IV Alteplase Eligibility COR LOE New, Revised, or Unchanged Administration of IV alteplase in eligible patients without first obtaining MRI to exclude cerebral microbleeds (CMBs) is recommended. I B-NR New recommendation. CMBs are common in patients receiving IV alteplase, occurring in 15% to 27%.89 94 Such patients were undoubtedly included in the pivotal NINDS and ECASS III trials that established the benefits of IV alteplase treatment.48,49 Two meta- analyses of the association of baseline CMBs and the risk of sICH after IV alteplase reported that sICH is more common in patients with baseline CMBs, whereas 2 other meta-analyses and 1 multicenter study did not.89 93 In 2 studies using ECASS II sICH criteria, the rates in patients with CMBs were 5.8% and 6.5% compared with 5.3% in ECASS III.49,90,91 One study analyzing the risk of sICH in patients with CMBs detected after IV alteplase treatment reported sICH of 5% using the NINDS criteria compared with 6.4% in the NINDS tPA trials.48,94 The risk of sICH in patients with >10 CMBs (30% 47%) is consistently reported as significantly greater than in those with no CMBs (1% 4.4%). However, these data are based on <50 patients, constituting <2% of these series.90,91,93,94 No RCTs of IV alteplase in AIS with baseline MRI to identify CMBs have been conducted, so no determination of the effect of baseline CMB on the treatment effect of alteplase with CMB is available. In the absence of direct evidence that IV alteplase provides no benefit or produces harm in eligible patients with CMBs, withholding treatment on the basis of the presence of CMBs could lead to the exclusion of patients who would benefit from treatment. See Table XXI in online Data Supplement 1. 