Absence of pathognomonic or inflammatory patterns in cardiac biopsies from patients with Brugada syndrome.

BACKGROUND: Brugada syndrome (BrS) is characterized by the presence of coved ST-segment elevations in the right precordial leads (so-called type I ECG) and additional clinical features. Caused by cardiac ion channel gene mutations, BrS may be associated with ventricular and atrial conduction disturbances as well as ventricular fibrillation. Recent studies have discussed whether BrS is merely a primary electric disorder or whether inflammatory or other histopathologic abnormalities in the right ventricle (RV) underlie the ECG phenotype.

METHODS AND RESULTS: We retrospectively analyzed BrS biopsy samples from 21 unrelated patients for histopathologic abnormalities (hypertrophy, fibrosis, inflammation, fatty tissue) together with the patients' clinical, genetic, and imaging data. Eleven patients (52%) had normal RV imaging (by angiography, echocardiography, or cardiac MRI). Results of myocardial biopsies were normal in 3 patients (14%) and revealed mostly moderate abnormalities in the others. Four patients (19%) had predominant fatty tissue in the RV myocardium. Using immunohistochemistry and conventional tissue staining, we could not detect inflammatory tissue changes, an observation compatible with the clinical absence of signs for myocarditis.

CONCLUSIONS: Imaging and histopathologic evaluation may detect moderate but uncharacteristic cardiac abnormalities in patients with BrS. None of the patients had arrhythmogenic RV cardiomyopathy or overt myocarditis. Only in a small subset did predominant histopathologic abnormalities in the biopsy samples of the RV outflow tract occur that could provide a link to the ECG phenotype. A variety of mechanisms, including genetic and structural RV alterations, may underlie the Brugada ECG phenotype.