and much less expensive than the new MRI or Multislice CT machines. The radiopharmaceutical HMPAO labeled with Tc99mm is widely available, and is much less expensive than the cyclotron labeled PET isotopes. Furthermore, the Tc99m-HMPAO isotope can be quickly prepared and administered in time before the initiation of therapy. The therapeutic intervention was not delayed by the HMPAO injection, and imaging was deliberately performed after the completion of the thrombolysis treatment as to not delay the treatment of the patient. This is impossible to achieve with the cyclotron labeling of the isotope in the PET examination. Furthermore, the post-processing of the NeuroSPECT data is also relatively simple, performed by an automated Neurogam program available at in many laboratories.
