Unmasking a Hidden Bridge: Exercise-Induced Right Bundle Branch Block Without Ischemia

Area of Science:

• Cardiology
• Clinical Medicine
• Diagnostic Imaging

Background:

• Myocardial bridging (MB) is a congenital anomaly where a segment of coronary artery travels through the heart muscle.
• While often benign, MB can rarely be linked to myocardial ischemia or cardiac arrhythmias.
• Exercise-induced conduction abnormalities in MB are uncommon and not well-understood.

Purpose of the Study:

• To report a rare case of exercise-induced right bundle branch block (RBBB) in an asymptomatic patient with myocardial bridging.
• To differentiate between ischemic and non-ischemic causes of conduction abnormalities during exercise in MB patients.

Main Methods:

• Case presentation of a 69-year-old male with transient RBBB during treadmill stress testing.
• Coronary computed tomography angiography (CCTA) to evaluate for myocardial bridging and coronary artery disease.

Main Results:

• The patient experienced transient RBBB at peak exertion, resolving immediately during recovery, without symptoms of ischemia.
• CCTA revealed a superficial myocardial bridge in the mid-left anterior descending artery, with no significant luminal narrowing or atherosclerosis.
• Findings indicated a benign, rate-dependent conduction delay rather than an ischemic event.

Conclusions:

• This case highlights a rare association between myocardial bridging and exercise-induced RBBB.
• Recognizing non-ischemic conduction phenomena is crucial to prevent unnecessary invasive cardiac investigations.