Intravascular ultrasound-based external elastic lamina measurements improve vertebral artery assessment over 2-dimensional digital subtraction angiography lumenogram

Vertebral artery stenosis is a condition amenable to treatment with stenting. To accurately size stents, angiography is the most used imaging technique despite its limitation as a lumenogram with few planes of imagery. The technique's deficiencies are especially apparent at the vertebral artery origin due to image obstruction by surrounding vessels as well as vessel tortuosity. By contrast, intravascular ultrasound (IVUS) can be used to measure the arterial external elastic lamina (EEL), which is closer to the true vessel size and often leads to larger and more appropriate stent sizes being chosen for more effective treatment. A retrospective measurement comparison study was conducted on eight patients with vertebral artery stenosis. 2D digital subtraction angiography (2D DSA) and IVUS images were taken along the vertebral artery for each patient, and the blood vessel diameter was measured using the two techniques along a continuous segment of the artery. Our results indicated a statistically significant discrepancy between the diameter measurements (p<0.05), with EEL measurements by IVUS showing a mean percent increase of 32.96%, or 1.19 mm, compared to 2D DSA lumen measurements. The significant measurement contrast between the two techniques can lead to smaller stent sizes being chosen, increasing the risk of restenosis and stent thrombosis due to malapposition. Sizing stents to the EEL is possible with IVUS imaging and can lead to more reliable treatment due to more secure strut placement on the tunica intima and a more complete expansion of the artery.