Attempts to establish that patients with a longer duration of ischemic symptoms benefit from thrombolysis by tPA have varied in success but have favored an effect up to 4.5 h as noted below. In some patients with basilar artery occlusion and coma of brief duration and those without extensive thrombosis, prompt tPA treatment has at times also resulted in an overall improvement in neurologic function, but there were numerous exceptions. Adapted from guidelines issued by the American Heart Association are the generally agreed upon inclusion and exclusion criteria for the use of intravenous tPA as shown in Table 33-6. Intracranial and systemic bleeding is, of course, the great concern and a minor but interesting point is that some patients, who had been receiving angiotensin-converting enzyme inhibitors for the treatment of hypertension, seem to display angioneurotic edema as a side effect of tPA.
Generally excluded from thrombolysis are those patients in whom the deficit is either very small (e.g., hand affected only, dysarthria alone, minor aphasia), rapidly improving, or more importantly, is so large as to implicate almost the entire territory of the middle cerebral artery. Many centers have expanded their practices beyond the confines of the initial NIH study, treating patients older than age 80 years and some with large strokes. Also ambiguous is the treatment with tPA of patients with acute stroke in whom the referable cerebral vessels are entirely patent. Often, the patency of the vessel is not known.
Public health education should increase the numbers of stroke patients who seek early attention and thus raise the proportion who are eligible for tPA treatment.
Thrombolytic substances injected intraarterially (thrombolysis), or mechanical lysis for disruption or removal of an intravascular clot (thrombectomy) can in some instances restore blood flow of the middle cerebral and basilar arteries. There is an incidence of reocclusion of the treated vessel. The more recent approaches involve the use of a device that retrieves clots from the intravascular lumen. Whereas the initial trials were conducted in patients up to 6 h after stroke, more recently this window has been extended to 16 to 24 h with proper patient selection. The main criteria for selection of patients for thrombectomy in these trials have been: the presence of occlusion of the intracranial internal carotid, middle, or anterior cerebral arteries, and a mismatch between the extent of the stroke deficit and the volume of ischemic but not yet infarcted tissue, as judged either clinically or by imaging criteria (Albers et al, Kidwell et al, and Nogueira et al). The rate of symptomatic intracranial hemorrhage has been similar to that for intravenous thrombolysis, approximately 6 percent. As all of these trials have enrolled patients with anterior circulation strokes, the problem of reversing the neurologic deficit from acute basilar artery thrombosis by the use of thrombectomy is being studied.