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Ann Thorac Surg 2000;70:1795
© 2000 The Society of Thoracic Surgeons

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Scientific abstract

Diffusion-weighted brain magnetic resonance imaging in patients with neurologic complications after cardiac surgery

Departments of Neurology and Radiology, Johns Hopkins Hospital, Baltimore, Maryland, USA

Introduction. Clinically evident stroke occurs in 2% to 5% of patients after cardiac surgery, but more subtle cerebral ischemia may be missed by computed tomography (CT) or standard magnetic resonance imaging (MRI). Diffusion-weighted MRI (DWI) is more sensitive and specific for acute stroke, and perfusion-weighted MRI (PWI) can demonstrate cerebral perfusion abnormalities in the absence of infarction.

Methods. We performed a review of DWI and PWI studies in patients prospectively identified with neurologic complications after cardiac surgery.

Results. We identified 14 patients who had DWI studies within 15 days after cardiac surgery (12 coronary artery bypass grafts, one mitral valve replacement, one aortic dissection repair). Six patients presented with focal neurologic symptoms, 4 with encephalopathy, and 4 with encephalopathy plus focal deficits. Pattern of stroke on DWI included: widespread emboli (n=6), single embolus (n=1), watershed infarction (n=3), and no acute lesion (n=4). DWI showed infarcts in 5 of 9 patients with normal CT; in 4 of 5 patients with stroke on CT, DWI revealed numerous other lesions. PWI in 4 patients were normal in 2 and showed diffusion-perfusion mismatch in 2 (PWI > DWI). Both patients with mismatch had intermittent or fluctuating symptoms that improved with increase of blood pressure.

Conclusions. In over 40% of patients reviewed, DWI revealed a pattern suggestive of widespread, multiple emboli, most of which were very small and not evident on CT or inconspicuous on standard MRI. Some patients with encephalopathy, however, had no DWI lesion. PWI revealed 2 of 4 patients with persistent cerebral perfusion defects amenable to treatment.

Issues. Stroke, emboli, diffusion, and perfusion-weighted MRI.

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