SCN5A mutations and the role of genetic background in the pathophysiology of Brugada syndrome

Background

Mutations in SCN5A are identified in approximately 20% to 30% of probands affected by Brugada syndrome (BrS). However, in familial studies, the relationship between SCN5A mutations and BrS remains poorly understood. The aim of this study was to investigate the association of SCN5A mutations and BrS in a group of large genotyped families.

Methods

Families were included if at least 3 family members were carriers of the SCN5A mutation, which was identified in the proband. Families were recruited from 12 tertiary centers in France between 1995 and 2020. Type 1 ST elevation was defined by ≥2 mm J-point elevation with coved ST segment and negative T wave.

Results

Forty-nine large families composed of 600 members including 304 mutation carriers (51%) were studied. The signature type I ECG was present in 160 mutation carriers (BrS-ECG+; 53%). In 42 families, we found 33 individuals affected by BrS but with a negative genotype (mutation-negative BrS-ECG+). Among them, 5 patients have an ECG suggestive of BrS but without the complete signature type I ECG. Among these 33 mutation-negative BrS-ECG+ individuals, 3 (9%), belonging to 3 different families, had a spontaneous type I ECG, whereas 28 had a type I ECG only after the administration of sodium channel blockers. Three of these 33 individuals (9%) had also experienced syncope. Mutation carriers had, on average, longer PR (190±36 ms vs 154±29 ms, p<0.0001) and QRS (107±19 vs 92±29 ms, p<0.0001) intervals than noncarriers, demonstrating that these mutations exerted functional effects.

Conclusions

Our results suggest that SCN5A mutations are not directly causal to the occurrence of a BrS-ECG+ and that genetic background may play a powerful role in the pathophysiology of BrS. These findings are consistent with the notion that the pathophysiology of BrS includes various elements beyond mutant sodium channels.

Funding Acknowledgement

Type of funding sources: None.

[An independent observatory in Vendée on ST-elevated acute myocardial infarction (the OVISCA Register). A Departmental evaluation of demographic trends, mortality and delays before treatment]

AIM

Mortality from acute myocardial infarction has been falling during the past 30 years. The aim of the study was to evaluate the temporal trends of demographics, mortality rates, and time to treatment in patients admitted for acute ST elevation myocardial infarction (STEMI) in Vendée.

PATIENTS AND METHODS

From 2008 to 2016, 1994 patients hospitalised in CHD Vendée for STEMI <48hours were included. Two groups were compared, 838 patients admitted between 2008 and 2011 (group 1), and 1156 admitted between 2013 and 2016 (group 2).

RESULTS

Between the 2 periods, mean age was comparable (63.8 vs. 64.4 years), the gender ratio decreased (from 3.15 to 2.79 ; P=0.25). The mean duration of hospital stay was 0.8 day shorter (P=0.008). Treatment at discharge was optimum in 97.5% patients versus 92% (P<0.001). Left ventricular ejection fraction was comparable (50.6% vs. 50.2%). There was a non-significant trend to a decrease in hospital mortality (from 6.3% to 4.4%; p=0.12), and 6-month mortality (from 6.9% to 5.9%; P=0.51). There was a reduction in the use of emergency call-outs (74.9% to 68.9%; P<0.01), but an increase in direct presentations from 44% to 48.7% (P<0.05). The time before calling was comparable (2.5hours vs. 2.3hours; P=04.7). The "door-to-balloon" time decreased (0.71 vs. 0.55hour; P<0.001). The mean time between pain and angioplasty increased (5.7 vs. 6.8hours; P<0.05).

CONCLUSIONS

In vendee, from 2011 to 2016, hospital and 6-month mortality of STEMI trend to decrease non-significantly. The door to balloon time decreased, although emergency call-out rates and delays did not. Considerable efforts are still required with respect to patient information and education. Our registry offers an excellent tool to improve practices, the aim being to ensure its integration in the CRAC-France PCI registry.