As a stroke physician gets ready to treat a stroke with tPA, hemorrhagic conversion (see below) is always in her mind. To understand this, lets first review what happens inside the brain during a typical ischemic stroke.
A stroke is caused by the blockage of blood flow to a part of the brain, which causes a large area of tissue to become oxygen-hungry, and the cells that make up that area begin to die. Over time, fewer and fewer cells are left to be saved by stroke treatments, and after most of the cells have died, treating the stroke is no longer helpful and can actually turn the ischemic stroke into a hemorrhagic one. This event is known as a hemorrhagic conversion
How is this possible? Most emergent treatments of ischemic stroke aim to return blood flow to the ischemic area by dissolving the stroke-causing blood clots. But just a few hours after an area of brain tissue has died, it loses its ability to retain blood inside of the arteries, increasing the risk that a large hemorrhage will occur if blood flow were to be returned. This type of bleeding into dead tissue is called a hemorrhagic conversion. Approximately 6% of all stroke cases treated with intravenous tPA, a powerful blood clot-busting medicine, experience a hemorrhagic conversion.
This prospect of hemorrhagic conversion is one of the main reasons why intravenous tPA and other similar stroke treatments can only be used within a certain time window after the onset of symptoms.
Learn to recognize the symptoms of a stroke
Source
Götz Thomalla, MD; Jan Sobesky, MD; Martin Köhrmann, MD; Jochen B. Fiebach, MD; Jens Fiehler, MD; Olivier Zaro Weber, MD; Anna Kruetzelmann, MD; Thomas Kucinski, MD; Michael Rosenkranz, MD; Joachim Röther, MD Peter D. Schellinger, MD, PhD Two Tales: Hemorrhagic Transformation but Not Parenchymal Hemorrhage After Thrombolysis Is Related to Severity and Duration of Ischemia
MRI Study of Acute Stroke Patients Treated With Intravenous Tissue Plasminogen Activator Within 6 Hours Stroke 2007;38:313
