Is myocardial bridging related to syncope?

Is Myocardial Bridging Related to Syncope?

Yes, myocardial bridging can cause syncope, though most cases are benign and asymptomatic. When symptomatic, myocardial bridging may lead to syncope through myocardial ischemia-induced arrhythmias, particularly during exercise when increased heart rate and contractility worsen systolic compression of the bridged coronary segment 1, 2, 3.

Mechanism of Syncope in Myocardial Bridging

The pathophysiology involves systolic compression of the coronary artery (almost always the left anterior descending) by overlying muscle bundles, with delayed and incomplete vessel diameter recovery during diastole 1, 4. This compression is exacerbated during:

• Physical exertion - when increased sympathetic tone causes tachycardia and enhanced myocardial contractility, reducing diastolic filling time and worsening ischemia 2, 5
• Stress conditions - where dehydration and prolonged physical stress compound the ischemic burden 2

The resulting myocardial ischemia can trigger malignant ventricular arrhythmias, atrioventricular block, or sudden cardiac death, leading to syncope or cardiac arrest 1, 4.

Clinical Context and Risk Stratification

High-Risk Features Warranting Concern

Exertional syncope in young patients with myocardial bridging should be taken seriously, as this presentation pattern suggests exercise-induced ischemia 1, 2, 6. The European Society of Cardiology specifically identifies that sudden cardiac death typically occurs in males during or after physical activity 1.

• Myocardial bridging occurs in 30-50% of patients with hypertrophic cardiomyopathy and has been implicated as a cause of sudden cardiac death in this population 1, 4
• In isolated myocardial bridging without hypertrophic cardiomyopathy, syncope with signs of ischemia warrants aggressive evaluation even in children 6
• The presence of multiple simultaneous myocardial bridges may increase risk, as demonstrated in a marathon runner who experienced exercise-induced syncope and cardiac collapse 2

Diagnostic Evaluation for Symptomatic Patients

When myocardial bridging is suspected in a patient with syncope, the following workup is recommended:

• ECG exercise testing, dobutamine stress echocardiography, or myocardial perfusion scintigraphy to evaluate for inducible ischemia 1, 7, 4
• Coronary angiography to visualize the characteristic systolic compression and assess hemodynamic significance 1, 7
• Intracoronary Doppler flow velocity measurement in selected cases to obtain functional insight into diastolic flow abnormalities 1, 5

Management Algorithm

Initial Medical Therapy

Beta-blockers are first-line treatment for all symptomatic patients with myocardial bridging 1, 7, 4. They work by:

• Reducing heart rate (target resting heart rate 55-60 bpm) 7
• Decreasing myocardial contractility to reduce systolic compression 7, 4
• Prolonging diastole to improve coronary perfusion 7, 4

Metoprolol (extended-release metoprolol succinate preferred), carvedilol, or bisoprolol are appropriate choices 7.

Critical Pitfall to Avoid

Never prescribe nitrates for chest pain or syncope in myocardial bridging patients - they paradoxically worsen systolic compression by increasing myocardial contractility and can exacerbate symptoms 1, 7, 4.

Refractory Cases

For patients with continued symptoms despite adequate beta-blockade:

• Non-dihydropyridine calcium channel blockers (diltiazem or verapamil) as second-line therapy 7
• Surgical myotomy and/or coronary bypass for refractory cases 1
• Angioplasty or stenting may be considered, though surgery is generally preferred for definitive treatment 1

Athletic Participation Guidelines

• Asymptomatic competitive athletes with incidental myocardial bridging can participate in all competitive sports without restriction 7, 8
• Symptomatic athletes should restrict participation in high dynamic and static demand sports until symptoms resolve and stress testing normalizes 7
• There is no evidence supporting activity restriction in asymptomatic individuals without clinical evidence of ischemia 7, 8

Special Consideration: Hypertrophic Cardiomyopathy

In patients with hypertrophic cardiomyopathy, the relationship between myocardial bridging and syncope is more complex. While one report suggests short-tunneled myocardial bridges independently convey increased risk for cardiac arrest, potential biases in patient selection and the frequency of coronary bridging in surviving adults limit the power of this finding as a definitive risk factor 1. Most syncope in hypertrophic cardiomyopathy patients is neurocardiogenic rather than arrhythmic 1.

Prognosis

The long-term prognosis of isolated myocardial bridges appears excellent in most cases, but symptomatic patients—particularly those with exertional syncope—require careful evaluation and treatment to prevent ventricular tachyarrhythmias and sudden cardiac death 1, 5.