P420Can we measure carotid plaque volume and does it matter?

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Stroke is the third leading cause of death and the leading cause of disability with 150,000 sufferers/year in the UK. Carotid disease causes 30% of ischaemic strokes, probably due to embolism of atherosclerotic material. Severity of stenosis measured by duplex is currently the indication for surgery but is a poor predictor of stroke: asymptomatic carotid stenosis >70% predicts an annual stroke risk of under 2%. As stenoses may merely be a surrogate for carotid plaque volume (CPV), we investigated the relationship between CPV and symptoms in carotid disease.

Plaque volume index on preoperative duplex was compared with a precise measure of the operative specimen using an Archimedes suspension method in 52 patients undergoing carotid endarterectomy. A detailed history on risk factors and cerebral symptoms was recorded.

Plaque volume index underestimated CPV by mean ( ± sd) of 0.41 ± 0.49cm3 with a poor correlation of r = 0.49 (p < 0.05). Mean CPV for stroke, TIA, amaurosis fugax and asymptomatic patients were 1.26 ± 0.65, 1.20 ± 0.52, 1.16 ± 0.25and 0.75 ± 0.27cm3 respectively with the 36 symptomatic having significantly larger CPV at 1.21 ± 0.56cm3 than that of 0.79 ± 0.26cm3 in the 16 asymptomatic patients (p>0.01). Acutely symptomatic patients had significantly larger CPV with a mean of 1.32 ± 0.54cm3 than that of asymptomatic and symptomatic patients of more than six weeks with a mean of 0.74 ± 0.28 and 0.76 ± 0.2cm3 respectively.

CPV can be measured accurately using an Archimedes suspension method and was strongly associated with symptoms in patients undergoing carotid surgery. As all our patients had >70% carotid stenoses, CPV clearly has greater potential to predict symptom status. If 3-D imaging measures CPV accurately, the indication for carotid surgery may need to be reconsidered.

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