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Optical coherence tomography (OCT) is widely used for accurate coronary stent sizing. The impact of coronary tortuosity or stiff guide wires (needed to deliver stents in tortuous segments) on the accuracy of OCT in assessing coronary dimensions is not known. This study sought to quantify the influence of guide wire weight on the accuracy of OCT in determining diameters.
Coronary measurements were determined in 20 patients with tortuous coronaries using OCT before and after removal of a supportive guide wire. This phenomenon was further assessed in a coronary model using variable diameters and two different wire weights.
Coronary diameter measurements decreased by 0.1-12% following removal of the guide wire. There was a positive correlation between vessel diameter and effect of guide wire removal. In a model, mean lumen diameter was overestimated by the introduction of tortuosity (flexible wire (FW) vs. supportive wire (SW) for tube sizes 1.7mm: +0-0.1mm vs. +0.1-0.2mm, P=0.31; 2.7mm: +0.02-0.17mm vs. +0.18-0.46mm, P<0.01; 3.2mm: +0.35-0.39mm vs. +0.77-0.91mm, P<0.001; 4.8mm: +0.4-0.69mm vs. +0.88-1.05mm, P<0.001; unpaired t-tests). Overestimation of diameter could be minimised by measuring luminal images with the least eccentric catheter position.
This data suggests that OCT overestimation of diameter should be considered when performing coronary intervention in tortuous vessels. The effect is augmented by increased wire stiffness within the lumen and can be minimised by removal of the guide wire or selecting images with low catheter eccentricity.