Imaging modality-dependent carotid stenosis severity variations against intravascular ultrasound as a reference: Carotid Artery intravasculaR Ultrasound Study (CARUS)

Abstract

Purpose Different non-invasive and invasive imaging modalities are used to determine carotid artery stenosis severity as a principal parameter in clinical decision-making. We compared stenosis degree obtained with different modalities against intravascular ultrasound (IVUS). Methods 300 consecutive patients (age 47–83 years, 192 men, 68% symptomatic) with carotid artery stenosis of “≥50%” referred for potential revascularization received as per study protocol (i) duplex ultrasound (DUS), (ii) computed tomography angiography (CTA), (iii) invasive quantitative angiography (iQA) and (iv) the vascular imaging gold standard, IVUS. Correlation of measurements with IVUS (r), proportion of those concordant (within 10%) and proportion of under/overestimated were calculated along with recipient-operating-characteristics (ROC). Results For IVUS area stenosis (AS) and IVUS minimal lumen area (MLA), there was only a moderate correlation with DUS velocities (peak-systolic, PSV; end-diastolic, EDV; r values of 0.42–0.51, p < 0.001 for all). CTA systematically underestimated both reference area and MLA (80.4% and 92.3% cases) but CTA error was lesser for AS (proportion concordant-57.4%; CTA under/overestimation 12.5%/30.1%). iQA diameter stenosis (DS) was found concordant with IVUS in 41.1% measurements (iQA under/overestimation 7.9%/51.0%). By univariate model, PSV (ROC area-under-the-curve, AUC, 0.77, cutoff 2.6m/s), EDV (AUC 0.72, cutoff 0.71m/s) and CTA-DS (AUC 0.83, cutoff 59.6%) were predictors of ≥ 50% DS by IVUS (p < 0.001 for all). Best predictor, however, of ≥ 50% DS by IVUS was iQA densitometry (AUC 0.87, cutoff 68%, p < 0.001). On multivariate model, however, CTA came as the sole independent non-invasive diagnostic modality (p = 0.008). Conclusion IVUS validation shows significant imaging modality-dependent variations in carotid stenosis severity determination.