The study of embolism in the cerebral and peripheral circulation requires imaging methods that reveal pathology in some part of the heart or circulation upstream of the occluded vessel. Technological advances over the past 10–15 years, and in particular the development of transoesophageal, epiaortic, and intravascular ultrasound has made it possible to obtain high resolution images of atherosclerotic lesions in arteries, allowing study of coronary, cerebral, and peripheral vessels as well as the aorta. For aortic disease, transoesophageal and epiaortic ultrasonography have the advantage over other imaging methods, such as computerised tomography or magnetic resonance imaging, of providing real-time images that allow for the evaluation of plaque morphology, ulceration, and mobility. The disadvantages are that transoesophageal ultrasound is semi-invasive and has a blind spot (the upper part of the ascending aorta) and epiaortic ultrasound can only be used intraoperatively.

A number of ultrasonically derived classifications of aortic atheroma has been described based on the thickness of aortic plaques and their morphology. In patients with multiple plaques, the thickness of the deepest plaque is measured. Most investigators have graded the aorta as follows: grade I, no disease or minor intimal thickening; grade II, extensive intimal thickening but without discrete measurable plaques; grade III, protruding plaques < 5 mm thick; grade IV, protruding plaques ⩾ 5 mm; grade V, any mobile atheroma.1 ,2Other variations on the theme are described with diffuse intimal thickness and small protruding plaques generally being considered as “simple” lesions, and large protruding, ulcerated or mobile lesions as “complex”.

Partly because it has been easier to study the carotid vessels, the association between carotid disease and cerebral embolism has been extensively documented, and treatment strategies continue to be evaluated. With such a diffuse arterial process, however, one would expect similar embolic associations with disease elsewhere in major arterial vessels, and …