What is the most appropriate test to identify the cause of syncope in a patient with electrocardiogram (ECG) findings suggestive of Brugada syndrome?

From the Guidelines

The most appropriate test to identify the cause of syncope in a patient with ECG findings suggestive of Brugada syndrome is an electrophysiology study (EPS) with programmed electrical stimulation. This invasive procedure involves placing catheters in the heart to record electrical activity and deliberately attempt to induce arrhythmias under controlled conditions. During the study, the electrophysiologist will deliver programmed electrical stimuli to evaluate if ventricular arrhythmias can be triggered, which would suggest that the patient's syncope was likely due to a ventricular tachyarrhythmia. The EPS is particularly valuable in Brugada syndrome because it can help risk-stratify patients and determine if an implantable cardioverter-defibrillator (ICD) is warranted for prevention of sudden cardiac death, as recommended by the 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1.

Key Points

• The EPS is especially indicated in patients with Brugada syndrome who have experienced syncope, as this combination significantly increases the risk of life-threatening arrhythmias.
• The underlying mechanism of Brugada syndrome involves sodium channel dysfunction leading to electrical heterogeneity in the right ventricular outflow tract, which creates a substrate for reentrant ventricular arrhythmias that can cause syncope or sudden death.
• According to the guidelines for the diagnosis and management of syncope, an electrophysiological study may be performed in selected cases of patients with Brugada syndrome 1.
• The 2018 guideline also suggests that in patients with suspected Brugada syndrome, a pharmacological challenge using a sodium channel blocker can be useful for diagnosis, and an electrophysiological study with programmed ventricular stimulation may be considered for further risk stratification 1.

Comparison of Options

• Cardiac catheterization is not the most appropriate test for identifying the cause of syncope in Brugada syndrome, as it is primarily used to diagnose coronary artery disease.
• Cardiac MRI may be useful in evaluating the structure of the heart, but it is not the primary test for diagnosing Brugada syndrome.
• Stress testing is not typically used to diagnose Brugada syndrome, as the condition is characterized by abnormal ECG findings at rest.
• Electrophysiology study is the most appropriate test, as it can help diagnose and risk-stratify patients with Brugada syndrome, as supported by the guidelines 1.

From the Research

Diagnostic Approach for Syncope in Brugada Syndrome

The patient's ECG findings, including a small positive deflection buried in the end of the QRS complex, T wave inversions, and a prolonged S wave upstroke in leads V1–V3, are suggestive of Brugada syndrome. To identify the cause of syncope in this patient, the following tests can be considered:

• Electrophysiology study (EPS): This test can help determine if the patient has a cardiogenic cause of syncope, such as ventricular arrhythmias, and can also assess the risk of sudden cardiac death 2, 3.
• Class-I antiarrhythmic drug test: This test can be used to unmask the diagnostic coved-type ECG pattern in patients with Brugada syndrome, especially if the pattern is not spontaneously present 4, 5.
• Cardiac MRI: While not directly mentioned in the context of Brugada syndrome diagnosis, cardiac MRI can be useful in evaluating structural heart disease, which may be relevant in some cases of syncope.
• Stress testing: This test is not typically used to diagnose Brugada syndrome or evaluate syncope in this context.
• Cardiac catheterization: This test is not typically used to diagnose Brugada syndrome or evaluate syncope in this context.

Key Considerations

• The EPS is a valuable tool in assessing the risk of major events, such as ventricular arrhythmias and sudden cardiac death, in patients with Brugada syndrome and syncope 2, 3.
• The class-I antiarrhythmic drug test can be used to unmask the diagnostic ECG pattern in patients with Brugada syndrome, especially if the pattern is not spontaneously present 4, 5.
• Accurate classification of syncope is crucial in patients with Brugada syndrome, as it can help identify those at higher risk of major events 2, 3.