Severe Myocardial Bridging Without Obstructive Coronary Artery Disease Presenting as Non-ST-Elevation Myocardial Infarction: A Management Challenge in Sinus Bradycardia

Myocardial bridging (MB) is an anomaly in which a segment of a coronary artery takes an intramyocardial route. It can increase the risk of cardiovascular complications. Beta-blockers (BB) are usually the first line of treatment, and management may be challenging in patients with bradycardia. A 53-year-old male former smoker with hypertension and dyslipidemia presented to the emergency department complaining of retrosternal chest pain that awakened him from sleep and dyspnea. Upon evaluation, an electrocardiogram (ECG) revealed sinus bradycardia with T-wave inversions in leads II, III, aVF, and V3-V6. High-sensitivity troponin peaked at 335 pg/mL (4-79 pg/mL), and the patient was admitted with a diagnosis of non-ST-elevation myocardial infarction (NSTEMI). He was given 324 mg of aspirin, a heparin drip was started, and pain improved after sublingual nitroglycerin. Transthoracic echocardiogram (TTE) demonstrated a preserved left ventricular function without wall motion abnormalities. Coronary angiography identified a MB in the mid-left anterior descending coronary artery (LAD) without atherosclerotic disease. Coronary CT angiography described a 20 mm long and 7 mm deep MB with 90%-99% dynamic obstruction during end-systole. After a Heart Team meeting, the decision was to attempt medical management with metoprolol as tolerated. The patient remained angina-free and asymptomatic. A stress test prior to discharge was negative for ischemia or recurrent pain. After one-year follow-up, he has remained asymptomatic, with repeated unremarkable stress tests after reduction of BB dose. Severe MB may be associated with significant cardiovascular complications, including NSTEMI. Treatment poses a challenge in patients with bradycardia. This case illustrates that cautious beta-blocker therapy may be a feasible option in selected patients.