Cardiovasc Imaging Asia.  2018 Jul;2(3):129-134. 10.22468/cvia.2018.00017.

Attenuation Drop of Intra-Mural Coronary Segment Observed at Diastolic Phase of Coronary CT Angiography Predicts Significant Systolic Compression of Myocardial Bridge

• Yu M
• Li W
• Li Y
• Zhang J

• KMID: 2524873
• DOI: http://doi.org/10.22468/cvia.2018.00017

Abstract

Objective
To study the diagnostic value of percentage attenuation drop measured by coronary computed tomography angiography (CTA) for identifying significant dynamic compression of myocardial bridge (MB).
Materials and Methods
Patients with MB-confirmed vessels who underwent retrospectively electrocardiogram-gated coronary CTA were reviewed. The average attenuation of the MB segment (attenuation _MB) as well as the segment from the vessel ostium to MB entrance point (attenuation _proximal) was calculated. The difference in Hounsfield unit between attenuation proximal and attenuation _MB was divided by attenuation _proximal to obtain the percentage attenuation drop of the mural coronary artery. The percentage attenuation drop of MB vessel, length of MB, and depth of MB were measured and correlated with the presence and degree of dynamic compression observed at the invasive coronary angiography. Systolic compression ≥50% was considered significant.
Results
135 patients with CTA-confirmed MB lesions were included. The percentage of attenuation drop of MB segment (20.2±11.9% vs. 7.7±7.9%, p<0.001) as well as MB length (25.4±11.6 mm vs. 17.3±6.2 mm, p=0.001) was largest in the subgroup of significant dynamic compression and smallest in the subgroup of no dynamic compression. ROC curve analysis determined the best cutoff value of percentage of attenuation drop as 15% (area under curve=0.75, 95% confidence interval=0.668–0.82, p<0.001), which yielded high diagnostic accuracy (73.3%, 99/135).
Conclusion
The percentage attenuation drop of the MB segment significantly correlated with the extent of dynamic compression of the MB. Percentage attenuation drop ≥15% (cutoff value) has high diagnostic accuracy (73.3%, 99/135) for identifying significant dynamic compression of a MB.

Keyword

Coronary artery disease; Multidetector computed tomography; Angiography