Optical coherence tomography and intravascular ultrasound assessment of the anatomic size and wall thickness of a muscle bridge segment.

OBJECTIVE

To use optical coherence tomography (OCT) and intravascular ultrasound (IVUS) in assessing myocardial bridging (MB) vessel size and wall thickness.

BACKGROUND

During stent implantation, MB is associated with complications, especially perforation.

METHODS

OCT and IVUS were performed in 56 patients with typical angiographic "milking" from November 2016 to May 2017. The vessel area and thickness in the MB segments and adjacent proximal and distal reference segments were measured and compared with eight normal left anterior descending (LAD) segment (no atherosclerosis in a segment that was at least 20 mm long and that began ~40 mm distal to the LAD ostium).

RESULTS

Compared with the reference vessel size distal to the MB segment (6.3 ± 1.8 mm ), the IVUS-measured size of the tunneled vessel during diastole was significantly smaller (6.0 ± 1.9 mm , p < 0.05) (remodeling index = 0.79 ± 0.18). The minimum intramyocardial arterial wall thickness was 0.16 ± 0.02 mm, significantly thinner than that of the mean reference (0.22 ± 0.03 mm, p < 0.001). The location of the thinnest arterial wall was in the distal and middle MB segments in 45 (80.4%) and 11 (19.6%) patients, respectively, and was not related to the degree of systolic compression or remodeling index. The walls of the middle and distal MB subsegments, but not of the proximal MB subsegment, were thinner than that of the comparison group of normal LADs.

CONCLUSION

The coronary vessel involved in an MB is both smaller and thinner than that of the adjacent non-MB segment. This may explain the increased frequency and severity of coronary perforation during stent implantation.