Fewer Vulnerable Plaques Hinted in LAD Myocardial Bridge Segment

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This is a summary of a preprint research study written by authors from Chiba University, Japan, on Research Square, provided to you by Medscape. This study has not yet been peer reviewed. Visit Research Square to find the full text of the study.

Key Takeaways

  • In a cohort of patients undergoing percutaneous coronary intervention (PCI) with near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS) imaging, 36% had a myocardial bridge (MB), a congenital anomaly in which a bundle of myocardium overlays an intramyocardial segment of artery that is normally epicardial — typically the lower anterior descending (LAD) coronary artery.

  • In myocardial bridge patients compared with the remaining patients, plaque burden was similar in the corresponding proximal segment and distal segment, but significantly smaller in the corresponding mid (bridged) segment.

  • Myocardial bridge patients showed significantly less plaque lipid content in both the proximal and mid segments, but the content was similar between the groups in the distal segment.

  • Maximum plaque burden and myocardial bridge were significant independent predictors of plaque lipid content in the proximal and mid segments.

Why This Matters

  • It is controversial whether MB hastens the progression of atherosclerotic plaque in the proximal LAD segment.

  • Although the research is unpublished and preliminary, it suggests that myocardial bridge is not always associated with greater plaque vulnerability, and therefore that patients with the anomaly do not necessarily have a worse prognosis. 

  • However, further study is warranted to clarify how myocardial bridge may be associated with plaque vulnerability, given that previous reports have suggested the anomaly is associated with risk of adverse events, such as arrhythmia, myocardial infarction, and sudden death in some patients.

Study Design

  • Presence of LAD myocardial bridge and related plaque characteristics were determined by grayscale IVUS and NIRS-IVUS imaging in patients undergoing PCI between March 2017 and May 2019 at Chiba University Hospital, Japan.

  • In patients with the anomaly, researchers measured proximal, middle (intramyocardial), and distal LAD artery segments and compared them with corresponding segments with the same average lengths in the cohort’s patients without myocardial bridge.

  • Plaque characteristics including maximum plaque burden were assessed in the LAD artery segments on grayscale IVUS images.

  • NIRS-IVUS imaging was used to measure plaque lipid content as the lipid core burden index (LCBI) and the maximum LCBI in any 4-mm region (maxLCBI4mm) in the proximal, middle, and distal segments.

Key Results

  • Of 116 patients for whom intravascular images were suitable for evaluation (due to acceptable degree of calcification and absence of prior coronary stent), of whom 80% were men, 42 had myocardial bridge by IVUS imaging.

  • Those with myocardial bridge were younger and less likely to be undergoing PCI of the LAD coronary artery.

  • The maximum plaque burden was:

    • Significantly greater in the proximal segment than in other segments in both groups.

    • Similar in the proximal segment (67.4% and 69.5%, P = .364) and the distal segment (45.9% and 47.5%, P = .737) in both groups.

    • Less in the middle segment in the bridge group than in the nonbridge group (40.6% vs 51.4%, P = .001).

  • Associated plaque lipid content (LCBI and maxLCBI4mm) was: