Author Response: Cerebral Microbleeds and Treatment Effect of Intravenous Thrombolysis in Acute Stroke: An Analysis of the WAKE-UP Randomized Clinical Trial

We are grateful for the interest in our article on the treatment effect of alteplase in acute ischemic stroke patients with preexisting cerebral microbleeds (CMBs).¹ The readers point out that new lesions are observed on susceptibility-weighted imaging (SWI) in patients with artificial heart valves that meet the imaging criteria of CMBs and suggest that these lesions should be differentiated from CMBs associated with small vessel disease to better identify patients with an increased bleeding risk.² Of interest, a previous study showed that new CMBs occurring in acute ischemic stroke patients after receiving IV thrombolysis (IVT) were indeed associated with an increased risk of IVT-related hemorrhagic complications.³ On the other hand, new CMBs were not associated with an increased risk of bleeding in patients undergoing cardiac surgery.^2,4 However, IVT may constitute a different bleeding risk than cardiopulmonary bypass and extracorporeal membrane oxygenation, or a prolonged intensive care unit stay. The question of whether CMBs in patients with artificial heart valves represent a different pathophysiologic entity with a different bleeding risk merits further research and would profit from histopathology studies and observational studies in stroke and nonstroke cohorts with long-term follow-up.