DETECTION OF SUBCRITICAL ARTERIAL STENOSES BY HYPEREMIC DOPPLER

Objectives: This study assessed the potential of hyperaemic Doppler to detect sub-critical stenoses using a flowrig model. Methods: Pulsatil e flow of a blood substitute was produced in a compliant circuit. A ca daver carotid artery, constricted by a silk suture produced a variable , focal stenosis. Forty-seven stenoses were created in five arteries. Pressure gradients and Doppler measurements were recorded simultaneous ly across each stenosis at low (200ml/min) and high (400ml/min) flow r ates. The change in peak velocities between the arterial segment 2cm p roximal to the stenosis (V1), and the stenotic jet (V2) were used to c alculate three Doppler indices: (i) V2/V1 ratio, (ii) V2-V1 difference , (iii) a modified 'Bernoulli' value. A high flow pressure gradient of greater than or equal to 15% of the resting distal pressure (%Delta P ), represented a significant stenosis. Results: There was improved cor relation between Doppler indices and %Delta P at high flow (r = 0.87 t o 0.88) compared to low flow races (r = 0.81 to 0.84). Optimum V2/V1 c ut off values were determined fry receiver operator characteristic (RO C) curve analysis. At low flow five sub-critical stenoses were not det ected (sensitivity 82.8%) yet all but one of these lesions were identi fied at high flow (sensitivity of 96.6%). The V2-V1 and Bernoulli indi ces did not improve on the discriminant ability of the V2/V1 ratio. Co nclusions: The V2/V1 ratio is sensitive to haemodynamic changes at enh anced flow rates across ideal arterial stenoses. The potential of hype raemic Doppler to detect sub-critical lesions and so avoid intraarteri al pressure measurements deserves further in vivo study.