Therapeutic Applications In Acute Ischemic Stroke

IV rtPA is currently the only Food and Drug Administration (FDA)-approved therapy for ischemic stroke within 3 hours of symptom onset (8). Noncontrast CT is the first-line imaging test for differentiating hemorrhagic from ischemic events. Based on the time of onset and clinical and CT examinations, rtPA can be given without confirmation of the presence of an arterial occlusion (8) . Thrombolytic treatment without confirmation of arterial occlusion has been

Figure 4 The most typical pattern of an acute MCA occlusion and TIBI flow grades. Some residual flow signals can be seen at distal M1 or proximal M2 MCA segments represented as minimal, blunted, or dampened TIBI flow grades. Flow diversion means that the ACA MFV is greater than MFV in the proximal MCA, and this finding serves as a confirmatory criteria. Abbreviations: MCA, middle cerebral artery; MFV, mean flow velocity; TIBI, thrombolysis in brain ischemia; ACA, anterior cerebral artery.

Figure 4 The most typical pattern of an acute MCA occlusion and TIBI flow grades. Some residual flow signals can be seen at distal M1 or proximal M2 MCA segments represented as minimal, blunted, or dampened TIBI flow grades. Flow diversion means that the ACA MFV is greater than MFV in the proximal MCA, and this finding serves as a confirmatory criteria. Abbreviations: MCA, middle cerebral artery; MFV, mean flow velocity; TIBI, thrombolysis in brain ischemia; ACA, anterior cerebral artery.

criticized (69). More centers are now attempting to employ vascular imaging to determine the presence, or persistence, of occlusion or reocclusion that has been linked to poor prognosis and that may necessitate further (currently experimental) intra-arterial interventions (70,71). Various tests can be used for this purpose, including invasive digital subtraction angiography, magnetic resonance angiography, CT angiography, and ultrasound (72,73). Ultrasound has the advantage of being a quick and inexpensive method for the real-time assessment of vessel patency and monitoring at the bedside. The key to the application of TCD in the often restless acute stroke patient is a "fast-track" insonation protocol (74). An experienced sonographer can use this method, guided by the physician's clinical assessment, to determine the presence and location of intracranial occlusion within minutes. Most studies can be done along with blood draws and neurologic assessment and can be completed within 15 minutes. A typical MCA-occlusion pattern (Fig. 4) can be detected in two minutes in the presence of good temporal windows (authors' personal observations). Bedside assessment should begin with TCD, as acute arterial obstruction that is responsible for cerebral ischemia is almost always intracranial. Once completed, the TCD examination can be supplemented with a rapid carotid/vertebral duplex assessment to determine the presence of a >50% extracranial stenosis, or thrombus, which is often the cause of artery-to-artery embolism or hypoperfusion. As compared with emergency catheter angiography, the accuracy of combined intracranial and extracranial Doppler-duplex examination, performed by expert sonographers in the emergency room, can be 100% for detection of lesions amenable to intervention (75).

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