Improved Accuracy of Lesion Length Assessment During Percutaneous Coronary Intervention Using a New Vessel Caliper

R Wolyn, SR Dixon, J Korotko, SL Almany, RR Huang, WW O'Neill, Division of Cardiology, William Beaumont Hospital, Royal Oak, MI.

Background: Accurate assessment of lesion length is important during intracoronary stenting to ensure adequate lesion coverage, minimize the need for deployment of additional stents, and reduce the risk of restenosis associated with long stenting. However, assessment of lesion length using visual estimation or quantitative coronary angiography can be unreliable. The purpose of this study was to evaluate the accuracy of a new method of lesion length measurement using a simple hand-held vessel caliper.

Methods: The vessel caliper (Accumed Systems, Inc., Ann Arbor, MI) is attached to the proximal end of the balloon catheter. Using fluoroscopic guidance, length is recorded by withdrawing the conventional angioplasty guide-wire (fixed to a sliding ruler) between the desired angiographic landmarks. Measurements were performed in a bench-top coronary model (using radiopaque markers of known distance as reference) and in 8 patients undergoing elective percutaneous coronary intervention. In the latter, caliper-derived length measurements were compared to visual estimates and intra-vascular ultrasound (automated pullback) measurements of length. Statistical analysis of correlation was performed using Pearson Correlation test and mean difference between measurements indicating degree of accuracy was calculated using Wilcoxon Signed rank test.

Results: In the bench-top model caliper-derived measurements correlated well with known reference distances regardless of the angiographic projection (r=0.99 p<0.001, mean difference D -0.31 ± 1.28 p=0.03) whereas QCA derived lengths were strongly influenced by vessel foreshortening: in best view r=0.98 p<0.001, mean difference D -2.14 ± 1.21 p=0.005; in foreshortened view r=0.988 p<0.001, mean difference D 9.29 ± 5.19 p=0.005). Caliper measurements performed during percutaneous interventions showed excellent correlation with IVUS derived distances (r=0.98, p<0.001, interclass correlation 0.98; mean difference D 0.25 ± 1.7). However, there was a poor correlation between IVUS distance and best visual estimates of length (r=0.69, p<0.001: interclass correlation 0.69; mean difference D 0.72 ± 7.97).

Conclusion: This new caliper device provides an accurate method of length measurement, which is superior to visual or angiographic determination of length regardless of angiographic projection used. The technique is simple and inexpensive compared to IVUS, and may have important applications not only in conventional stenting, but also in brachytherapy and newer intracoronary drug delivery systems.

Poster Session at The Society for Cardiac Angiography and Interventions, Houston, Texas, May 2001

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