Lower 24-hour Holter-Derived Heart Rates Suggest Brugada Syndrome: Study of the Family

Background: Brugada syndrome (BrS) often occurs among members of one family but factors facilitating the diagnosis among family members are poorly known. Methods: We assessed Holter electrocardiograms (ECG) and echocardiograms of relatives of SCA victim with a post-mortem diagnosis of BrS. Due to young age (n=2) or intensive care unit treatment (n=l), available Holter/echocardiogram findings, were not included in the analysis. Results: The study group included 15 patients, 7 with BrS (including 2 children) and 8 persons with excluded BrS, based on ajmaline challenge. The mean age of studied adults was 34.0±11.8 (22-58) years, female consisted 30.8% (n=4), and these characteristics did not differ in patients with or without BrS. Adult BrS patients were characterized by lower mean, minimum and maximum heart rate (HR) obtained from Holter monitoring: 62±6 (median, interquartile range [IQRJ: 61, 57-68) beats per minute (bpm) vs. 75±7 (median, IQR: 76, 68-80) bpm, p=0.017; 46±5 (median, IQR: 44, 42-50) bpm vs. 54±5 (median, IQR: 55, 50-58) bpm, p=0.017 and 94±9 (median, IQR: 98,85-100) bpm vs. 121 ±9 (median, IQR: 122,115-130) bpm, p=0.007, respectively. On the other hand, we did not observe any difference in regard to supraventricular (p=0.481) or ventricular premature extrasystolic beats (p=0.296) between studied adult patients with and without BrS. Moreover, studied with echocardiography adult patients with (n=5) or without (n=6) BrS did not differ in regard to left ventricular (LV) ejection fraction (p=0.519), LV end-diastolic/end-systolic diameter (p=0.779 and p=0.583), left atrium diameter (p=0.364) or interventricular septum thickness (p=0.729). BrS was identified in at least one first-, second- and third-degree relative of SCA victim. Conclusions: BrS patients within one family are characterized by lower HR, which could be explained by increased vagal activity and may suggest BrS. In terms of SCA victims due to BrS, family screening beyond first-degree relatives may be reasonable.