Brugada ECG pattern :a physiopathological prospective study based on clinical, electrophysiological, angiographic, and genetic findings.

Main results

114 consecutive patients matched in age underwent prospectively cardiac catheterization and quantitative biventricular contrast angiography to rule out a structural heart disease. Studied population included: 51 patients with a BrS-ECG (BrS group, 7F, 44M, 43 ± 11 y)  who had a spontaneous or ajmaline-induced BrS coved type ECG, 49 patients with localized ARVD/C but without ST segment elevation in the right precordial leads (14F, 35M, 39±13y), and 14 control patients (7 F, 7 M, 38 ± 16 y). Among BrS group, the authors identified three main angiographic phenotypes: BrS group I = patients with normal RV (n = 15, 29%); BrS group II = patients with segmental RV wall motion abnormalities but no structural arguments for ARVD/C (n = 26, 51%); BrS group III = patients with localized abnormalities suggestive of focal ARVD/C (n = 10, 20%).
Seventy-one percent of patients with BrS-ECG had abnormal RV wall motion. In BrS group III, 8/10 patients (16% of BrS patients) finally fulfilled international ESC/WHF 2000 ARVD/C criteria and 5/10 (10% of BrS patients) fulfilled BrS diagnostic criteria. An overlap was observed in 4 patients (8% of BrS patients) who fulfilled both ARVD/C and BrS criteria. Among the 45 genotyped patients, only one presented a SCN5A mutation, whereas a TRPM4 mutation was found in another patient. Both belonged to BrS group II. MOG1 gene analysis was negative for all patients, as were PKP2, DSP, DSG2, and DSC2 analyzes performed in BrS group III.

Discussion

This is the first study to show prospectively an overlap between BrS and ARVD/C.
The main finding of the study is that 71% of patients with a BrS-ECG had abnormal RV wall motion and 16% had structural alterations corresponding to localized (anteroapical and/or diaphragmatic) ARVD/C. Moreover, 8% of BrS-ECG patients fulfilled both BrS and ARVD/C criteria.
These findings support the hypothesis of an overlap between BrS and localized or concealed forms of ARVD/C, but also that Brugada ECG pattern is not specific of a pathophysiological entity, i.e., BrS, but can be due to other conditions such as myocarditis or localized RV cardiomyopathy. BrS ECG pattern may be an indicator of ARVC, particularly in its clinically concealed phase, thus requiring morphological RV evaluation, such as MRI, contrast echocardiography and/or contrast angiography.
As pointed out by the authors this overlap between BrS and ARVD/C does not mean that these two diseases are the same one, but that a substantial proportion of patients with a Brugada ECG pattern present RV structural alterations.
In this study genetic screening was poorly contributive for both diseases. One of the explanations of the low prevalence of SCN5A mutations in thus series may lie in the high proportion of structural abnormalities and of localized ARVD/C.