Discrepancies in clavicle-to-carotid bifurcation length measurements for transcarotid artery revascularization using different imaging modalities

Objective: Transcarotid artery revascularization (TCAR) has emerged as an effective method for carotid artery stenting. However, anatomic eligibility for TCAR is most often limited by an inadequate clavicle-to-carotid bifurcation length of <5 cm. Preoperative clavicle-to-carotid bifurcation distances may be underestimated when using conventional straight-line measurements on computed tomographic angiography (CTA) imaging. We therefore compared clavicle-to-carotid bifurcation lengths as measured by straight-line CTA, center-line CTA, and intraoperative duplex ultrasound (US), to assess potential differences. Methods: We conducted a single-center, retrospective review of consecutive TCAR procedures performed between 2016 and 2019 for atherosclerotic carotid disease. For each patient, we compared clavicle-to-carotid bifurcation lengths measured by straight-line CTA, center-line CTA using TeraRecon image reconstruction, and intraoperative duplex US with neck extension and rotation. We further assessed patient and imaging characteristics in individuals with a >= 0.5 cm difference among the measurement methods. In particular, common carotid artery (CCA) tortuosity, defined as the inability to visualize the entire CCA from clavicle to carotid bifurcation on both a single coronal and sagittal imaging cut, was examined as a contributing factor for these discrepancies. Results: Of the 70 TCAR procedures identified, 46 had all three imaging modalities available for review. The median clavicle-to-carotid bifurcation length was found to be 6.4 cm (interquartile range [IQR], 5.4-6.7 cm) on straight-line CTA, 7.0 cm (IQR, 6.0-7.5 cm) on intraoperative duplex US, and 7.2 cm (IQR, 6.5-7.5 cm) on center-line CTA (P < .001). Patients with a >= 0.5 cm difference between their straight-line CTA and either their intraoperative duplex US or center-line CTA measurements were more likely to have tortuous CCAs (60.0% vs 19.1%; P = .01; 51.4% vs 0.0%; P = .01). There were no notable differences in age, gender, prior neck/cervical spine surgery, or neck immobility among these individuals. In patients with tortuous CCAs, duplex US and center-line CTA measurements added 1.0 cm (IQR, 0.6-1.5 cm) and 1.1 cm (IQR, 0.9-1.6 cm) more in length than straight-line CTA measurements, respectively. There was a strong linear correlation between the additional lengths provided by duplex US measurements and those provided by center-line CTA measurements for each individual within the tortuous CCA group (r = 0.83). Conclusions: The use of straight-line CTA during preoperative planning can underestimate the clavicle-to-carotid bifurcation lengths in patients undergoing carotid revascularization, particularly in those with tortuous CCAs. Both duplex US performed with extended-neck surgical positioning and center-line CTA provide similar and longer carotid length measurements, and should be utilized in patients with tortuous carotid vessels to better determine TCAR anatomic eligibility.