Myocardial bridging is the most common congenital coronary anatomic variant. It occurs when a segment of an epicardial coronary artery takes an intramyocardial course — diving into the myocardium and resurfacing distally into the epicardial fat. The most frequent location is the mid segment of the LAD.
1 CCTA appearance & detection
CCTA is considered the best imaging tool for evaluating myocardial bridges — and is actually more sensitive than invasive angiography, which often misses short or shallow bridges. On CCTA, the artery can be directly visualized diving under a “bridge” of myocardium.
Bridge morphology classifies into two categories:
- “Touch-down” bridge. The coronary artery touches the myocardium but is not fully embedded.
- Deep bridge. The artery typically deviates toward the right ventricle and dives deep into the ventricular septum, with an overlying longitudinal muscle bundle from the right ventricular apex.
2 Plaque dynamics & diagnostic pitfalls
Bridges have unusual plaque characteristics:
- Protection from atherosclerosis. The physical systolic compression of the bridged segment prevents the deposition of lipid molecules — protecting the tunneled segment itself from atherosclerotic plaque.
- Upstream plaque. Conversely, increased shear wall stress predisposes the segment immediately upstream from the bridge to atherosclerosis.
Diagnostic pitfall: a myocardial bridge can occasionally mimic a non-calcified plaque with positive remodeling on CCTA. If you see “positive remodeling” but no plaque attenuation and an intramural course, think bridge.
3 Functional assessment
Because 85% of coronary blood flow naturally occurs during diastole, the dynamic systolic compression of the vessel (termed “milking” on invasive angiography) usually does not lead to a clinically significant reduction in diastolic perfusion.
- Transluminal Attenuation Gradient (TAG). On CCTA, evaluating TAG of the bridge correlates well with the actual systolic compression assessed by invasive angiography.
- CT-FFR limitations. Standard CT-FFR does not yield significant results when evaluating myocardial bridges. Novel functional techniques such as the instantaneous wave-free ratio (iFR) hold more promise and align better with patient symptoms.
4 Clinical significance & management
The vast majority of myocardial bridges are incidental findings, and most patients are completely asymptomatic. The direct association between bridges and true ischemia remains controversial — but in rare cases, specific bridges (deep, long) can be associated with angina, arrhythmia, or sudden death.
If a patient is symptomatic, medical management is the first line:
- β-blockers or calcium-channel blockers — improve coronary hemodynamics by decreasing heart rate (chronotropy) and contractility (inotropy)
- Nitrates are contraindicated — they worsen the dynamic compression
In extremely rare refractory cases:
- Percutaneous stenting — stabilizes the lumen against muscular compression
- Surgical myotomy — resecting the overlying muscle fibers
- CABG — bypassing the bridged segment