Assessment of carotid artery stenosis using pulse wave transit time

A prospective study has been undertaken on 24 patients to establish the relationship between the degree of internal carotid artery stenosis, as estimated by arteriography, and the pulse wave transit time in the carotid artery. The technique involves the simultaneous use of two continuous wave Doppler velocimeters, one on the carotid and one on the supraorbital artery, to measure the flow waves and hence deduce the pulse wave transit times. The measured transit times varied from 17 to 124 ms with a beat-to-beat variation of 11 per cent. The absolute transit time in any segment correlated moderately well with the estimated degree of stenosis (r = 0.68, P less than 0.001). However, normalization of the transit times, to correct for the effects of blood pressure and age, produced on improved correlation between the variables (r = 0.8, P less than 0.001). Normalization was achieved by dividing the common carotid to supraorbital transit time by the shortest transit time found between the common carotid and either the superficial temporal or brachial arteries. Significant differences in the normalized transit times were found between arteries that were diametrically stenosed by more than 50 per cent, by between 21 and 50 per cent and by 20 per cent or below. It is concluded that pulse wave transit time measurement can provide a simple and reproducible non-invasive technique for the diagnosis of varying degrees of carotid artery stenosis.