A patient was found to have watershed infarct after cardiac arrest.
The MRI (DWI - diffusion weighted image) image shows watershed infarct involving an internal border zone (LCA abd MCA) and cortical border zone (MCA and PCA). They are between adjacent arterial perfusion beds.
The reduction in perfusion can be due to pump failure caused by cardiac arrest or arrhythmia, or reduced cardiac output due to a variety of causes. In this case, the ecg showed prolonged QT, and a tachyarrhythmia with QRS complexes of changing amplitute (Torsades de pointes). This tachyarrhythmia caused the hypoperfusion and the watershed infarct.
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