Should Carotid Duplex Velocity Thresholds be Modified for Patients Undergoing Computed Tomographic Angiography?

Abstract

Purpose

The use of computed tomographic angiography (CTA) has increased dramatically whereas angiography (ANGIO) has decreased proportionally. The purpose of this study is to evaluate the impact of this trend on internal carotid artery (ICA) ultrasound velocity criteria in the vascular laboratory.

Methods

Carotid duplex quality assurance (QA) databases were queried for similar cohorts of CTA and ANGIO ≥50% and ≥70% stenoses. Optimal velocity thresholds, sensitivity and specificity for ICA peak systolic velocity (PSV), end-diastolic velocity (EDV), peak systolic ICA, and common carotid artery ratio (carotid ratio) were obtained for CTA and ANGIO groups.

Results

A total of 101 vessels were analyzed in each group. Optimal PSV threshold, sensitivity, and specificity for CTA ≥50% stenosis was 152 cm/sec, 92.1% and 94.9% and for ANGIO, 170 cm/sec, 85.9% and 91.9%, respectively. When the optimal PSV threshold for the ANGIO group was applied to the CTA group, sensitivity and specificity were 85.7% and 94.7%, respectively. In the CTA group, PSV threshold was significantly lower when used to diagnose the ANGIO group ≥50% stenosis (p = 0.0001). Optimal PSV, EDV, and PSV ratio thresholds for CTA ≥70% stenosis were 230 cm/sec, 62 cm/sec, and 2.7 and for ANGIO, 230 cm/sec, 68 cm/sec, and 3.2. Although no PSV differences were noted, when optimal EDV and PSV ratio thresholds for ANGIO ≥70%were applied to CTA ≥70%, EDV sensitivity and specificity were 80.9% and 94.7%, PSV ratio, 78.7% and 92.6%, respectively. CTA EDV and PSV ratio thresholds were statistically lower when used to diagnose ANGIO >70% stenosis (p = 0.0001).

Conclusions

Optimal PSV threshold for ≥50% and EDV and PSV ratio thresholds for ≥70% ANGIO stenosis were lower, with significant differences in sensitivity and specificity found, when used to diagnose similar CTA stenoses. Modifying angiography-based carotid duplex velocity criteria may be warranted for patients who are evaluated with CTA.

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