Objectives: To study the diagnostic value of transluminal attenuation gradient (TAG) measured by coronary computed tomography angiography (CCTA) for identifying relevant dynamic compression of myocardial bridge (MB).
Methods: Patients with confirmed MB who underwent both CCTA and ICA within one month were retrospectively included. TAG was defined as the linear regression coefficient between luminal attenuation and distance. The TAG of MB vessel, length and depth of MB were measured and correlated with the presence and degree of dynamic compression observed at ICA. Systolic compression ≧50 % was considered significant.
Results: 302 patients with confirmed MB lesions were included. TAG was lowest (-17.4 ± 6.7 HU/10 mm) in patients with significant dynamic compression and highest in patients without MB compression (-9.5 ± 4.3 HU/10 mm, p < 0.001). Linear correlation revealed relation between the percentage of systolic compression and TAG (Pearson correlation, r = -0.52, p < 0.001) and no significant relation between the percentage of systolic compression and MB depth or length. ROC curve analysis determined the best cut-off value of TAG as -14.8HU/10 mm (area under curve = 0.813, 95 % confidence interval = 0.764-0.855, p < 0.001), which yielded high diagnostic accuracy (82.1 %, 248/302).
Conclusions: The degree of ICA-assessed systolic compression of MB significantly correlates with TAG but not MB depth or length.
Key points: • TAG is associated with the extent of dynamic compression of MB. • TAG is superior to depth and length for identifying dynamic compression. • Cut-off value of TAG as -14.8HU/10 mm yielded high predictive value.
Keywords: Computed tomography; Coronary angiography; Coronary artery disease; Myocardial bridge; Transluminal attenuation gradient.