Exercise-Induced Brugada Phenocopy

Brugada phenocopy in a patient with acute pulmonary embolism presenting with recurrent syncope

Brugada phenocopy (BrP) refers to a group of clinical conditions that have etiologies distinct from Brugada syndrome (BrS). Although both demonstrate features of ST-segment elevation in the right precordial leads on the electrocardiogram (ECG), one must be distinguished from the other as their treatment options are different. We report a male patient who presented with recurrent syncope with a Brugada and a S1Q3T3 pattern on the ECG. Acute pulmonary embolism (APE) complicated by BrS was suspected. Twenty-four hours Holter monitoring did not demonstrate any evidence of ventricular arrhythmias. Computed tomography pulmonary angiogram confirmed the presence of an APE. He was treated with low molecular weight heparin and a repeat ECG taken the next day showed resolution of the Brugada and S1Q3T3 patterns. This case report illustrates that APE and BrS can present with similar clinical and electrocardiographic features of recurrent syncope and Brugada pattern, respectively.

Electrophysiological Mechanisms of Brugada Syndrome: Insights from Pre-clinical and Clinical Studies

Brugada syndrome (BrS), is a primary electrical disorder predisposing affected individuals to sudden cardiac death via the development of ventricular tachycardia and fibrillation (VT/VF). Originally, BrS was linked to mutations in the SCN5A, which encodes for the cardiac Na+ channel. To date, variants in 19 genes have been implicated in this condition, with 11, 5, 3, and 1 genes affecting the Na+, K+, Ca2+, and funny currents, respectively. Diagnosis of BrS is based on ECG criteria of coved- or saddle-shaped ST segment elevation and/or T-wave inversion with or without drug challenge. Three hypotheses based on abnormal depolarization, abnormal repolarization, and current-load-mismatch have been put forward to explain the electrophysiological mechanisms responsible for BrS. Evidence from computational modeling, pre-clinical, and clinical studies illustrates that molecular abnormalities found in BrS lead to alterations in excitation wavelength (λ), which ultimately elevates arrhythmic risk. A major challenge for clinicians in managing this condition is the difficulty in predicting the subset of patients who will suffer from life-threatening VT/VF. Several repolarization risk markers have been used thus far, but these neglect the contributions of conduction abnormalities in the form of slowing and dispersion. Indices incorporating both repolarization and conduction and based on the concept of λ have recently been proposed. These may have better predictive values than the existing markers.